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Sökning: WFRF:(Passoth Volkmar)

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1.
  • Bakeeva, Albina, et al. (författare)
  • Effect of solid-state fermentation with Arxula adeninivorans or Hypocrea jecorina (anamorph Trichoderma reesei) on hygienic quality and in-vitro digestibility of banana peels by mono-gastric animals
  • 2017
  • Ingår i: Livestock Science. - : Elsevier BV. - 1871-1413 .- 1878-0490. ; 199, s. 14-21
  • Tidskriftsartikel (refereegranskat)abstract
    • This study evaluated the effectiveness of solid-state fermentation with Arxula adeninivorans or Hypocrea jecorina to improve hygienic quality and digestibility of banana peels by mono-gastric animals. Green peels of cooking bananas (Musa AAA-group) were solid-state fermented in ziploc plastic bags for 14 d either non inoculated or inoculated with A. adeninivorans or H. jecorina. Colonies of aerobic bacteria, lactic acid bacteria, Enterobacteriaceae, yeasts and moulds were enumerated. In-vitro digestibility (total tract and pre-caecal) of dry matter (DM), organic matter (OM) and crude protein (CP) was also determined. Solid-state fermentation significantly improved (P < 0.05) in-vitro total tract digestibility (9.9% for DM and 10.1% for OM), and in-vitro pre-caecal digestibility (25.0% for DM, 30.9% for OM and 74.5% for CP); however, no significant effect (P > 0.05) due to inoculation was observed. Conversely, inoculation (with A. adeninivorans or H. jecorina) significantly improved (P < 0.05) the hygienic quality; with lower (P < 0.05) aerobic bacteria, Enterobacteriaceae and mould counts than the non-inoculated treatment. However, H. jecorina triggered a significantly superior (P < 0.05) improvement in both hygienic quality and in-vitro pre-caecal digestibility than A. adeninivorans.
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2.
  • Bakeeva, Albina, et al. (författare)
  • The Potential of Kluyveromyces marxianus to Produce Low-FODMAP Straight-Dough and Sourdough Bread: a Pilot-Scale Study
  • 2021
  • Ingår i: Food and Bioprocess Technology. - : Springer Science and Business Media LLC. - 1935-5130 .- 1935-5149. ; 14, s. 1920-1935
  • Tidskriftsartikel (refereegranskat)abstract
    • Diets low in fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs) can help reduce symptoms in 50 to 80% of patients suffering from irritable bowel syndrome. Patients are, therefore, often advised to avoid products contributing to FODMAP intake, such as cereal grain products. However, these products are nutritious staple foods and avoiding their consumption may result in nutritional deficiencies. The development of low-FODMAP, high-fiber cereal grain products is therefore desirable. This pilot-scale study shows that Kluyveromyces marxianus CBS6014 (K. marxianus) results in more fructan hydrolysis and a significantly lower final fructan level in white and whole-grain toast bread as well as in rye sourdough bread compared to a commercial Saccharomyces cerevisiae baking strain. Moreover, combined fructan and fructose levels in white and whole-grain bread prepared with K. marxianus remained well below the threshold concentration for low-FODMAP products. In addition to reducing fructan levels, K. marxianus in rye sourdough bread also positively impacted bread height. Whereas further follow-up studies are needed to assess the potential of K. marxianus for bread production fully, our study suggests that this yeast species may open exciting novel routes for the production of low-FODMAP, high-fiber products.
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3.
  • Bakeeva, Albina, et al. (författare)
  • Yeasts and bacteria associated with kocho, an Ethiopian fermented food produced from enset (Ensete ventricosum)
  • 2019
  • Ingår i: Antonie van Leeuwenhoek. - : Springer Science and Business Media LLC. - 0003-6072 .- 1572-9699. ; 112, s. 651-659
  • Tidskriftsartikel (refereegranskat)abstract
    • Enset (Ensete ventricosum) is the basis of the staple food consumed by about 20% of the Ethiopian population. Kocho is one of the food products generated from enset by spontaneous fermentation of decorticated and pulverized pseudostem and corm sections. We isolated culturable microbes associated with kocho from different stages of fermentation. Twelve yeast species, six lactic acid bacteria (LABs) species and eleven species of aerobic bacteria were identified by sequencing ITS/D1D2 regions of 26S rDNA of yeasts and 16S rDNA of bacteria, respectively. More yeast species were identified in fresh (fermented for 2-5days) kocho, compared to long-term (7-12months) fermented kocho, while we observed an opposite trend for LABs. In fresh kocho, the most frequently isolated yeast species were Pichia exigua, Galactomyces geotrichum, and Pichia fermentans. From mid-term (3-4months) kocho most frequently Candida cabralensis, G. geotrichum, and Candida ethanolica were isolated. In the long-term fermentations, the most frequently isolated yeast was Saturnispora silva. Lactobacillus plantarum was the most frequently isolated LAB in both fresh and mid-term kocho. In long-term fermented kocho, Acetobacter pasteurianus and L. plantarum were most frequently isolated. L. plantarum was consistently isolated from all the three stages of fermentation. Aerobic bacteria in fresh kocho were mostly gram-negative, with Raoultella planticola and Pantoea agglomerans being the most frequently isolated species. In long-term fermented kocho, mainly gram-positive, spore-forming bacteria of the genus Bacillus were found, among them also species of the Bacillus cereus group, Bacillus anthracis and Bacillus thurigiensis.
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4.
  • Blomqvist, Johanna, et al. (författare)
  • Dekkera bruxellensis-spoilage yeast with biotechnological potential, and a model for yeast evolution, physiology and competitiveness
  • 2015
  • Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1356 .- 1567-1364. ; 15, s. 9-
  • Forskningsöversikt (refereegranskat)abstract
    • Dekkera bruxellensis is a non-conventional yeast normally considered a spoilage organism in wine (off-flavours) and in the bioethanol industry. But it also has potential as production yeast. The species diverged from Saccharomyces cerevisiae 200 mya, before the whole genome duplication. However, it displays similar characteristics such as being Crabtree-and petite positive, and the ability to grow anaerobically. Partial increases in ploidy and promoter rewiring may have enabled evolution of the fermentative lifestyle in D. bruxellensis. On the other hand, it has genes typical for respiratory yeasts, such as for complex I or the alternative oxidase AOX1. Dekkera bruxellensis grows more slowly than S. cerevisiae, but produces similar or greater amounts of ethanol, and very low amounts of glycerol. Glycerol production represents a loss of energy but also functions as a redox sink for NADH formed during synthesis of amino acids and other compounds. Accordingly, anaerobic growth required addition of certain amino acids. In spite of its slow growth, D. bruxellensis outcompeted S. cerevisiae in glucose-limited cultures, indicating a more efficient energy metabolism and/or higher affinity for glucose. This review tries to summarize the latest discoveries about evolution, physiology and metabolism, and biotechnological potential of D. bruxellensis.
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5.
  • Blomqvist, Johanna, et al. (författare)
  • Fermentation characteristics of Dekkera bruxellensis strains
  • 2010
  • Ingår i: Applied Microbiology and Biotechnology. - New York, USA : Springer. - 0175-7598 .- 1432-0614. ; 87:4, s. 1487-1497
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of pH, temperature and carbon source (glucose and maltose) on growth rate and ethanol yield of Dekkera bruxellensis was investigated using a full-factorial design. Growth rate and ethanol yield were lower on maltose than on glucose. In controlled oxygen-limited batch cultivations, the ethanol yield of the different combinations varied from 0.42 to 0.45 g (g glucose)(-1) and growth rates varied from 0.037 to 0.050 h(-1). The effect of temperature on growth rate and ethanol yield was negligible. It was not possible to model neither growth rate nor ethanol yield from the full-factorial design, as only marginal differences were observed in the conditions tested. When comparing three D. bruxellensis strains and two industrial isolates of Saccharomyces cerevisiae, S. cerevisiae grew five times faster, but the ethanol yields were 0-13% lower. The glycerol yields of S. cerevisiae strains were up to six-fold higher compared to D. bruxellensis, and the biomass yields reached only 72-84% of D. bruxellensis. Our results demonstrate that D. bruxellensis is robust to large changes in pH and temperature and may have a more energy-efficient metabolism under oxygen limitation than S. cerevisiae.
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6.
  • Blomqvist, Johanna, et al. (författare)
  • Fermentation of lignocellulosic hydrolysate by the alternative industrial ethanol yeast Dekkera bruxellensis
  • 2011
  • Ingår i: Letters in Applied Microbiology. - Malden, USA : Wiley-Blackwell. - 0266-8254 .- 1472-765X. ; 53:1, s. 73-78
  • Tidskriftsartikel (refereegranskat)abstract
    • Aim: Testing the ability of the alternative ethanol production yeast Dekkera bruxellensis to produce ethanol from lignocellulose hydrolysate and comparing it to Saccharomyces cerevisiae.Methods and Results: Industrial isolates of D. bruxellensis and S. cerevisiae were cultivated in small-scale batch fermentations of enzymatically hydrolysed steam exploded aspen sawdust. Different dilutions of hydrolysate were tested. None of the yeasts grew in undiluted or 1 : 2 diluted hydrolysate [final glucose concentration always adjusted to 40 g l(-1) (0.22 mol l(-1))]. This was most likely due to the presence of inhibitors such as acetate or furfural. In 1 : 5 hydrolysate, S. cerevisiae grew, but not D. bruxellensis, and in 1 : 10 hydrolysate, both yeasts grew. An external vitamin source (e.g. yeast extract) was essential for growth of D. bruxellensis in this lignocellulosic hydrolysate and strongly stimulated S. cerevisiae growth and ethanol production. Ethanol yields of 0 42 +/- 0 01 g ethanol (g glucose)(-1) were observed for both yeasts in 1 : 10 hydrolysate. In small-scale continuous cultures with cell recirculation, with a gradual increase in the hydrolysate concentration, D. bruxellensis was able to grow in 1 : 5 hydrolysate. In bioreactor experiments with cell recirculation, hydrolysate contents were increased up to 1 : 2 hydrolysate, without significant losses in ethanol yields for both yeasts and only slight differences in viable cell counts, indicating an ability of both yeasts to adapt to toxic compounds in the hydrolysate.Conclusions: Dekkera bruxellensis and S. cerevisiae have a similar potential to ferment lignocellulose hydrolysate to ethanol and to adapt to fermentation inhibitors in the hydrolysate.Significance and Impact of the study: This is the first study investigating the potential of D. bruxellensis to ferment lignocellulosic hydrolysate. Its high competitiveness in industrial fermentations makes D. bruxellensis an interesting alternative for ethanol production from those substrates.
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7.
  • Blomqvist, Johanna, et al. (författare)
  • Oleaginous yeast as a component in fish feed
  • 2018
  • Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • This study investigates the replacement of vegetable oil (VO) in aquaculture feed for Arctic char (Salvelinus alpinus) with oil produced by the oleaginous yeast Lipomyces starkeyi grown in lignocellulose (wheat straw) hydrolysate. VO is extensively used to partially replace fish oil in aquaculture feed, which can be seen as non-sustainable. VO itself is becoming a limited resource. Plant oils are used in many different applications, including food, feed and biodiesel. Its replacement in non-food applications is desirable. For this purpose, yeast cells containing 43% lipids per g dry weight were mechanically disrupted and incorporated into the fish feed. There were no significant differences in this pilot study, regarding weight and length gain, feed conversion ratio, specific growth rate, condition factor and hepatosomatic index between the control and the yeast oil fed group. Fatty and amino acid composition of diet from both groups was comparable. Our results in fish demonstrate that it is possible to replace VO by yeast oil produced from lignocellulose, which may broaden the range of raw materials for food production and add value to residual products of agriculture and forestry.
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8.
  • Blomqvist, Johanna, et al. (författare)
  • Physiological requirements for growth and competitiveness of Dekkera bruxellensis under oxygen-limited or anaerobic conditions
  • 2012
  • Ingår i: Yeast. - : Wiley. - 1097-0061 .- 0749-503X. ; 29:7, s. 265-274
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of glucose and oxygen limitation on the growth and fermentation performances of Dekkera bruxellensis was investigated in order to understand which factors favour its propagation in ethanol or wine plants. Although D. bruxellensis has been described as a facultative anaerobe, no growth was observed in mineral medium under complete anaerobiosis while growth was retarded under severe oxygen limitation. In a continuous culture with no gas inflow, glucose was not completely consumed, most probably due to oxygen limitation. When an air/nitrogen mixture (O-2-content ca. 5%) was sparged to the culture, growth became glucose-limited. In co-cultivations with Saccharomyces cerevisiae, ethanol yields/g consumed sugar were not affected by the co-cultures as compared to the pure cultures. However, different population responses were observed in both systems. In oxygen-limited cultivation, glucose was depleted within 24 h after challenging with S. cerevisiae and both yeast populations were maintained at a stable level. In contrast, the S. cerevisiae population constantly decreased to about 1% of its initial cell number in the sparged glucose-limited fermentation, whereas the D. bruxellensis population remained constant. To identify the requirements of D. bruxellensis for anaerobic growth, the yeast was cultivated in several nitrogen sources and with the addition of amino acids. Yeast extract and most of the supplied amino acids supported anaerobic growth, which points towards a higher nutrient demand for D. bruxellensis compared to S. cerevisiae in anaerobic conditions. Copyright (c) 2012 John Wiley & Sons, Ltd.
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9.
  • Blomqvist, Johanna, et al. (författare)
  • Temperature-dependent changes in the microbial storage flora of birch and spruce sawdust
  • 2014
  • Ingår i: Biotechnology and Applied Biochemistry. - : Wiley. - 0885-4513 .- 1470-8744. ; 61, s. 58-64
  • Tidskriftsartikel (refereegranskat)abstract
    • Sawdust can be used to make pellets (biofuel) and particle boards and as a potential lignocellulose feedstock in bioethanol production. Microbial activity can affect sawdust quality; hence, we monitored the microbial population in birch- and spruce sawdust after 3 months' storage at various temperatures. Species composition was similar on both materials but was strongly influenced by temperature. Bacteria were present on all materials at all conditions: on birch, 2.8x10(8), 1.1x10(8), and 8.8x10(6), and on spruce, 4.1x10(8), 5.6x10(7), and 1.5x10(8)CFU/g DM, at 2, 20, and 37 degrees C, respectively. Dominant bacteria at 2, 20, and 37 degrees C were Pseudomonas spp. (some Enterobacteriaceae spp. present), Luteibacter rhizovicinus, and Fulvimonas sp., respectively. Pseudomonas spp. were absent at 20 degrees C. Among microfungi, yeasts dominated at 2 degrees C but were absent at 37 degrees C, whereas molds dominated at 20 and 37 degrees C. Common yeasts included Cystofilobasidium capitatum, Cystofilobasidium infirmominiatum, Candida saitoana, Candida oregonensis, and Candida railenensis. Ophiostoma quercus was a common mold at 2 and 20 degrees C, whereas the human pathogens Aspergillus fumigatus and Paecilomyces variotii dominated at 37 degrees C. Attempts to influence the microflora by addition of the biocontrol yeasts, Wickerhamomyces anomalus and Scheffersomyces stipitis, were unsuccessful, as their growth in sawdust was poor to absent.
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10.
  • Blomqvist, Johanna, et al. (författare)
  • The effect of a combined biological and thermo-mechanical pretreatment of wheat straw on energy yields in coupled ethanol and methane generation
  • 2015
  • Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 194, s. 7-13
  • Tidskriftsartikel (refereegranskat)abstract
    • Ethanol and biogas are energy carriers that could contribute to a future energy system independent of fossil fuels. Straw is a favorable bioenergy substrate as it does not compete with food or feed production. As straw is very resistant to microbial degradation, it requires a pretreatment to insure efficient conversion to ethanol and/or methane. This study investigates the effect of combining biological pretreatment and steam explosion on ethanol and methane yields in order to improve the coupled generation process. Results show that the temperature of the steam explosion pretreatment has a particularly strong effect on possible ethanol yields, whereas combination with the biological pretreatment showed no difference in overall energy yield. The highest overall energy output was found to be 10.86 MJ kg VS-1 using a combined biological and steam explosion pretreatment at a temperature of 200 degrees C. (C) 2015 Elsevier Ltd. All rights reserved.
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11.
  • Borling, Jenny Maria, et al. (författare)
  • Combined moist airtight storage and feed fermentation of barley by the yeast Wickerhamomyces anomalus and a lactic acid bacteria consortium
  • 2015
  • Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • This study combined moist airtight storage of moist grain with pig feed fermentation. Starter cultures with the potential to facilitate both technologies were added to airtight stored moist crimped cereal grain, and the impact on storage microflora and the quality of feed fermentations generated from the grain was investigated. Four treatments were compared: three based on moist barley, either un-inoculated (M), inoculated with Wickerhamomyces anomalus (W), or inoculated with W anomalus and LAB starter culture, containing Pediococcus acidilactici DSM 16243, Pediococcus pentosaceus DSM 12834 and Lactobacillus plantarum DSM 12837 (WLAB); and one treatment based on dried barley (D). After 6 weeks of storage, four feed fermentations FM, FW, FWLAB, and FD, were initiated from M, W, WLAB, and D, respectively, by mixing the grain with water to a dry matter content of 30%. Each treatment was fermented in batch initially for 7 days and then kept in a continuous mode by adding new feed daily with 50% back-slop. During the 6 week storage period, the average water activity decreased in M, W and WLAB from 0.96 to 0.85, and cereal pH decreased from approximately 6.0 at harvest to 4.5. Feed fermentation conferred a further pH decrease to 3.8-4.1. In M, W and WLAB, molds and Enterobacteriaceae were mostly below detection limit, whereas both organism groups were detected in D. In fermented feed, Enterobacteriaceae were below detection limit in almost all conditions. Molds were detected in FD, for most of the fermentation time in FM and at some sampling points in FW and FWLAB. Starter organisms, especially W anomalus and L. plantarum comprised a considerable proportion of the yeast and LAB populations, respectively, in both stored grain and fermented feed. However, autochthonous Pichia kudriavzevii and Kazachstania exigua partially dominated the yeast populations in stored grain and fermented feed, respectively.
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12.
  • Brandenburg, Jule, et al. (författare)
  • Biochemical profiling, prediction of total lipid content and fatty acid profile in oleaginous yeasts by FTIR spectroscopy
  • 2019
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 12
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundOleaginous yeasts are considered as a potential lipid source for food, feed and biofuel production. In order to make the yeast-based lipid production environmentally and economically sustainable, there is a need for screening studies in order to find the best yeast lipid producers on different substrates, and to optimize cultivation conditions. Since the target parameter of such screening studies are lipid amounts and profiles, an analytical technique that is able to perform lipid analyses rapidly, reproducible and with high precision is highly desirable. The main objective of this study was to establish the non-invasive high-throughput Fourier transform infrared (FTIR) spectroscopy analysis for the prediction of lipid content and profile in oleaginous yeasts.ResultsHigh-throughput FTIR spectroscopy allowed characterizing the total biochemical profile of oleaginous yeasts and enabled us to identify strains and substrate(s) providing the highest total lipid content. Some of the yeast strains grown under nitrogen-limiting conditions with glucose/xylose/mixture of glucose and xylose as carbon sources were accumulating lipids with a high proportion of free fatty acids. FTIR spectra were used to predict gravimetric and gas chromatography data by establishing multivariate calibration models. Coefficients of determination (R-2) for calibration models were obtained in a range between 0.62 and 0.92 for predicting lipid content. When using an independent test set, R-2 values between 0.53 and 0.79 were achieved for predicting fatty acid profile. The best spectral region(s) for the prediction of total lipid content was 3100-2800cm(-1) combined with 1800-700cm(-1), and for prediction of summed saturated (SAT), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids: 3100-2800cm(-1), 3100-2800cm(-1) combined with 1700-1715cm(-1) and 3100-2800cm(-1) combined with 1800-1715cm(-1), respectively. The highest lipid accumulation was observed for strains Rhodotorula babjevae DBVPG 8058 on glucose and mixture of glucose and xylose and Lipomyces starkeyi CBS 2512 on xylose.ConclusionsApplying FTIR spectroscopy combined with multivariate data analysis allows performing rapid, non-invasive, reproducible and precise quantitative predictions of total lipid content and lipid profile. It allows also detecting different lipid fractions as triacylglycerols (TAGs) and free fatty acids and evaluating the total biochemical profile of cells. Several yeast strains with high lipid accumulation were identified.
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13.
  • Brandenburg, Jule, et al. (författare)
  • Bioethanol and lipid production from the enzymatic hydrolysate of wheat straw after furfural extraction
  • 2018
  • Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 102, s. 6269-6277
  • Tidskriftsartikel (refereegranskat)abstract
    • This study investigates biofuel production from wheat straw hydrolysate, from which furfural was extracted using a patented method developed at the Latvian State Institute of Wood Chemistry. The solid remainder after furfural extraction, corresponding to 67.6% of the wheat straw dry matter, contained 69.9% cellulose of which 4% was decomposed during the furfural extraction and 26.3% lignin. Enzymatic hydrolysis released 44% of the glucose monomers in the cellulose. The resulting hydrolysate contained mainly glucose and very little amount of acetic acid. Xylose was not detectable. Consequently, the undiluted hydrolysate did not inhibit growth of yeast strains belonging to Saccharomyces cerevisiae, Lipomyces starkeyi, and Rhodotorula babjevae. In the fermentations, average final ethanol concentrations of 23.85 g/l were obtained, corresponding to a yield of 0.53 g ethanol per g released glucose. L. starkeyi generated lipids with a rate of 0.08 g/h and a yield of 0.09 g per g consumed glucose. R. babjevae produced lipids with a rate of 0.18 g/h and a yield of 0.17 per g consumed glucose. In both yeasts, desaturation increased during cultivation. Remarkably, the R. babjevae strain used in this study produced considerable amounts of heptadecenoic, alpha,- and gamma-linolenic acid.
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14.
  • Brandenburg, Jule, et al. (författare)
  • Lipid production from hemicellulose with Lipomyces starkeyi in a pH regulated fed-batch cultivation
  • 2016
  • Ingår i: Yeast. - : Wiley. - 0749-503X. ; 33, s. 451-462
  • Tidskriftsartikel (refereegranskat)abstract
    • This study investigated lipid production from the hemicellulosic fraction of birch wood by the oleaginous yeast Lipomyces starkeyi. Birch wood chips were thermochemically pretreated by hot water extraction, and the liquid phase, containing 45.1 g/l xylose as the major sugar, 13.1 g/l acetic acid and 4.7 g/l furfural, was used for cultivations of L. starkeyi CBS1807. The hydrolysate strongly inhibited yeast growth; the strain could only grow in medium containing 30% hydrolysate at pH 6. At pH 5, growth stopped already upon the addition of about 10% hydrolysate. In fed-batch cultures fed with hydrolysate or a model xylose-acetic acid mixture, co-consumption of xylose and acetic acid was observed, which resulted in a pH increase. This phenomenon was utilized to establish a pH-stat fed-batch cultivation in which, after an initial feeding, hydrolysate or model mixture was connected to the pH-regulation system of the bioreactor. Under these conditions we obtained growth and lipid production in cultures grown on either xylose or glucose during the batch phase. In cultivations fed with model mixture, a maximum lipid content of 60.5% of the cell dry weight (CDW) was obtained; however, not all xylose was consumed. When feeding hydrolysate, growth was promoted and carbon sources were completely consumed, resulting in higher CDW with maximum lipid content of 51.3%. In both cultures the lipid concentration was 8 g/l and a lipid yield of 0.1 g/g carbon source was obtained. Lipid composition was similar in all cultivations, with C18:1 and C16:0 being the most abundant fatty acids. Copyright (c) 2016 John Wiley & Sons, Ltd.
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15.
  • Brandenburg, Jule, et al. (författare)
  • Oleaginous yeasts respond differently to carbon sources present in lignocellulose hydrolysate
  • 2021
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 14
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Microbial oils, generated from lignocellulosic material, have great potential as renewable and sustainable alternatives to fossil-based fuels and chemicals. By unravelling the diversity of lipid accumulation physiology in different oleaginous yeasts grown on the various carbon sources present in lignocellulose hydrolysate (LH), new targets for optimisation of lipid accumulation can be identified. Monitoring lipid formation over time is essential for understanding lipid accumulation physiology. This study investigated lipid accumulation in a variety of oleaginous ascomycetous and basidiomycetous strains grown in glucose and xylose and followed lipid formation kinetics of selected strains in wheat straw hydrolysate (WSH). Results Twenty-nine oleaginous yeast strains were tested for their ability to utilise glucose and xylose, the main sugars present in WSH. Evaluation of sugar consumption and lipid accumulation revealed marked differences in xylose utilisation capacity between the yeast strains, even between those belonging to the same species. Five different promising strains, belonging to the species Lipomyces starkeyi, Rhodotorula glutinis, Rhodotorula babjevae and Rhodotorula toruloides, were grown on undiluted wheat straw hydrolysate and lipid accumulation was followed over time, using Fourier transform-infrared (FTIR) spectroscopy. All five strains were able to grow on undiluted WSH and to accumulate lipids, but to different extents and with different productivities. R. babjevae DVBPG 8058 was the best-performing strain, accumulating 64.8% of cell dry weight (CDW) as lipids. It reached a culture density of 28 g/L CDW in batch cultivation, resulting in a lipid content of 18.1 g/L and yield of 0.24 g lipids per g carbon source. This strain formed lipids from the major carbon sources in hydrolysate, glucose, acetate and xylose. R. glutinis CBS 2367 also consumed these carbon sources, but when assimilating xylose it consumed intracellular lipids simultaneously. Rhodotorula strains contained a higher proportion of polyunsaturated fatty acids than the two tested Lipomyces starkeyi strains. Conclusions There is considerable metabolic diversity among oleaginous yeasts, even between closely related species and strains, especially when converting xylose to biomass and lipids. Monitoring the kinetics of lipid accumulation and identifying the molecular basis of this diversity are keys to selecting suitable strains for high lipid production from lignocellulose.
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16.
  • Chmielarz, Mikolaj, et al. (författare)
  • FT-NIR: a tool for rapid intracellular lipid quantification in oleaginous yeasts
  • 2019
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 12
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundLipid extraction for quantification of fat content in oleaginous yeasts often requires strong acids and harmful organic solvents; it is laborious and time-consuming. Therefore, in most cases just endpoint measurements of lipid accumulation are performed and kinetics of intracellular lipid accumulation is difficult to follow. To address this, we created a prediction model using Fourier-transform near-infrared (FT-NIR) spectroscopy. This method allows to measure lipid content in yeast.MethodsThe FT-NIR calibration sets were constructed from spectra of freeze-dried cells of the oleaginous yeasts Rhodotorula toruloides CBS 14, Lipomyces starkeyi CBS 1807 and Yarrowia lipolytica CBS 6114. The yeast cells were obtained from different cultivation conditions. Freeze-dried cell pellets were scanned using FT-NIR in the Multi Purpose Analyser (MPA) from Bruker. The obtained spectra were assigned corresponding to total fat content, obtained from lipid extraction using a modified Folch method. Quantification models using partial least squares (PLS) regression were built, and the calibration sets were validated on independently cultivated samples. The R. toruloides model was additionally tested on Rhodotorula babjevae DBVPG 8058 and Rhodotorula glutinis CBS 2387.ResultsThe R-2 of the FT-NIR model for R. toruloides was 98%, and the root mean square error of cross-validation (RMSECV) was 1.53. The model was validated using a separate set of R. toruloides samples with a root mean square error of prediction (RMSEP) of 3.21. The R-2 of the Lipomyces model was 96%, with RMSECV 2.4 and RMSEP 3.8. The R-2 of the mixed model, including all tested yeast strains, was 90.5%, with RMSECV 2.76 and RMSEP 3.22, respectively. The models were verified by predicting the total fat content in newly cultivated and freeze-dried samples. Additionally, the kinetics of lipid accumulation of a culture were followed and compared with standard lipid extraction methods.ConclusionsUsing FT-NIR spectroscopy, we have developed a faster, less laborious and non-destructive quantification of yeast intracellular lipid content compared to methods using lipid extraction.
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17.
  • Chmielarz, Mikolaj, et al. (författare)
  • Microbial lipid production from crude glycerol and hemicellulosic hydrolysate with oleaginous yeasts
  • 2021
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 14
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Crude glycerol (CG) and hemicellulose hydrolysate (HH) are low-value side-products of biodiesel transesterification and pulp-and paper industry or lignocellulosic ethanol production, respectively, which can be converted to microbial lipids by oleaginous yeasts. This study aimed to test the ability of oleaginous yeasts to utilise CG and HH and mixtures of them as carbon source. Results Eleven out of 27 tested strains of oleaginous yeast species were able to grow in plate tests on CG as sole carbon source. Among them, only one ascomycetous strain, belonging to Lipomyces starkeyi, was identified, the other 10 strains were Rhodotorula spec. When yeasts were cultivated in mixed CG/ HH medium, we observed an activation of glycerol conversion in the Rhodotorula strains, but not in L. starkeyi. Two strains-Rhodotorula toruloides CBS 14 and Rhodotorula glutinis CBS 3044 were further tested in controlled fermentations in bioreactors in different mixtures of CG and HH. The highest measured average biomass and lipid concentration were achieved with R. toruloides in 10% HH medium mixed with 55 g/L CG-19.4 g/L and 10.6 g/L, respectively, with a lipid yield of 0.25 g lipids per consumed g of carbon source. Fatty acid composition was similar to other R. toruloides strains and comparable to that of vegetable oils. Conclusions There were big strain differences in the ability to convert CG to lipids, as only few of the tested strains were able to grow. Lipid production rates and yields showed that mixing GC and HH have a stimulating effect on lipid accumulation in R. toruloides and R. glutinis resulting in shortened fermentation time to reach maximum lipid concentration, which provides a new perspective on converting these low-value compounds to microbial lipids.
  •  
18.
  • Dererie, Debebe Yilma, et al. (författare)
  • Improved bio-energy yields via sequential ethanol fermentation and biogas digestion of steam exploded oat straw
  • 2011
  • Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 102:6, s. 4449-4455
  • Tidskriftsartikel (refereegranskat)abstract
    • Using standard laboratory equipment, thermochemically pretreated oat straw was enzymatically saccharified and fermented to ethanol, and after removal of ethanol the remaining material was subjected to biogas digestion. A detailed mass balance calculation shows that, for steam explosion pretreatment, this combined ethanol fermentation and biogas digestion converts 85-87% of the higher heating value (HHV) of holocellulose (cellulose and hemicellulose) in the oat straw into biofuel energy. The energy (HHV) yield of the produced ethanol and methane was 9.5-9.8 MJ/(kg dry oat straw), which is 28-34% higher than direct biogas digestion that yielded 7.3-7.4 MJ/(kg dry oat straw). The rate of biogas formation from the fermentation residues was also higher than from the corresponding pretreated but unfermented oat straw, indicating that the biogas digestion could be terminated after only 24 days. This suggests that the ethanol process acts as an additional pretreatment for the biogas process.
  •  
19.
  • Druvefors, Ulrika Ädel, et al. (författare)
  • Nutrient effects on biocontrol of Penicillium roqueforti by Pichia anomala J121 during airtight storage of wheat
  • 2005
  • Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 71:4, s. 1865-1869
  • Tidskriftsartikel (refereegranskat)abstract
    • The biocontrol yeast Pichia anomala inhibits the growth of a variety of mold species. We examined the mechanism underlying the inhibition of the grain spoilage mold Penicillium roqueforti by the biocontrol yeast P. anomala J121 during airtight storage. The biocontrol effect in a model grain silo with moist wheat (water activity of 0.96) was enhanced when complex medium, maltose, or glucose was added. Supplementation with additional nitrogen or vitamin sources did not affect the biocontrol activity of the yeast. The addition of complex medium or glucose did not significantly influence the yeast cell numbers in the silos, whether in the presence or absence of P. roqueforti. Mold growth was not influenced by the addition of nutrients, if cultivated without yeast. The products of glucose metabolism, mainly ethanol and ethyl acetate, increased after glucose addition to P. anomala-inoculated treatments. Our results suggest that neither competition for nutrients nor production of a glucose-repressible cell wall lytic enzyme is the main mode of action of biocontrol by P. anomala in this grain system. Instead, the mold-inhibiting effect probably is due to the antifungal action of metabolites, most likely a combination of ethyl acetate and ethanol, derived from glycolysis. The discovery that sugar amendments enhance the biocontrol effect of P. anomala suggests novel ways of formulating biocontrol yeasts.
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20.
  • Fredlund, Elisabeth, et al. (författare)
  • Influence of ethyl acetate production and ploidy on the anti-mould activity of Pichia anomala
  • 2004
  • Ingår i: FEMS Microbiology Letters. - : Elsevier. - 0378-1097 .- 1574-6968. ; 238:1, s. 133-137
  • Tidskriftsartikel (refereegranskat)abstract
    • A diploid and a haploid strain of Pichia anomala were tested for their biocontrol ability against the spoilage mould Penicillium roqueforti in glass tubes filled with grain at two water activities (a(w)). At a(w) 0.98, the two yeast strains grew and inhibited mould growth equally well and showed similar patterns of ethyl acetate production, reaching maximum values of 10-14 mug ml(-1) headspace. At a(w) 0.95, both growth and biocontrol performance of the haploid strain were reduced. Ethyl acetate formation was also substantially reduced, with maximum headspace concentrations of 4 mug ml(-1). We conclude that ethyl acetate is a major component of the anti-mould activity. The inhibitory effect of ethyl acetate was confirmed in a bioassay where the pure compound reduced biomass production of P. roqueforti.
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21.
  • Fredlund, Elisabeth, et al. (författare)
  • Oxygen and carbon source-regulated expression of PDC and ADH genes in the respiratory yeast Pichia anomala
  • 2006
  • Ingår i: Yeast. - West Sussex, USA : John Wiley & Sons. - 0749-503X .- 1097-0061. ; 23:16, s. 1137-1149
  • Tidskriftsartikel (refereegranskat)abstract
    • We amplified, sequenced and studied the transcriptional regulation of genes of the alcoholic fermentation pathway in the biocontrol and non-Saccharomyces wine yeast, Pichia anomala. Two ADH isogenes, PaADH1 and PaADH2, and one PDC gene, PaPDC1, were amplified from genomic P. anomala DNA by a two-step PCR approach, using degenerated primers against conserved regions of the respective genes for cloning core regions, and PCR-based gene walking for cloning the respective 5' and 3'-ends. According to sequence analysis, ADHI and PDC1 are most likely cytoplasmatic proteins, while ADH2 is most probably localized in the mitochondria. PaADH1 was expressed during aerobic growth on glucose, ethanol and succinate, but was ninefold upregulated in response to oxygen limitation when grown on glucose. The gene seems to be involved in both production and consumption of ethanol. Only low expression of PaADH2 was detected during growth on glucose and ethanol, but it was highly expressed during growth on the non-fermentable carbon source succinate and repressed by the addition of glucose. PaPDC1 was expressed during aerobic growth on glucose and was upregulated four-fold in response to oxygen limitation. PaPDC1 expression was lower in cells grown on ethanol and succinate than on glucose and was up- regulated two- and four-fold, respectively, after glucose addition. Our results demonstrate that transcription of genes of the fermentative pathway is regulated by hypoxia and carbon source but posttranscriptional regulation may play a major role in regulating the metabolic flux.
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22.
  • Fredlund, Elisabeth, et al. (författare)
  • Oxygen- and glucose-dependent regulation of central carbon metabolism in Pichia anomala
  • 2004
  • Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 70:10, s. 5905-5911
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated the regulation of the central aerobic and hypoxic metabolism of the biocontrol and non-Saccharomyces wine yeast Pichia anomala. In aerobic batch culture, P. anomala grows in the respiratory mode with a high biomass yield (0.59 g [dry weight] of cells g of glucose(-1)) and marginal ethanol, glycerol, acetate, and ethyl acetate production. Oxygen limitation, but not glucose pulse, induced fermentation with substantial ethanol production and 10-fold-increased ethyl acetate production. Despite low or absent ethanol formation, the activities of pyruvate decarboxylase and alcohol dehydrogenase were high during aerobic growth on glucose or succinate. No activation of these enzyme activities was observed after a glucose pulse. However, after the shift to oxygen limitation, both enzymes were activated threefold. Metabolic flux analysis revealed that the tricarboxylic acid pathway operates as a cycle during aerobic batch culture and as a two-branched pathway under oxygen limitation. Glucose catabolism through the pentose phosphate pathway was lower during oxygen limitation than under aerobic growth. Overall, our results demonstrate that P. anomala exhibits a Pasteur effect and not a Crabtree effect, i.e., oxygen availability, but not glucose concentration, is the main stimulus for the regulation of the central carbon metabolism.
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23.
  • Fredlund, Elisabeth, et al. (författare)
  • The correlation of oxygen and sugar dependent regulation of glycolysis to the biocontrol activity of the yeast Pichia anomala
  • 2003
  • Ingår i: Yeast. - : John Wiley & Sons. - 0749-503X .- 1097-0061. ; 20, s. S352-S352
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Pichia anomala inhibits growth of mould during airtight storage of moist cereal grain for animal feed. The cereal grain is stored in large airtight containers where the anaerobic environment prevents growth of mould. Air can leak into the system due to the removal of grain or technical difficulties in keeping completely anaerobic conditions. This subsequently enables growth of spoilage moulds. Addition of P. anomala cells inhibits the growth of mould making the system more robust [1]. We analysed the physiological basis of the biocontrol activity. P. anomala is a Crabtree negative yeast but in contrast to other Crabtree negative organisms it can grow under anaerobic conditions [2]. The ability to switch between respiratory and fermentative growth in response to O2-availability is essential for its survival in the airtight system and for its biocontrol activity. End products of the sugar metabolism had inhibitory effects on mould growth. Addition of glucose to a model biocontrol system enhanced biocontrol activity without increasing yeast biomass, suggesting the involvement of a product of glycolysis in biocontrol. Sugar consumption, production of ethanol and other metabolites and the activity of key enzymes were investigated in cells grown under defined conditions of oxygen and nutrient supply. The impact of the different parameters on biocontrol activity is discussed. [1] Druvefors et al. (2002) FEMS Yeast Res. 2: 389-394 [2] Fredlund et al. (2002) FEMS Yeast Res. 2: 395-402
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24.
  • Görgens, Johann F, et al. (författare)
  • Amino acid supplementation, controlled oxygen limitation and sequential double induction improves heterologous xylanase production by Pichia stipitis
  • 2005
  • Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1364 .- 1567-1356. ; 5:6-7, s. 677-683
  • Tidskriftsartikel (refereegranskat)abstract
    • Heterologous endo-beta-1,4-xylanase was produced by Pichia stipitis under control of the hypoxia-inducible PsADH2-promoter in a high-cell-clensity culture. After promoter induction by a shift to oxygen limitation, different aeration rates (oxygen transfer rates) were applied while maintaining oxygen-limitation. Initially, enzyme production was higher in oxygen-limited cultures with high rates of oxygen transfer, although the maximum xylanase activity was not significantly influenced. Amino acid supplementation increased the production of the heterologous endo-beta-1,4-xylanase significantly in highly aerated oxygen-limited cultures, until glucose was depleted. A slight second induction of the promoter was observed in all cultures after the glucose had been consumed. The second induction was most obvious in amino acid-supplemented cultures with higher oxygen transfer rates during oxygen limitation. When such oxygen-limited cultures were shifted back to fully aerobic conditions, a significant re-induction of heterologous endo-beta-1,4-xylanase production was observed. Re-induction was accompanied by ethanol consumption. A similar protein production pattern was observed when cultures were first grown on ethanol as sole carbon source and subsequently glucose and oxygen limitation were applied. Thus, we present the first expression system in yeast with a sequential double-inducible promoter. (c) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.
  •  
25.
  • Haddad Momeni, Majid, et al. (författare)
  • Improved bio-energy yields via sequential ethanol fermentation and biogas digestion of steam exploded oat straw
  • 2011
  • Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 102, s. 4449-4455
  • Tidskriftsartikel (refereegranskat)abstract
    • Using standard laboratory equipment, thermochemically pretreated oat straw was enzymatically saccharified and fermented to ethanol, and after removal of ethanol the remaining material was subjected to biogas digestion. A detailed mass balance calculation shows that, for steam explosion pretreatment, this combined ethanol fermentation and biogas digestion converts 85-87% of the higher heating value (HHV) of holocellulose (cellulose and hemicellulose) in the oat straw into biofuel energy. The energy (HHV) yield of the produced ethanol and methane was 9.5-9.8 MJ/(kg dry oat straw), which is 28-34% higher than direct biogas digestion that yielded 7.3-7.4 MJ/(kg dry oat straw). The rate of biogas formation from the fermentation residues was also higher than from the corresponding pretreated but unfermented oat straw, indicating that the biogas digestion could be terminated after only 24 days. This suggests that the ethanol process acts as an additional pretreatment for the biogas process. (C) 2010 Elsevier Ltd. All rights reserved.
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26.
  • Huyben, David, et al. (författare)
  • Effects of dietary inclusion of the yeasts Saccharomyces cerevisiae and Wickerhamomyces anomalus on gut microbiota of rainbow trout
  • 2017
  • Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 473, s. 528-537
  • Tidskriftsartikel (refereegranskat)abstract
    • Rainbow trout (Oncorhynchus mykiss) were fed for 10 weeks on a diet containing either 30% fish meal (FM) or with 20, 40 and 60% replacement of fish meal protein with Saccharomyces cerevisiae (SC) or a mixture of Wickerhamomyces anomalus and S. cerevisiae(WA). Luminal contents and mucosal tissue from the distal intestine were collected and analysed for yeast and bacterial loads by agar plating. Diversity and abundance were determined by sequencing of amplicons generated from the 26S rRNA (yeast) and 16S rRNA (bacteria) genes. In addition, the diets were analysed before and after feed extrusion to determine the viability and composition of the yeasts ingested by the fish. After extrusion, 9-10 log cells g(-1) of yeast were still intact in the SC and WA diets, but culturable yeast showed log-reductions of 5-7 CFU g(-1). For yeasts isolated from the gut contents, 81-96% of colonies consisted of Debaryomyces hansenii, with few or no colonies of S. cerevisiae or W. anomalus despite their high inclusion rate in the diets. Characterisation of gut bacteria using Illumina MiSeq showed that 70 and 19% of sequences were classified to the phyla Firmicutes and Proteobacteria, specifically sequences identified as Leuconostocaceae, Lactobacillaceae and Photobacterium. Compared with the FM diet, the WA40 diet reduced bacterial diversity, whereas the WA60 diet increased the abundance of the pathogenic yeast Candida albicans and reduced lactic acid bacteria in the gut. Overall, 40 and 60% replacement of fish meal protein with a mixture of W. anomalus and S. cerevisiae significantly altered the gut microbiota of rainbow trout, while 20% replacement and diets with only S. cerevisiae had little or no effect. (C) 2017 Elsevier B.V. All rights reserved.
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27.
  • Huyben, David, et al. (författare)
  • Effects of feeding yeasts, Saccharomyces cerevisiae and Wickerhamomyces anomalus, on gut microbiota of rainbow trout
  • 2016
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Introduction  Single cell proteins, such as yeasts, are an ideal feed alternative to plant and fish meals as they do not compete as food for humans. Previous studies have fed live yeast, such asSaccharomyces cerevisiae, in cold pelleted diets to farmed fish in order to increase beneficial microbiota in the gut (Gatesoupe, 2007). However, commercial salmonid diets are typically extruded at high temperatures, which can inactivate yeasts and reduce their effects on gut microbiota. In addition, previous studies have used culture-based methods to determine gut microbiota, while the development of next generation sequencing has improved identification of unculturable microbiota. The objective of this study was to determine the effect of feeding yeasts,S. cerevisiae and Wickerhamomyces anomalus, on microbiota in the distal intestine of rainbow trout (Oncorhynchus mykiss).  Materials and methods  A diet of fish meal (FM) was used as a control against yeast diets that replaced 20, 40 and 60% of fish meal (digestible protein basis) with either S. cerevisiae(SC) orW.anomalus/S. cerevisiaemix (WA; Jästbolaget AB, Sweden). Diets were extruded at 120-130oC and later fed to triplicate tanks of 35 rainbow trout for 10 weeks. Afterwards, content and mucosa from the distal intestine of 3 fish per tank were collected. Ingredients, diets and gut samples were plated on yeast-peptone-D-glucose, then 26S rDNA were PCR-amplified and sequenced to determine live yeast counts and taxa. Diets and yeast ingredients were further examined microscopically to determine cell counts of yeast. For gut bacteria, 16S rDNA were PCR-amplified, barcoded and next generation sequenced using Illumina platform (SciLifeLab AB, Sweden). Significant differences (p<0.05) between diets were determined using ANOVA and ANOSIM methods.  Results  The yeast ingredients,S. cerevisiaeor W. anomalus/S. cerevisiae mix, contained between 9-10 log cfu g-1and SC and WA diets contained 7-8 log cfu g-1before extrusion. After extrusion, all diets had over 4-log reduction in cfu g-1(cultured yeast), however 7-8 log cells g-1of yeast were still viable. Diets of SC and WA contained between 96-100%S. cerevisiaeand 0-20%W. anomalus.After 10 weeks of feeding, the distal intestine contained between 84-96 Þbaryomyces hanseniiwith few colonies of S. cerevisiae and noW. anomalus. For bacteria, the distal intestine contained between 37-62 % ofLeuconostocaceae,Lactobacillaceae and Photobacteriumand significant differences in taxa abundance and similarity were found between fish fed SC60, WA40 and WA60 compared with the FM diet (Fig. 1). Discussion and conclusion This study is the first to analyse intestinal microbiota of rainbow trout fed yeast diets using next generation sequencing. In addition, few studies have investigated the viability and log reduction of yeast after feed extrusion. The low level of culturable yeast compared with the high level of intact yeast cells found after diet extrusion suggested that high temperature from extrusion inactivated yeasts, but did not disrupt the cells. Inactivated, non-disrupted yeast is not ideal because the yeast cannot cultivate the intestine or release nutrients for metabolic uptake. The lack of S. cerevisiaeandW. anomalusin the distal intestine despite the high level of yeast ingestion, suggests that large amounts of yeast were metabolised. However, higher levels of unculturable yeast cells may have been present in the intestinal content and mucosa. For gut bacteria, most were Lactic Acid Bacteria (Lactobacillales order), which includesCarnobacteriaceae, Leuconstocaceae, Leuconstocaceaeand Streptococcaceae families. In comparison, Ingerslev et al. (2014) found similar levels ofStreptococcus, Leuconostoc,Enterobacteriaceae and Lactobacillusin rainbow trout fed fish and plant-based diets.Significant differences in bacteria abundance for fish fed SC60, WA40 and WA60 diets indicated thatW. anomalushad a higher effect thanS. cerevisiaeand that more than 20% replacement of fish meal with yeast affected gut microbiota in rainbow trout.  References  Gatesoupe F.J. 2007. Live yeasts in the gut: Natural occurrence, dietary introduction, and their effects on fish health and development. Aquaculture 267: 20-30. Ingerslev H.C., L. von Gersdorff Jørgensen, M. Lenz Strube, N. Larsen, I. Dalsgaard, M. Boye, and L. Madsen. 2014. The development of the gut microbiota in rainbow trout (Oncorhynchus mykiss) is affected by first feeding and diet type. Aquaculture 424-425: 24-34.
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28.
  • Huyben, David, et al. (författare)
  • Screening of intact yeasts and cell extracts to reduce Scrapie prions during biotransformation of food waste
  • 2018
  • Ingår i: Acta Veterinaria Scandinavica. - : Springer Science and Business Media LLC. - 1751-0147. ; 60
  • Tidskriftsartikel (refereegranskat)abstract
    • Yeasts can be used to convert organic food wastes to protein-rich animal feed in order to recapture nutrients. However, the reuse of animal-derived waste poses a risk for the transmission of infectious prions that can cause neurodegeneration and fatality in humans and animals. The aim of this study was to investigate the ability of yeasts to reduce prion activity during the biotransformation of waste substrates-thereby becoming a biosafety hurdle in such a circular food system. During pre-screening, 30 yeast isolates were spiked with Classical Scrapie prions and incubated for 72 h in casein substrate, as a waste substitute. Based on reduced Scrapie seeding activity, waste biotransformation and protease activities, intact cells and cell extracts of 10 yeasts were further tested. Prion analysis showed that five yeast species reduced Scrapie seeding activity by approximately 1 log10 or 90%. Cryptococcus laurentii showed the most potential to reduce prion activity since both intact and extracted cells reduced Scrapie by 1 log10 and achieved the highest protease activity. These results show that select forms of yeast can act as a prion hurdle during the biotransformation of waste. However, the limited ability of yeasts to reduce prion activity warrants caution as a sole barrier to transmission as higher log reductions are needed before using waste-cultured yeast in circular food systems.
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29.
  • Karlsson Potter, Hanna, et al. (författare)
  • A systems analysis of biodiesel production from wheat straw using oleaginous yeast : process design, mass and energy balances
  • 2016
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 9:1, s. 1-13
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Biodiesel is the main liquid biofuel in the EU and is currently mainly produced from vegetable oils. Alternative feedstocks are lignocellulosic materials, which provide several benefits compared with many existing feedstocks. This study examined a technical process and its mass and energy balances to gain a systems perspective of combined biodiesel (FAME) and biogas production from straw using oleaginous yeasts. Important process parameters with a determining impact on overall mass and energy balances were identified and evaluated. Results: In the base case, 41% of energy in the biomass was converted to energy products, primary fossil fuel use was 0.37 MJprim/MJ produced and 5.74 MJ fossil fuels could be replaced per kg straw dry matter. The electricity and heat produced from burning the lignin were sufficient for process demands except in scenarios where the yeast was dried for lipid extraction. Using the residual yeast cell mass for biogas production greatly increased the energy yield, with biogas contributing 38% of total energy products. Conclusions: In extraction methods without drying the yeast, increasing lipid yield and decreasing the residence time for lipid accumulation are important for the energy and mass balance. Changing the lipid extraction method from wet to dry makes the greatest change to the mass and energy balance. Bioreactor agitation and aeration for lipid accumulation and yeast propagation is energy demanding. Changes in sugar concentration in the hydrolysate and residence times for lipid accumulation greatly affect electricity demand, but have relatively small impacts on fossil energy use (NER) and energy yield (EE). The impact would probably be greater if externally produced electricity were used.
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30.
  • Karlsson Potter, Hanna, et al. (författare)
  • Greenhouse gas performance of biochemical biodiesel production from straw : Soil organic carbon changes and time-dependent climate impact
  • 2017
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 10:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Use of bio-based diesel is increasing in Europe. It is currently produced from oilseed crops, but can also be generated from lignocellulosic biomass such as straw. However, removing straw affects soil organic carbon (SOC), with potential consequences for the climate impact of the biofuel. This study assessed the climate impacts and energy balance of biodiesel production from straw using oleaginous yeast, with subsequent biogas production from the residues, with particular emphasis on SOC changes over time. It also explored the impact of four different scenarios for returning the lignin fraction of the biomass to soil to mitigate SOC changes. Climate impact was assessed using two methods, global warming potential (GWP) and a time-dependent temperature model (ΔT s ) that describes changes in mean global surface temperature as a function of time or absolute temperature change potential (AGTP). Results: Straw-derived biodiesel reduced GWP by 33-80% compared with fossil fuels and primary fossil energy use for biodiesel production was 0.33-0.80 MJprim/MJ, depending on the scenario studied. Simulations using the time-dependent temperature model showed that a scenario where all straw fractions were converted to energy carriers and no lignin was returned to soil resulted in the highest avoided climate impact. The SOC changes due to straw removal had a large impact on the results, both when using GWP and the time-dependent temperature model. Conclusions: In a climate perspective, it is preferable to combust straw lignin to produce electricity rather than returning it to the soil if the excess electricity replaces natural gas electricity, according to results from both GWP and time-dependent temperature modelling. Using different methods to assess climate impact did not change the ranking between the scenarios, but the time-dependent temperature model provided information about system behaviour over time that can be important for evaluation of biofuel systems, particularly in relation to climate target deadlines.
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31.
  • Martín Hernández, Giselle De La Caridad, et al. (författare)
  • Chromosome-level genome assembly and transcriptome-based annotation of the oleaginous yeast Rhodotorula toruloides CBS 14
  • 2021
  • Ingår i: Genomics. - : Elsevier BV. - 0888-7543 .- 1089-8646. ; 113, s. 4022-4027
  • Tidskriftsartikel (refereegranskat)abstract
    • Rhodotorula toruloides is an oleaginous yeast with high biotechnological potential. In order to understand the molecular physiology of lipid synthesis in R. toruloides and to advance metabolic engineering, a high-resolution genome is required. We constructed a genome draft of R. toruloides CBS 14, using a hybrid assembly approach, consisting of short and long reads generated by Illumina and Nanopore sequencing, respectively. The genome draft consists of 23 contigs and 3 scaffolds, with a N50 length of 1,529,952 bp, thus largely representing chromosomal organization. The total size of the genome is 20,534,857 bp and the overall GC content is 61.83%. Transcriptomic data from different growth conditions was used to aid species-specific gene annotation. We annotated 9464 genes and identified 11,691 transcripts. Furthermore, we demonstrated the presence of a potential plasmid, an extrachromosomal circular structure of about 11 kb with a copy number about three times as high as the other chromosomes.
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32.
  • Martín Hernández, Giselle De La Caridad, et al. (författare)
  • Enhanced glycerol assimilation and lipid production in Rhodotorula toruloides CBS14 upon addition of hemicellulose primarily correlates with early transcription of energy-metabolism-related genes
  • 2023
  • Ingår i: Biotechnology for Biofuels and Bioproducts. - : Springer Science and Business Media LLC. - 2731-3654. ; 16
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundLipid formation from glycerol was previously found to be activated in Rhodotorula toruloides when the yeast was cultivated in a mixture of crude glycerol (CG) and hemicellulose hydrolysate (CGHH) compared to CG as the only carbon source. RNA samples from R. toruloides CBS14 cell cultures grown on either CG or CGHH were collected at different timepoints of cultivation, and a differential gene expression analysis was performed between cells grown at a similar physiological situation.ResultsWe observed enhanced transcription of genes involved in oxidative phosphorylation and enzymes localized in mitochondria in CGHH compared to CG. Genes involved in protein turnover, including those encoding ribosomal proteins, translation elongation factors, and genes involved in building the proteasome also showed an enhanced transcription in CGHH compared to CG. At 10 h cultivation, another group of activated genes in CGHH was involved in beta-oxidation, handling oxidative stress and degradation of xylose and aromatic compounds. Potential bypasses of the standard GUT1 and GUT2-glycerol assimilation pathway were also expressed and upregulated in CGHH 10 h. When the additional carbon sources from HH were completely consumed, at CGHH 36 h, their transcription decreased and NAD(+)-dependent glycerol-3-phosphate dehydrogenase was upregulated compared to CG 60 h, generating NADH instead of NADPH with glycerol catabolism. TPI1 was upregulated in CGHH compared to cells grown on CG in all physiological situations, potentially channeling the DHAP formed through glycerol catabolism into glycolysis. The highest number of upregulated genes encoding glycolytic enzymes was found after 36 h in CGHH, when all additional carbon sources were already consumed.ConclusionsWe suspect that the physiological reason for the accelerated glycerol assimilation and faster lipid production, was primarily the activation of enzymes that provide energy.
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33.
  • Martín Hernández, Giselle De La Caridad, et al. (författare)
  • Near Chromosome-Level Genome Assembly and Annotation of Rhodotorula babjevae Strains Reveals High Intraspecific Divergence
  • 2022
  • Ingår i: Journal of Fungi. - : MDPI AG. - 2309-608X. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • The genus Rhodotorula includes basidiomycetous oleaginous yeast species. Rhodotorula babjevae can produce compounds of biotechnological interest such as lipids, carotenoids, and biosurfactants from low value substrates such as lignocellulose hydrolysate. High-quality genome assemblies are needed to develop genetic tools and to understand fungal evolution and genetics. Here, we combined short- and long-read sequencing to resolve the genomes of two R. babjevae strains, CBS 7808 (type strain) and DBVPG 8058, at chromosomal level. Both genomes are 21 Mbp in size and have a GC content of 68.2%. Allele frequency analysis indicates that both strains are tetraploid. The genomes consist of a maximum of 21 chromosomes with a size of 0.4 to 2.4 Mbp. In both assemblies, the mitochondrial genome was recovered in a single contig, that shared 97% pairwise identity. Pairwise identity between most chromosomes ranges from 82 to 87%. We also found indications for strain-specific extrachromosomal endogenous DNA. A total of 7591 and 7481 protein-coding genes were annotated in CBS 7808 and DBVPG 8058, respectively. CBS 7808 accumulated a higher number of tandem duplications than DBVPG 8058. We identified large translocation events between putative chromosomes. Genome divergence values between the two strains indicate that they may belong to different species.
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34.
  • Mogodiniyai Kasmaei, Kamyar, et al. (författare)
  • A new in vitro ensiling technique for silage research
  • 2015
  • Ingår i: Anais do Simpósio Internacional sobre Qualidade e Conservação de Forragens. - 2175-4624. ; , s. 104-105
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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35.
  • Mogodiniyai Kasmaei, Kamyar, et al. (författare)
  • A new sterilization and inoculation method in silage research
  • 2015
  • Ingår i: Grass and Forage Science. - : Wiley. - 0142-5242 .- 1365-2494. ; 70, s. 668-673
  • Tidskriftsartikel (refereegranskat)abstract
    • The study aimed at evaluating an effective sterilization-inoculation technique to facilitate silage research on the effect of forage microflora on fermentation variables. The sterilization effect of heating at 60 degrees C for 3h+103 degrees C for 15h was tested on samples of grass, grass-clover, white clover and maize, pre-dried at 60 degrees C to a dry-matter (DM) content >900gkg(-1). The ensilability of treated samples, reconstituted to original DM concentration (250-390gkg(-1)), was assessed by inoculation with microfloras extracted from the original samples. Microfloral inoculants were obtained by a combination of centrifugation (15500g for 40min) and filtration (045 and 022m pore sizes) of the supernatant. The sterilization treatment effectively sterilized the forage samples but decreased water soluble carbohydrates by 49% and N buffer solubility by 22% and increased the acid detergent insoluble N proportion of total N by 53% (P<005). The reconstituted silages had 18% less lactic acid, 20% less ethanol and 37% less ammonia-N (P<005), but volatile fatty acids and 2,3-butanediol did not differ from the untreated silages (P>005). Counts of lactic acid bacteria, enterobacteria, clostridia, yeasts and moulds in the two silage treatments were also similar (P>005). It is concluded that, despite causing chemical and physical alterations, the sterilization-inoculation technique evaluated could be a useful tool for future studies on the effects of microflora on ensiling results.
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36.
  • Mogodiniyai Kasmaei, Kamyar, et al. (författare)
  • Ecology of silage microorganisms
  • 2014
  • Ingår i: Proceedings of the 5th Nordic Feed Science Conference, Uppsala, Sweden. ; :290, s. 5-9
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
  •  
37.
  • Müller, Bettina, et al. (författare)
  • Production of short-chain fatty acids (SCFAs) as chemicals or substrates for microbes to obtain biochemicals
  • 2023
  • Ingår i: Biotechnology for Biofuels and Bioproducts. - 2731-3654. ; 16
  • Forskningsöversikt (refereegranskat)abstract
    • Carboxylic acids have become interesting platform molecules in the last years due to their versatility to act as carbon sources for different microorganisms or as precursors for the chemical industry. Among carboxylic acids, short-chain fatty acids (SCFAs) such as acetic, propionic, butyric, valeric, and caproic acids can be biotechnologically produced in an anaerobic fermentation process from lignocellulose or other organic wastes of agricultural, industrial, or municipal origin. The biosynthesis of SCFAs is advantageous compared to chemical synthesis, since the latter relies on fossil-derived raw materials, expensive and toxic catalysts and harsh process conditions. This review article gives an overview on biosynthesis of SCFAs from complex waste products. Different applications of SCFAs are explored and how these acids can be considered as a source of bioproducts, aiming at the development of a circular economy. The use of SCFAs as platform molecules requires adequate concentration and separation processes that are also addressed in this review. Various microorganisms such as bacteria or oleaginous yeasts can efficiently use SCFA mixtures derived from anaerobic fermentation, an attribute that can be exploited in microbial electrolytic cells or to produce biopolymers such as microbial oils or polyhydroxyalkanoates. Promising technologies for the microbial conversion of SCFAs into bioproducts are outlined with recent examples, highlighting SCFAs as interesting platform molecules for the development of future bioeconomy.
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38.
  • Nagavara Nagaraj, Yashaswini, et al. (författare)
  • Identification, Quantification and Kinetic Study of Carotenoids and Lipids in Rhodotorula toruloides CBS 14 Cultivated on Wheat Straw Hydrolysate
  • 2022
  • Ingår i: Fermentation. - : MDPI AG. - 2311-5637. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • Production of carotenoids and lipids by Rhodotorula toruloides CBS 14 cultivated on wheat straw hydrolysate was investigated. An ultra-high-performance liquid chromatography (UHPLC) method for carotenoid quantification was developed and validated. Saponification effects on individual carotenoid quantification were identified, and lipid and carotenoid kinetics during cultivation were determined. The carotenoids beta-carotene, gamma-carotene, torularhodin, and torulene were identified; beta-carotene was the major carotenoid, reaching a maximum of 1.48 mg/100 g dry weight. Recoveries of the carotenoids were between 66% and 76%, except torulene and torularhodin, which had lower recoveries due to saponification effects. Total carotenoid content in saponified and unsaponified yeast extract, respectively, determined by UHPLC or photometer, respectively, was 1.99 mg/100 g and 4.02 mg beta-EQ/100 g dry weight. Growth kinetics showed a positive correlation between carotenoid content and lipid accumulation. beta-carotene was the major carotenoid at all time points. At the end of the cultivation, triacylglycerols (TAGs) were the major lipid class, with 58.1% +/- 3.32% of total lipids. There was also a high proportion of free fatty acids, reaching from 20.5% to 41.8% of total lipids. Oleic acid (C18:1) was the major fatty acid. The lipid yield at the end of the cultivation was 0.13 g/g of sugar consumed.
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39.
  • Olsen, Remi-Andre, et al. (författare)
  • De novo assembly of Dekkera bruxellensis : a multi technology approach using short and long-read sequencing and optical mapping
  • 2015
  • Ingår i: GigaScience. - : Oxford University Press (OUP). - 2047-217X. ; 4
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: It remains a challenge to perform de novo assembly using next-generation sequencing (NGS). Despite the availability of multiple sequencing technologies and tools (e.g., assemblers) it is still difficult to assemble new genomes at chromosome resolution (i.e., one sequence per chromosome). Obtaining high quality draft assemblies is extremely important in the case of yeast genomes to better characterise major events in their evolutionary history. The aim of this work is two-fold: on the one hand we want to show how combining different and somewhat complementary technologies is key to improving assembly quality and correctness, and on the other hand we present a de novo assembly pipeline we believe to be beneficial to core facility bioinformaticians. To demonstrate both the effectiveness of combining technologies and the simplicity of the pipeline, here we present the results obtained using the Dekkera bruxellensis genome. Methods: In this work we used short-read Illumina data and long-read PacBio data combined with the extreme long-range information from OpGen optical maps in the task of de novo genome assembly and finishing. Moreover, we developed NouGAT, a semi-automated pipeline for read-preprocessing, de novo assembly and assembly evaluation, which was instrumental for this work. Results: We obtained a high quality draft assembly of a yeast genome, resolved on a chromosomal level. Furthermore, this assembly was corrected for mis-assembly errors as demonstrated by resolving a large collapsed repeat and by receiving higher scores by assembly evaluation tools. With the inclusion of PacBio data we were able to fill about 5 % of the optical mapped genome not covered by the Illumina data.
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40.
  • Olstorpe, Matilda, et al. (författare)
  • Controlling fungal growth and mycotoxins in animal feed
  • 2011
  • Ingår i: Protective cultures, antimicrobial metabolites and bacteriophages for food and beverage biopreservation. - : Elsevier. - 9781845696696 ; :201, s. 225-239
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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41.
  • Olstorpe, Matilda, et al. (författare)
  • Effect of starter culture inoculation on feed hygiene and microbial population development in fermented pig feed composed of a cereal grain mix with wet wheat distillers' grain
  • 2010
  • Ingår i: Journal of Applied Microbiology. - Malden, USA : Wiley-Blackwell Publishing Inc.. - 1364-5072 .- 1365-2672. ; 108:1, s. 129-138
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: Investigating the influence of an added starter culture on the properties of fermented liquid pig feed.Methods and Results: Diets of cereal grain blended with wet wheat distillers' grain that were either not inoculated (WWDG), inoculated with a silage starter culture at start (WWDGsc1) or at start and at each backslopping (replacement of 80% the content with fresh mixture, simulating feed outtake, WWDGsc5) were fermented for 5 days, followed by 5 days of daily backslopping. Numbers of undesirable micro-organisms (enterobacteria, moulds) were reduced in all fermentations; particularly enterobacteria in the starter culture inoculated diets. Lactobacillus plantarum present in the starter culture became dominant in diets WWDGsc1 and WWDGsc5. However, Lactobacillus panis that was dominating WWDG was also abundant in WWDGsc1 and WWDGsc5. Yeast populations were not influenced by the starter culture, with Pichia fermentans dominating all fermentations. All diets had similar chemical characteristics with the exception of a significant increase of all tested organic acids in WWDGsc5.Conclusions: The addition of a starter culture influences the bacterial population in fermented liquid feed, but there is also a strong impact of the flora already present in the feed ingredients. The yeast population is not influenced by adding a lactic acid bacteria (LAB) starter culture. A consortium of LAB and yeast strains adapted to the fermentation should be used as starter culture.Significance and Impact of the Study: The results suggest that it is possible to influence the current unpredictable and spontaneous process of feed fermentation when appropriate starter cultures are used. For this purpose, LAB and yeasts with desirable characteristics should be isolated.
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42.
  •  
43.
  •  
44.
  • Olstorpe, Matilda, et al. (författare)
  • Microbial changes during storage of moist crimped cereal barley grain under Swedish farm conditions
  • 2010
  • Ingår i: Animal Feed Science and Technology. - Amsterdam, Netherlands : Elsevier. - 0377-8401 .- 1873-2216. ; 156:1-2, s. 37-46
  • Tidskriftsartikel (refereegranskat)abstract
    • This Study investigated feed hygiene during airtight storage of non-dried barley grain under farm conditions. Microorganisms on the grain were sampled and quantified in seven Swedish firms throughout the storage period using culture dependent methods. The dominant lactic acid bacteria (LAB) and yeasts were identified by rRNA gene sequencing and moulds by morphological characterisation. Moisture content (MC) and pH of the grain were also monitored. It was difficult to obtain the optimal MC(0.30-0.45 g/g) that is necessary to initiate fermentation in the grain. Feed hygiene was maintained during storage of cereals when MC below 0.17 g/g. Intermediate MC (0.17-0.23 g/g) of the grains was conducive to mould growth, including growth of potential producers of mycotoxins, which can diminish feed safety and nutritional value. Enterobacteriaceae were found in all barleys, even at low MC, but their numbers were substantially decreased when the number of LAB was high. True fermentation of moist crimped cereal grains was only obtained on one farm with all initial barley MC of 0.3 g/g. Here, LAB reached high numbers during storage, whereas numbers of spoilage microorganisms that may reduce feed hygiene decreased considerably. However, the pH of the barley did not differ among farms. Storage stability in airtight stored barley may thus be the result of low oxygen tension, viz. airtight storage, and competition for nutrients by the microorganisms, rather than formation of lactic acid. At harvest, Enterococcus caccae dominated the LAB Population in five barleys and Lactobacillus fermentum at the remaining two. The dominant yeast species were Aureobasidium pullulans, Cryptococcus wieringae, Kazachstania aerobia and Rhodotorula glutinis. After storage, L fermentum was dominant among the LAB. The yeast species composition was highly diverse and differed among barleys. Among others, C. wieringae, Debaryomyces hansenii, K. aerobia, R. glutinis and Sporobolomyces ruberrimus were detected. This Study shows that the microbial population in airtight stored moist barley is highly diverse and not predictable. Thus, it may be necessary to influence the microbial population in the storage system by adding a starter culture.
  •  
45.
  • Olstorpe, Matilda, et al. (författare)
  • Pichia anomala in grain biopreservation
  • 2011
  • Ingår i: Antonie van Leeuwenhoek. - : Springer Science and Business Media LLC. - 0003-6072 .- 1572-9699. ; 99, s. 57-62
  • Tidskriftsartikel (refereegranskat)abstract
    • Cereal grain is a major component of food and feed in large parts of the world. The microbial flora on cereal grains may interfere with hygiene and storage stability, palatability and bioavailability of minerals and proteins may depend on the composition of the microbial population. Therefore, it is of primary interest to control the microbial species present on cereal grain. Inoculation of the biocontrol yeast Pichia anomala to cereal feed grain improved feed hygiene by reduction of moulds and Enterobacteriaceae, and enhanced the nutritional value by increasing the protein content and reducing the concentration of the antinutritional compound phytate. P. anomala strains showed a high phytase activity, for some strains also considerable extracellular phytase activity was observed. A certain maximum in biomass concentration was never exceeded indicating cell density induced growth inhibition of P. anomala.
  •  
46.
  • Olstorpe, Matilda, et al. (författare)
  • Pichia anomala yeast improves feed hygiene during storage of moist crimped barley grain under Swedish farm conditions
  • 2010
  • Ingår i: Animal Feed Science and Technology. - Amsterdam, Netherlands : Elsevier BV. - 0377-8401 .- 1873-2216. ; 156, s. 47-56
  • Tidskriftsartikel (refereegranskat)abstract
    • Preservation of moist crimped cereal grain is made feasible through fermentation by lactic acid bacteria. Climatic variations make it difficult to harvest at moisture contents (0.30-0.45g/g) to support optimal fermentation under practical conditions. Therefore, the yeast, Pichia anomala J121, previously found to prevent mould spoilage and improve preservation of moist grain in malfunctioning airtight silos, was added to moist crimped cereal grain stored in large plastic tubes. Freshly harvested barley grain was crimped and inoculated with P. anomala (105 colony-forming units/g grain). Due to the local weather conditions, harvest was delayed and moisture content in the cereal grain had decreased to 0.16-0.18g/g. P. anomala was inoculated into three batches of barley, each comprising 16tonnes packed into large plastic tubes. Three additional sets of plastic tubes were packed with cereal grain without addition of P. anomala. The grain tubes were left closed for 5 months, after which feeding to cattle commenced. In both the P. anomala inoculated and the control barley, the population diversity of lactic acid bacteria (LAB) was very high over the duration of storage. However, the dominant LAB shifted over the course of storage to Pediococcus pentosaceus and Lactobacillus paracasei, in inoculated and control barley, respectively. The yeast population in the inoculated barley was totally dominated by P. anomala during the entire storage period. In the control grain, the yeast population was more diverse, displaying shifts in the dominant species during storage. Pichia burtonii was the dominant species at the last sampling occasion. In P. anomala inoculated barley, numbers of naturally occurring moulds were reduced by about two log units, and the number of Enterobacteriaceae was reduced to below detection.
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47.
  • Olstorpe, Matilda, et al. (författare)
  • Population diversity of Yeasts and lactic acid bacteria in pig feed fermented with whey, wet wheat distillers' grains, or water at different temperatures
  • 2008
  • Ingår i: Applied and Environmental Microbiology. - Washington, USA : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 74:6, s. 1696-1703
  • Tidskriftsartikel (refereegranskat)abstract
    • The diversity of populations of yeast and lactic acid bacteria (LAB) in pig feeds fermented at 10, 15, or 20 degrees C was characterized by rRNA gene sequencing of isolates. The feeds consisted of a cereal grain mix blended with wet wheat distillers' grains (WWDG feed), whey (W feed), or tap water (WAT feed). Fermentation proceeded for 5 days without disturbance, followed by 14 days of daily simulated feed outtakes, in which 80% of the contents were replaced with fresh feed mixtures. In WWDG feed, Pichia galeiformis became the dominant yeast species, independent of the fermentation temperature and feed change. The LAB population was dominated by Pediococcus pentosaceus at the start of the fermentation period. After 3 days, the Lactobacillus plantarum population started to increase in feeds at all temperatures. The diversity of LAB increased after the addition of fresh feed components. In W feed, Kluyveromyces marxianus dominated, but after the feed change, the population diversity increased. With increasing fermentation temperatures, there was a shift toward Pichia membranifaciens as the dominant species. L. plantarum was the most prevalent LAB in W feed. The WAT feed had a diverse microbial flora, and the yeast population changed throughout the whole fermentation period. Pichia anomala was the most prevalent yeast species, with increasing occurrence at higher fermentation temperatures. Pediococcus pentosaceus was the most prevalent LAB, but after the feed change, L. plantarum started to proliferate. The present study demonstrates that the species composition in fermented pig feed may vary considerably, even if viable cell counts indicate stable microbial populations.
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48.
  • Olstorpe, Matilda, et al. (författare)
  • Screening of yeast strains for phytase activity
  • 2009
  • Ingår i: FEMS yeast research (Print). - Oxford, United Kingdom : Oxford University Press. - 1567-1356 .- 1567-1364. ; 9:3, s. 478-488
  • Tidskriftsartikel (refereegranskat)abstract
    • A screening method was developed to elucidate the ability of different yeast strains to utilize phytic acid as sole phosphorus source. The growth test in liquid culture in a microtiter plate with phytic acid as sole phosphorus source was shown to be a reliable, fast and easy-to-use screening method. We tested 122 strains from 61 species with our method and observed growth differences among species and strains that were not detectable on solid medium. Specific phytase activities were measured for 10 yeasts strains, selected due to their strong growth in the liquid medium. Strains of Arxula adeninivorans and Pichia anomala reached the highest volumetric phytase activities. Arxula adeninivorans also displayed the highest intra- and extracellular specific activities. There were large differences in both extra- and intracellular phytase activities among species. Strain-specific extracellular phytase activities were detected in P. anomala. The presence of free phosphate in the media completely suppressed the extracellular phytase activity and also reduced intracellular phytase activity for all tested yeast strains.
  •  
49.
  • Olstorpe, Matilda, et al. (författare)
  • Strain-and temperature-dependent changes of fatty acid composition in Wickerhamomyces anomalus and Blastobotrys adeninivorans
  • 2014
  • Ingår i: Biotechnology and Applied Biochemistry. - : Wiley. - 0885-4513 .- 1470-8744. ; 61, s. 45-50
  • Tidskriftsartikel (refereegranskat)abstract
    • The fatty acid (FA) profiles of two strains of the yeasts Wickerhamomyces anomalus and Blastobotrys (Arxula) adeninivorans at cultivation temperatures from 15 to 30 degrees C were characterized. Besides the common even-numbered C16 and C18 FAs, substantial proportions of the uneven-numbered C17:1 were found in both species. C18:3(n-3) (alpha linolenic acid) made up to 3% of the total FAs in all strains. Considerable strain differences occurred, with regard to both the presence of single FAs and parameters like the double binding index (DBI) and C16:C18 ratio. W. anomalus J121 formed C18:1(n-5) (up to 10.9% of the total FAs) but no C18:1(n-7), whereas in W. anomalusVKM160, no C18:1(n-5) was found but up to 14.6% C18:1(n-7). Similarly, B. adeninivoransCBS 8244 formed exclusively C18:1(n-7) (maximum 9%) and CBS 7377 C18:1(n-5) (maximum 12.6%). W. anomalus J121 had the lowest DBI (0.72) at 15 degrees C and the highest (0.92) at 20 degrees C, at which point the values decreased with increasing temperatures. In W. anomalusVKM160 and both B. adeninivorans strains, DBI was highest at 15 degrees C and decreased with increasing temperature. In J121, the C16:C18 ratio was highest at 15 degrees C, decreasing at higher temperatures, whereas in the other strains, the opposite trend was observed.
  •  
50.
  • Passoth, Volkmar (författare)
  • A mutation in the COX5 gene of the yeast Scheffersomyces stipitis alters utilization of amino acids as carbon source, ethanol formation and activity of cyanide insensitive respiration
  • 2011
  • Ingår i: Yeast. - : Wiley. - 0749-503X .- 1097-0061. ; 28, s. 309-320
  • Tidskriftsartikel (refereegranskat)abstract
    • Scheffersomyces stipitis PJH was mutagenized by random integrative mutagenesis and the integrants were screened for lacking the ability to grow with glutamate as sole carbon source. One of the two isolated mutants was damaged in the COX5 gene, which encodes a subunit of the cytochrome c oxidase. BLAST searches in the genome of Sc. stipitis revealed that only one singular COX5 gene exists in Sc. stipitis, in contrast to Saccharomyces cerevisiae, where two homologous genes are present. Mutant cells had lost the ability to grow with the amino acids glutamate, proline or aspartate and other non-fermentable carbon sources, such as acetic acid and ethanol, as sole carbon sources. Biomass formation of the mutant cells in medium containing glucose or xylose as carbon source was lower compared with the wild-type cells. However, yields and specific ethanol formation of the mutant were much higher, especially under conditions of higher aeration. The mutant cells lacked both cytochrome c oxidase activity and cyanide-sensitive respiration, whereas ADH and PDC activities were distinctly enhanced. SHAM-sensitive respiration was obviously essential for the fermentative metabolism, because SHAM completely abolished growth of the mutant cells with both glucose or xylose as carbon source. Copyright. (C) 2011 John Wiley & Sons, Ltd.
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