| 1. |
- Bakeeva, Albina, et al.
(författare)
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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
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Ingår i: Livestock Science. - : Elsevier BV. - 1871-1413 .- 1878-0490. ; 199, s. 14-21
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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)
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The Potential of Kluyveromyces marxianus to Produce Low-FODMAP Straight-Dough and Sourdough Bread: a Pilot-Scale Study
- 2021
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Ingår i: Food and Bioprocess Technology. - : Springer Science and Business Media LLC. - 1935-5130 .- 1935-5149. ; 14, s. 1920-1935
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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)
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Yeasts and bacteria associated with kocho, an Ethiopian fermented food produced from enset (Ensete ventricosum)
- 2019
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Ingår i: Antonie van Leeuwenhoek. - : Springer Science and Business Media LLC. - 0003-6072 .- 1572-9699. ; 112, s. 651-659
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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)
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Dekkera bruxellensis-spoilage yeast with biotechnological potential, and a model for yeast evolution, physiology and competitiveness
- 2015
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Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1356 .- 1567-1364. ; 15, s. 9-
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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)
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Fermentation characteristics of Dekkera bruxellensis strains
- 2010
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Ingår i: Applied Microbiology and Biotechnology. - New York, USA : Springer. - 0175-7598 .- 1432-0614. ; 87:4, s. 1487-1497
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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)
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Fermentation of lignocellulosic hydrolysate by the alternative industrial ethanol yeast Dekkera bruxellensis
- 2011
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Ingår i: Letters in Applied Microbiology. - Malden, USA : Wiley-Blackwell. - 0266-8254 .- 1472-765X. ; 53:1, s. 73-78
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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)
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Oleaginous yeast as a component in fish feed
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
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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)
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Physiological requirements for growth and competitiveness of Dekkera bruxellensis under oxygen-limited or anaerobic conditions
- 2012
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Ingår i: Yeast. - : Wiley. - 1097-0061 .- 0749-503X. ; 29:7, s. 265-274
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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)
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Temperature-dependent changes in the microbial storage flora of birch and spruce sawdust
- 2014
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Ingår i: Biotechnology and Applied Biochemistry. - : Wiley. - 0885-4513 .- 1470-8744. ; 61, s. 58-64
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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)
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The effect of a combined biological and thermo-mechanical pretreatment of wheat straw on energy yields in coupled ethanol and methane generation
- 2015
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 194, s. 7-13
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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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