| 1. |
- Båth, Klara, et al.
(författare)
-
Microbiota of an unpasteurised cellar-stored goat cheese from northern Sweden
- 2012
-
Ingår i: Agricultural and Food Science. - Helsinki, Finland : M T T / Agrifood Research Finland. - 1459-6067 .- 1795-1895. ; 21:2, s. 197-203
-
Tidskriftsartikel (refereegranskat)abstract
- This qualitative study reports on lactic acid bacteria (LAB), yeasts and moulds isolated from three artisanal Swedish cellar-stored goat cheeses aged for 1, 3 and 5 months. Starter culture LAB dominated in the younger cheeses, and Leuconostoc pseudomesenteroides, common in raw goats' milk, had persisted from the unpasteurised milk into all the cheeses. Non-starter LAB dominated in the 5 month cheese, in particular, Lactobacillus sakei, a meat-associated LAB not previously isolated from cheese. Debaryomyces hansenii, and Penicillium and Mucor species were dominant among the yeasts and moulds, respectively. The cheese rind was not formed primarily from Penicillium species as in traditional cheeses such as Camembert - rather, mycelium from Mucor mucedo contributed to rind formation. Mould species known to produce sterigmatocystin, aflatoxins or ochratoxin A in cheese were not isolated in this study; growth of mycotoxigenic Aspergilli may have been inhibited by the cool conditions in the earth-cellar (4-6 degrees C).
|
|
| 2. |
- Leong, Su-lin L., et al.
(författare)
-
Genome and physiology of the ascomycete filamentous fungus Xeromyces bisporus, the most xerophilic organism isolated to date
- 2015
-
Ingår i: Environmental Microbiology. - Hoboken, USA : Wiley-Blackwell. - 1462-2912 .- 1462-2920. ; 17:2, s. 496-513
-
Tidskriftsartikel (refereegranskat)abstract
- Xeromyces bisporus can grow on sugary substrates down to 0.61, an extremely low water activity. Its genome size is approximately 22Mb. Gene clusters encoding for secondary metabolites were conspicuously absent; secondary metabolites were not detected experimentally. Thus, in its dry' but nutrient-rich environment, X.bisporus appears to have relinquished abilities for combative interactions. Elements to sense/signal osmotic stress, e.g. HogA pathway, were present in X.bisporus. However, transcriptomes at optimal (approximate to 0.89) versus low a(w) (0.68) revealed differential expression of only a few stress-related genes; among these, certain (not all) steps for glycerol synthesis were upregulated. Xeromyces bisporus increased glycerol production during hypo- and hyper-osmotic stress, and much of its wet weight comprised water and rinsable solutes; leaked solutes may form a protective slime. Xeromyces bisporus and other food-borne moulds increased membrane fatty acid saturation as water activity decreased. Such modifications did not appear to be transcriptionally regulated in X.bisporus; however, genes modulating sterols, phospholipids and the cell wall were differentially expressed. Xeromyces bisporus was previously proposed to be a chaophile', preferring solutes that disorder biomolecular structures. Both X.bisporus and the closely related xerophile, Xerochrysium xerophilum, with low membrane unsaturation indices, could represent a phylogenetic cluster of chaophiles'.
|
|
| 3. |
- Leong, Su-lin L., et al.
(författare)
-
The extreme xerophilic mould Xeromyces bisporus : Growth and competition at various water activities
- 2011
-
Ingår i: International Journal of Food Microbiology. - Amsterdam, Netherlands : Elsevier. - 0168-1605 .- 1879-3460. ; 145:1, s. 57-63
-
Tidskriftsartikel (refereegranskat)abstract
- Little is known about the mould, Xeromyces bisporus, unique in its strong xerophilicity and ability to grow at water activity (a(w)) 0.62, lower than for any other known organism. The linear growth rates of one fast and one slow-growing strain of X. bisporus were assessed at 20, 25, 30 and 37 degrees C on solid agar media containing a mixture of glucose and fructose to reduce a(w) to 0.94, 0.88, 0.84, 0.80, 0.76 and 0.66. Growth rates of xerophilic species closely related to X. bisporus, viz. Chrysosporium Mops, C. xerophilum and Monascus eremophilus, were also assessed. Optimal conditions for growth of both X. bisporus strains were approx. 0.84 a(w) and 30 degrees C, despite FRR 2347 growing two- to five-fold faster than CBS 185.75. X. bisporus FRR 2347 even grew well at 0.66 a(w) (0.48 mm/day). C. Mops and C xerophilurn were more tolerant of high a(w) than X. bisporus. and could be differentiated from each other based on: the faster growth of C. xerophilum; its preference for temperatures >= 30 degrees C and a(w) >= 0.94 (c.f. <= 25 degrees C and similar to 0.88 a(w) for C Mops); and its ability to grow at 0.66 a(w), which is the lowest a(w) reported to date for this species. M. eremophilus grew slowly (max. 0.4 mm/day) even in its optimal conditions of similar to 0.88 a(w) and 25 degrees C. To investigate the competitive characteristics of X. bisporus at low a(w), both X. bisporus strains were grown in dual-culture with xerotolerant species Aspergillus flavus and Penicillium roqueforti, and xerophilic species A. penicillioides, C. Mops, C. xerophilum and Eurotium chevalieri, on glucose-fructose agar plates at 0.94, 0.84, 0.80 and 0.76 a(w) and at 25 degrees C. Growth rates and types of interactions were assessed. Excretion of inhibitory substances acting over a long-range was not observed by any species; inhibitors acting over a short-range that temporarily slowed competitors' growth or produced a protective zone around the colony were occasionally observed for A. penicillioides, C. Mops and C. xerophilum. Instead, rapid growth relative to the competitor was the most common means of dominance. The xerotolerant species. A. flavus and P. roqueforti were dominant over X. bisporus at 0.94 a(w). E. chevalieri was often dominant due to its rapid growth over the entire a(w) range. At a(w) < 0.80, X. bisporus was competitive because it grew faster than the other species examined. This supports the concept that its ideal environmental niche is sugary foods with low a(w).
|
|
| 4. |
- Vinnere Pettersson, Olga, et al.
(författare)
-
Phylogeny and intraspecific variation of the extreme xerophile, Xeromyces bisporus
- 2011
-
Ingår i: Fungal Biology. - Oxon, United Kingdom : Elsevier. - 1878-6146 .- 1878-6162. ; 115:11, s. 1100-1111
-
Tidskriftsartikel (refereegranskat)abstract
- The filamentous ascomycete Xeromyces bisporus is an extreme xerophile able to grow down to a water activity of 0.62. We have inferred the phylogenetic position of Xeromyces in relation to other xerophilic and xerotolerant fungi in the order Eurotiales. Using nrDNA and betatubulin sequences, we show that it is more closely related to the xerophilic food-borne species of the genus Chrysosporium, than to the genus Monascus. The taxonomy of X. bisporus and Monascus is discussed. Based on physiological, morphological, and phylogenetic distinctiveness, we suggest that Xeromyces should be retained as a separate genus.
|
|
| 5. |
- Bakeeva, Albina, et al.
(författare)
-
Distribution of mycotoxins produced by Penicillium spp. inoculated in apple jam and creme fraiche during chilled storage
- 2019
-
Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 292, s. 13-20
-
Tidskriftsartikel (refereegranskat)abstract
- Estimations of consumer exposure to mycotoxins through surveillance of mycotoxins in the food trade are well described, but the exposure due to mouldy food in private homes is not known, and may result from removing visible mould on food and eating the rest. In this study, we followed the growth of Penicillium expansum on the surface of apple jam and Penicillium verrucosum on creme fraiche, as well as production and distribution of fungal metabolites throughout the sample (approx. 6 cm high divided into three equal layers), using a multianalyte method, over time (up to 28 days) and at 4, 8 and 15 degrees C.Growth rates and apparent lag times for P. expansum in apple jam at different temperatures were estimated by fitting to the Baranyi model. The growth rates were 1.7, 2.7 and 4.3 mm day(-1) for storage at 4, 8 and 15 degrees C, respectively; apparent lag times decreased with increasing storage temperature and were 10.6, 7.9 and 2.6 days at corresponding temperatures. Patulin and roquefortine C were identified and quantified, among other fungal metabolites. Patulin was detected in all 2-cm layers of the apple jam at 15 degrees C. Concentrations in the upper two layers of the jar corresponded to exposures exceeding the health based guidance value (HBGV) for a normal serving size. Consequently, removal of the mouldy part is insufficient to avoid unhealthy exposure. In contrast to patulin, roquefortine C was also produced at 4 degrees C.The growth of P. verrucosum on creme fraiche was very restricted and could not be modelled. Despite the small colony (8 +/- 0.5 mm in diameter), ochratoxin A and citrinin were detected after 21 days at 15 degrees C in the top 2 cm layer (including the fungal colony), and at concentrations in a normal serving corresponding to an exposure above the HBGV established by EFSA for both mycotoxins. Questiomycin A, an antibiotic, was also produced in creme fraiche but in contrast to the two mycotoxins, was detected throughout all layers of the creme fraiche and was produced also at 4 and 8 degrees C.As a complement to a previous study, we also present production and the distribution of major fungal metabolites in apple jam and creme fraiche for some additional fungal strains (P. crustosum, P. roqueforti and P. verrucosum on apple jam and P. expansum on creme fraiche). A pilot study investigating the effect of inoculation size on toxin production may have implications for the best inoculum to use in experimental studies.
|
|
| 6. |
- Barbosa, R. N., et al.
(författare)
-
Phylogenetic analysis of Monascus and new species from honey, pollen and nests of stingless bees
- 2017
-
Ingår i: Studies in mycology. - : Westerdijk Fungal Biodiversity Institute. - 0166-0616 .- 1872-9797. ; :86, s. 29-51
-
Tidskriftsartikel (refereegranskat)abstract
- The genus Monascus was described by van Tieghem (1884) to accommodate M. ruber and M. mucoroides, two species with non-ostiolate ascomata. Species delimitation in the genus is still mainly based on phenotypic characters, and taxonomic studies that include sequence data are limited. The genus is of economic importance. Species are used in fermented Asian foods as food colourants (e.g. 'red rice' (ang-kak, angka)) and found as spoilage organisms, and recently Monascus was found to be essential in the lifecycle of stingless bees. In this study, a polyphasic approach was applied combining morphological characters, ITS, LSU, beta-tubulin, calmodulin and RNA polymerase II second largest subunit sequences and extrolite data, to delimit species and to study phylogenetic relationships in Monascus. Furthermore, 30 Monascus isolates from honey, pollen and nests of stingless bees in Brazil were included. Based on this polyphasic approach, the genus Monascus is resolved in nine species, including three new species associated with stingless bees (M. flavipigmentosus sp. nov., M. mellicola sp. nov., M. recifensis sp. nov., M. argentinensis, M. floridanus, M. lunisporas, M. pallens, M. purpureus, M. ruber), and split in two new sections (section Floridani sect. nov., section Rubri sect. nov.). Phylogenetic analysis showed that the xerophile Monascus eremophilus does not belong in Monascus and monophyly in Monascus is restored with the transfer of M. eremophilus to Penicillium (P. eremophilum comb. nov.). A list of accepted and excluded Monascus and Basipetospora species is given, together with information on (ex-)types cultures and barcode sequence data.
|
|
| 7. |
- 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.
|
|
| 8. |
- Hedén, Su-Lin, et al.
(författare)
-
Biocontrol efficacy of Wickerhamomyces anomalus in moist maize storage
- 2014
-
Ingår i: African journal of biotechnology. - 1684-5315. ; 13, s. 4208-4214
-
Tidskriftsartikel (refereegranskat)abstract
- White maize cultivar ‘Kasai’ was harvested and stored moist, sealed in airtight plastic barrels, with and without inoculation of the biocontrol yeast, Wickerhamomyces anomalus. Microbes were enumerated at harvest and after 2, 5 and 8 months of storage. Moist storage of maize yielded a type of fermentation, in which high levels of lactic acid bacteria (LAB) naturally present on maize (108 cfu/g), were maintained throughout storage. Activity of LAB in both control and inoculated maize likely contributed to the decline in Enterobacteriaceae to < 10 cfu/g after 2 months storage, a good outcome for food and feed hygiene. The biocontrol yeast, W. anomalus, appeared to have died out in the inoculated treatment after 2 months; nevertheless, a positive effect was seen in significantly reduced mould counts to < 100 cfu/g compared with the uninoculated maize. Reducing moulds during storage minimises the risk for mycotoxin production. Storage for 8 months with the biocontrol yeast did not appear to affect nutritional parameters of the maize, such as dry matter, crude protein and total amino acids. Compared with the uninoculated control, inoculated maize had significantly better contents of three amino acids (alanine, aspartic acid and glycine), but poorer contents of six amino acids (arginine, lysine, ornithine, proline, serine and tyrosine). The absence of nutritional improvement in inoculated maize could be due to the poor survival of the biocontrol yeast, and altered formulation practices may address this.
|
|
| 9. |
- Hedén, Su-Lin
(författare)
-
Glycerol enhances fungal germination at the water-activity limit for life
- 2017
-
Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 19, s. 947-967
-
Tidskriftsartikel (refereegranskat)abstract
- For the most-extreme fungal xerophiles, metabolic activity and cell division typically halts between 0.700 and 0.640 water activity (approximately 70.0-64.0% relative humidity). Here, we investigate whether glycerol can enhance xerophile germination under acute water-activity regimes, using an experimental system which represents the biophysical limit of Earth's biosphere. Spores from a variety of species, including Aspergillus penicillioides, Eurotium halophilicum, Xerochrysium xerophilum (formerly Chrysosporium xerophilum) and Xeromyces bisporus, were produced by cultures growing on media supplemented with glycerol (and contained up to 189 mg glycerol g dry spores(-1)). The ability of these spores to germinate, and the kinetics of germination, were then determined on a range of media designed to recreate stresses experienced in microbial habitats or anthropogenic systems (with water-activities from 0.765 to 0.575). For A. penicillioides, Eurotium amstelodami, E. halophilicum, X. xerophilum and X. bisporus, germination occurred at lower water-activities than previously recorded (0.640, 0.685, 0.651, 0.664 and 0.637 respectively). In addition, the kinetics of germination at low water-activities were substantially faster than those reported previously. Extrapolations indicated theoretical water-activity minima below these values; as low as 0.570 for A. penicillioides and X. bisporus. Glycerol is present at high concentrations (up to molar levels) in many types of microbial habitat. We discuss the likely role of glycerol in expanding the water-activity limit for microbial cell function in relation to temporal constraints and location of the microbial cell or habitat. The findings reported here have also critical implications for understanding the extremes of Earth's biosphere; for understanding the potency of disease-causing microorganisms; and in biotechnologies that operate at the limits of microbial function.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Lantz, Henrik, et al.
(författare)
-
Xerochrysium gen. nov. and Bettsia, genera encompassing xerophilic species of Chrysosporium
- 2013
-
Ingår i: IMA fungus. - : Springer Science and Business Media LLC. - 2210-6340 .- 2210-6359. ; 4, s. 229-241
-
Tidskriftsartikel (refereegranskat)abstract
- On the basis of a study of ITS sequences, Vidal et al. (Rev. Iber. Micol. 17: 22, 2000) recommended that the genus Chrysosporium be restricted to species belonging to Onygenales. Using nrLSU genes, we studied the majority of clades examined by Vidal et al. and showed that currently accepted species in Chrysosporium phylogenetically belong in six clades in three orders. Surprisingly, the xerophilic species of Chrysosporium, long thought to be a single grouping away from the majority of Chrysosporium species, occupy two clades, one in Leotiales, the other in Eurotiales. Species accepted in Leotiales are related to the sexual genus Bettsia. One is the type species B. alvei, and related asexual strains classified as C. farinicola, the second is C. fastidium transferred to Bettsia as B. fastidia. Species in the Eurotiales are transferred to Xerochrysium gen. nov., where the accepted species are X. xerophilum and X. dermatitidis, the correct name for C. inops on transfer to Xerochrysium. All accepted species are extreme xerophiles, found in dried and concentrated foods.
|
|
| 13. |
- Vinnere Pettersson, Olga, et al.
(författare)
-
Fungal Xerophiles (Osmophiles)
- 2011
-
Ingår i: Encyclopedia of Life Sciences. - : Wiley.
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
