Thermoresistance in black yeasts is associated with halosensitivity and HPP tolerance, but not with UV tolerance or sanitizer tolerance

Journal of Food Protection ◽

10.4315/jfp-21-314 ◽

2021 ◽

Author(s):

Shiyu Cai ◽

Abigail Snyder

Keyword(s):

Food Production ◽

Uv Light ◽

High Pressure Processing ◽

Black Yeast ◽

Black Yeasts ◽

Strain Variation ◽

Yeast Strains ◽

Uv Tolerance ◽

Relative Stress ◽

Different Strains

Black yeasts can survive extreme conditions in food production owing to their polyextremotolerant character. However, significant strain-to-strain variation in black yeast thermoresistance has been observed. In this study, we assessed the variability in tolerance to nonthermal interventions among a collection of food-related black yeast strains. Variation in tolerance to UV light treatment, high pressure processing, sanitizers, and osmotic pressure was observed within each species. The two strains previously shown to possess high thermotolerance, Exophiala phaeomuriformis FSL-E2-0572 and Exophiala dermatitidis YB-734, were also the most HPP tolerant, but were the least halotolerant. Meanwhile, Aureobasidium pullulans FSL-E2-0290 was the most UV and sanitizer tolerant, but had been shown to have relatively low thermoresistance. Fisher’s exact tests showed that thermoresistance in black yeasts was associated with HPP tolerance and inversely with halotolerance, but no association was found with UV tolerance or sanitizer tolerance. Collectively, the relative stress tolerance among strains varied across interventions. Given this variation, a broad range of different food products are susceptible to black yeast spoilage. Additionally, different strains should be selected in challenge studies specific to the intervention. (1312/2000 characters)

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Impact of black yeasts on the durability of polyurethane foam in tropical conditions in Vietnam

E3S Web of Conferences ◽

10.1051/e3sconf/202016902007 ◽

2020 ◽

Vol 169 ◽

pp. 02007

Author(s):

Hoai Nguyen Thu ◽

Hong Do Thi Thu ◽

Cuong Ngo Cao ◽

Thinh Do Tat ◽

V.N. Sereda

Keyword(s):

Tensile Strength ◽

Urease Activity ◽

Climatic Conditions ◽

Black Yeast ◽

Black Yeasts ◽

Its2 Region ◽

Pu Foam ◽

Yeast Strains ◽

Tropical Conditions ◽

The Impact

Polyurethane (PU) is a material that is widely used in industries. However, tropical climatic conditions in Vietnam often make the durability of PU lower than temperate climatic conditions. One of the causes of this problem is the biodegradation of microorganisms. In this study, biological characteristics of black yeast on PU is evaluated, thereby, initially assessing the impact of black yeast on the durability of PU in tropical conditions. Ten strains of black yeast were isolated from used PU foam samples in Vietnam. These black yeast strains were tested for enzyme activity including: urease activity, protease activity, polyurethanase activity. There were two strains selected to identify based on sequence analysis of the ITS1/ITS2 region, they belong to genus Aureobasidium. VN1Y3 was strain selected for biodegradability testing of PU foam samples. After 28 days of testing, the PU foam samples that have been infected with black yeasts have a change compared to the control in terms of color, surface, tensile strength, elongation. Research results have showed the impact of black yeast on the durability of PU.

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Intermediate thermoresistance in black yeast asexual cells variably increases with culture age, promoting survival and spoilage in thermally processed shelf-stable foods

Journal of Food Protection ◽

10.4315/jfp-21-103 ◽

2021 ◽

Author(s):

Shiyu Cai ◽

Emilia Rico-Munoz ◽

Abigail Snyder

Keyword(s):

Black Yeast ◽

Black Yeasts ◽

Maple Syrup ◽

Apple Cider ◽

Culture Age ◽

Heat Resistant ◽

Challenge Study ◽

Food Spoilage Fungi ◽

Intermediate Degree ◽

Spoilage Fungi

Black yeasts are a functional group that has caused spoilage in cold-filled and hot-filled beverages as well as other water activity (a w )-controlled food products. We established quantitative thermoresistance parameters for the inactivation of 12 Aureobasidium and Exophiala isolates through isothermal experiments and a challenge study. Culture age (2-day vs. 28-day) variably affected the thermoresisitance among the black yeast strains. Variation in thermoresistance exists within each genus, but the two most resistant strains were the Exophiala isolates. The two most heat resistant isolates were E. phaeomuriformis FSL-E2-0572 with a D 60 -value of 7.69±0.63 min in 28-day culture and E. dermatitidis YB-734 with a D 60 -value of 16.32±2.13 min in 28-day culture. While these thermoresistance levels were, in some cases, greater than those for conidia and vegetative cells from other common food spoilage fungi, they were much more sensitive than the ascospores of heat resistant molds most associated with spoilage of hot-filled products. However, given that black yeasts have caused spoilage in hot-filled products, we hypothesized that this intermediate degree of thermoresistance may support survival following introduction during active cooling before package seals have formed. A challenge study was performed in an acidic (apple cider) and a w -controlled (maple syrup) product to evaluate survival. When apple cider was hot-filled at 82C, black yeast counts were reduced by 4.1-log CFU/ml 24 h after the heat treatment, but the survivors increased up to 6.7-log CFU/ml after two weeks. In comparison, the counts were below the detection limit after both 24 h and 14 days of shelf-life in both products when filled at their boiling points. This suggests that ensuring water microbial quality in cooling tunnels and nozzle sanitation may be essential in mitigating the introduction of these fungi.

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Development of an Improved Carotenoid Extraction Method to Characterize the Carotenoid Composition under Oxidative Stress and Cold Temperature in the Rock Inhabiting Fungus Knufia petricola A95

Journal of Fungi ◽

10.3390/jof4040124 ◽

2018 ◽

Vol 4 (4) ◽

pp. 124 ◽

Cited By ~ 6

Author(s):

Kerstin Flieger ◽

Nicole Knabe ◽

Jörg Toepel

Keyword(s):

Oxidative Stress ◽

Stress Responses ◽

Stress Factors ◽

Black Yeast ◽

Black Yeasts ◽

Protective Agent ◽

Extraction And Separation ◽

Carotenoid Composition ◽

Other Substances ◽

Promising Source

Black yeasts are a highly specified group of fungi, which are characterized by a high resistance against stress factors. There are several factors enabling the cells to survive harsh environmental conditions. One aspect is the pigmentation, the melanin black yeasts often display a highly diverse carotenoid spectrum. Determination and characterization of carotenoids depend on an efficient extraction and separation, especially for black yeast, which is characterized by thick cell walls. Therefore, specific protocols are needed to ensure reliable analyses regarding stress responses in these fungi. Here we present both. First, we present a method to extract and analyze carotenoids and secondly we present the unusual carotenoid composition of the black yeast Knufia petricola A95. Mechanical treatment combined with an acetonitrile extraction gave us very good extraction rates with a high reproducibility. The presented extraction and elution protocol separates the main carotenoids (7) in K. petricola A95 and can be extended for the detection of additional carotenoids in other species. K. petricola A95 displays an unusual carotenoid composition, with mainly didehydrolycopene, torulene, and lycopene. The pigment composition varied in dependency to oxidative stress but remained relatively constant if the cells were cultivated under low temperature. Future experiments have to be carried out to determine if didehydrolycopene functions as a protective agent itself or if it serves as a precursor for antioxidative pigments like torulene and torularhodin, which could be produced after induction under stress conditions. Black yeasts are a promising source for carotenoid production and other substances. To unravel the potential of these fungi, new methods and studies are needed. The established protocol allows the determination of carotenoid composition in black yeasts.

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Differentiation of Yeast Cultures in Ruminant Feedingstuffs Using a Rapid DNA Fingerprinting Technique

Proceedings of the British Society of Animal Production (1972) ◽

10.1017/s0308229600026489 ◽

1994 ◽

Vol 1994 ◽

pp. 101-101

Author(s):

Elizabeth Moore ◽

Denis R. Headon

Keyword(s):

Sodium Dodecyl ◽

Yeast Cells ◽

Microbial Populations ◽

Yeast Culture ◽

Yeast Cultures ◽

Yeast Strains ◽

Genetic Sequences ◽

Polymerase Chain ◽

Different Strains ◽

Triton X

Research indicates that certain yeast strains are beneficial in their capacity to stimulate key microbial populations. This stimulation is strain specific with similar yeast strains exerting their effect on totally different microbial populations. Future yeast culture supplements may contain mixtures of different strains designed to suit specific diets. This, therefore, requires the development of a rapid sensitive technique to differentiate among taxonomically similar yeast strains in animal diets. This technique, termed the Randomly Amplified Polymorphic DNA (RAPD) assay, is based upon the use of randomly designed short polynucleotide primers to amplify genetic sequences from the DNA of the desired yeast strain. Our objective involves the development of this technique to distinguish between closely related yeast strains present in feed. The feed sample investigated was a standard cattle ration containing three strains of Saccharomyces cerevisiae (1026, 2045 and 2020) and Candida utilis 3001 at a concentration of 106 CFU/g respectively. Isolation of single colonies of yeast strains present was achieved by feed extraction in dilution buffer followed by plating a series of dilutions on rose-bengal agar. Thirty randomly selected colonies were cultured in YPD (1% yeast extract, 2% peptone, 2% glucose) broth for 24 - 30 hours at 30°C. Genomic DNA was isolated from yeast cells by standard methods based on subjection of the cells to vortex mixing in the presence of glass beads, triton X-100, sodium dodecyl sulphate, phenol and chloroform. Isolated DNA from randomly selected colonies was amplified by Polymerase Chain Reaction (PCR) for 45 cycles of 1 min at 94°C, 1 min at 36°C and 1 min at 72°C using randomly designed 10 bp primers.

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Innovative Technologies in Sustainable Food Production: High Pressure Processing

10.1016/b978-0-12-821233-2.00011-3 ◽

2021 ◽

pp. 145-153

Author(s):

Sven Karlović ◽

Tomislav Bosiljkov ◽

Damir Ježek ◽

Marinela Nutrizio ◽

Anet Režek Jambrak

Keyword(s):

High Pressure ◽

Food Production ◽

High Pressure Processing ◽

Sustainable Food ◽

Innovative Technologies ◽

Sustainable Food Production

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Comparative Transcriptomic Approach To Investigate Differences in Wine Yeast Physiology and Metabolism during Fermentation

Applied and Environmental Microbiology ◽

10.1128/aem.01251-09 ◽

2009 ◽

Vol 75 (20) ◽

pp. 6600-6612 ◽

Cited By ~ 29

Author(s):

Debra Rossouw ◽

Roberto Olivares-Hernandes ◽

Jens Nielsen ◽

Florian F. Bauer

Keyword(s):

Stress Responses ◽

Metabolic Regulation ◽

Wine Yeast ◽

Molecular Networks ◽

Comparative Approach ◽

Phenotypic Traits ◽

Phenotypic Differences ◽

Yeast Strains ◽

Industrial Strains ◽

Different Strains

ABSTRACT Commercial wine yeast strains of the species Saccharomyces cerevisiae have been selected to satisfy many different, and sometimes highly specific, oenological requirements. As a consequence, more than 200 different strains with significantly diverging phenotypic traits are produced globally. This genetic resource has been rather neglected by the scientific community because industrial strains are less easily manipulated than the limited number of laboratory strains that have been successfully employed to investigate fundamental aspects of cellular biology. However, laboratory strains are unsuitable for the study of many phenotypes that are of significant scientific and industrial interest. Here, we investigate whether a comparative transcriptomics and phenomics approach, based on the analysis of five phenotypically diverging industrial wine yeast strains, can provide insights into the molecular networks that are responsible for the expression of such phenotypes. For this purpose, some oenologically relevant phenotypes, including resistance to various stresses, cell wall properties, and metabolite production of these strains were evaluated and aligned with transcriptomic data collected during alcoholic fermentation. The data reveal significant differences in gene regulation between the five strains. While the genetic complexity underlying the various successive stress responses in a dynamic system such as wine fermentation reveals the limits of the approach, many of the relevant differences in gene expression can be linked to specific phenotypic differences between the strains. This is, in particular, the case for many aspects of metabolic regulation. The comparative approach therefore opens new possibilities to investigate complex phenotypic traits on a molecular level.

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Redox Interactions between Saccharomyces cerevisiae and Saccharomyces uvarum in Mixed Culture under Enological Conditions

Applied and Environmental Microbiology ◽

10.1128/aem.71.1.255-260.2005 ◽

2005 ◽

Vol 71 (1) ◽

pp. 255-260 ◽

Cited By ~ 48

Author(s):

Naoufel Cheraiti ◽

StÃ¯Â¿Â½phane Guezenec ◽

Jean-Michel Salmon

Keyword(s):

Saccharomyces Cerevisiae ◽

Mixed Culture ◽

Wine Yeast ◽

Redox Status ◽

Product Formation ◽

Hybrid Strain ◽

Saccharomyces Uvarum ◽

Yeast Strains ◽

Different Strains ◽

Different Cultures

ABSTRACT Wine yeast starters that contain a mixture of different industrial yeasts with various properties may soon be introduced to the market. The mechanisms underlying the interactions between the different strains in the starter during alcoholic fermentation have never been investigated. We identified and investigated some of these interactions in a mixed culture containing two yeast strains grown under enological conditions. The inoculum contained the same amount (each) of a strain of Saccharomyces cerevisiae and a natural hybrid strain of S. cerevisiae and Saccharomyces uvarum. We identified interactions that affected biomass, by-product formation, and fermentation kinetics, and compared the redox ratios of monocultures of each strain with that of the mixed culture. The redox status of the mixed culture differed from that of the two monocultures, showing that the interactions between the yeast strains involved the diffusion of metabolite(s) within the mixed culture. Since acetaldehyde is a potential effector of fermentation, we investigated the kinetics of acetaldehyde production by the different cultures. The S. cerevisiae-S. uvarum hybrid strain produced large amounts of acetaldehyde for which the S. cerevisiae strain acted as a receiving strain in the mixed culture. Since yeast response to acetaldehyde involves the same mechanisms that participate in the response to other forms of stress, the acetaldehyde exchange between the two strains could play an important role in inhibiting some yeast strains and allowing the growth of others. Such interactions could be of particular importance in understanding the ecology of the colonization of complex fermentation media by S. cerevisiae.

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Development of an Improved Carotenoid Extraction Method and Characterisation of the Carotenoid Composition under Oxidative and Cold Stress in the Rock Inhabiting Fungus Knufia Petricola A95

10.20944/preprints201810.0037.v1 ◽

2018 ◽

Author(s):

Kerstin Flieger ◽

Nicole Knabe ◽

Jörg Toepel

Keyword(s):

Oxidative Stress ◽

Stress Responses ◽

Stress Factors ◽

Black Yeast ◽

Black Yeasts ◽

Protective Agent ◽

Pigment Composition ◽

Carotenoid Composition ◽

Other Substances ◽

Promising Source

Black yeasts are a highly specified group of fungi, which are characterized by a high resistance against stress factors. There are several factors enabling the cells to survive harsh environmental conditions. One aspect is the pigmentation, besides the melanin black yeasts often display a highly diverse carotenoid spectrum. Determination and characterization of carotenoids depend on an efficient extraction and separation, therefore especially for black yeast, characterized by thick cell walls specific protocols are needed to ensure analyses regarding stress responses in these fungi. Here we present both, a method to extract and analyze carotenoids and the unusual carotenoid composition of the black yeast Knufia petriola A95. Mechanical treatment combined with an acetonitrile extraction gave us very good extraction rates with a high reproducibility. The presented extraction and elution protocol allows the separation of the main carotenoids (7) in K. petricola A95 and should be suitable for the detection of additional carotenoids in other species. K. petricola A95 displays an unusual carotenoid composition, with mainly didehydrolycopene, torulene and lycopene. The pigment composition varied in dependency to oxidative stress but remained relatively constant if the cells were cultivated under low temperature. Black yeasts are a promising source for carotenoid production and other substances. To unravel the potential of these fungi new methods and studies are needed. The established protocol allows the determination carotenoid composition in black yeasts. Oxidative stress results in an adaptation in pigment composition in K. petricola A95. Future experiments have to be carried out to determine if didehydrolycopene functions as a protective agent itself or if it serves as a precursor for antioxidative pigments like torulene and torularhodin, which could be produced after induction under stress conditions.

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Evaluation of Saccharomyces pastorianus impact to Sauvignon blanc chemical & sensory profile compared to different strains of S. cerevisiae/bayanus

BIO Web of Conferences ◽

10.1051/bioconf/20191202025 ◽

2019 ◽

Vol 12 ◽

pp. 02025

Author(s):

V. Troianou ◽

C. Toumpeki ◽

E. Dorignac ◽

C. Kogkou ◽

S. Kallithraka ◽

...

Keyword(s):

Sensory Profile ◽

Higher Alcohols ◽

Sauvignon Blanc ◽

Wine Analysis ◽

Yeast Strains ◽

Saccharomyces Pastorianus ◽

Cold Condition ◽

Fermentation Parameters ◽

Different Strains ◽

The Impact

Enhancing flavors and/or improving fermentation parameters through the use of different species of yeast strains is nowadays a frequent challenge in winemaking research, especially for aromatic varieties such as Sauvignon Blanc. In this work, the aim was to focus on the impact of a species not already studied in wine: Saccharomyces pastorianus. Twenty-two fermentations were conducted on a Sauvignon Blanc must by addition of different strains and mixtures of them by using two different inoculation temperatures. The must was inoculated in cold condition with two similar mixtures of S. pastorianus 1 or 2 (70%) and S. bayanus(30%), with S. pastorianus 1 or 2 alone, with the correspondent S. bayanusalone and with two other S. cerevisiae1 and 2 alone as well. For classic condition, the must was inoculated with only one mixture S. pastorianus1 (70%) / S. bayanus(30%), and respectively with S. pastorianus1, S. bayanus and S. cerevisiae 2 alone. Samples were taken all along the fermentations for both conditions in order to check chemical and microbial analyses as well as yeast implantations. The final wines were analysed for alcohol, glucose, fructose, all other classical wine analysis as well as for acetate esters, and higher alcohols. The results underlined that for both S. pastorianus 1 and S. pastorianus 2 strains, the production of acetic acid was zero in cold condition and really low (0.09 g/l) for classic condition regarding S. pastorianus 1. As a consequence, Saccharomyces pastorianus seems to be highly interesting for winemaking, alone or in co-inoculation with S. bayanus.

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