Chinese Fuzhuan brick-tea is a unique microbial fermented tea characterized by a period of fungal growth during its manufacturing process. The aim of the present study was to characterize, both ...physicochemically and microbiologically, traditional industrial production processes of Fuzhuan brick-tea. Fermenting tea samples were collected from the largest manufacturer. Physicochemical analyses showed that the low water content in the tea substrates provided optimal growth conditions for xerophilic fungi. The fungal communities existing in tea materials, fermenting tea, and stored teas were monitored by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) targeting the D1 region of the 26
S rRNA genes, followed by sequencing of the amplicons. Results revealed that the microorganisms were from, or closely related to, the genera
Eurotium, Debaryomyces,
Aspergillus,
Verticillium,
Pichia,
Pestalotiopsis,
Rhizomucor and
Beauveria. This is the first report of
Debaryomyces participating in the processing of Fuzhuan brick-tea. We concluded that the dominant genera
Eurotium, Debaryomyces and
Aspergillus are beneficial fungi associated with the fermentation of Fuzhuan brick-tea. The genus
Beauveria was present in the stored Fuzhuan brick-tea, which may help protect tea products from insect spoilage. The remaining four genera were of minor importance in the manufacturing of Fuzhuan brick-tea. The predominant
Eurotium species, a strain named
Eurotium sp. FZ, was phenotypically and genotypically identified as
Eurotium cristatum. High performance thin layer chromatography analysis of anthraquinones showed that emodin existed in all the dark tea samples, but physcion was only detectable in the tea fermented by
E. cristatum. The PCR-DGGE approach was an effective and convenient means for profiling the fungal communities in Fuzhuan brick-tea. These results may help promote the use of microbial consortia as starter cultures to stabilize and improve the quality of Fuzhuan brick-tea products.
► Eight genera of fungi were detected in Fuzhuan brick-tea processing by PCR-DGGE. ► A fungi isolate was phenotypically and genotypically identified as
E. cristatum. ► Emodin and physcion are major anthraquinones in dark teas by HPTLC.
Debaryomyces hansenii
comes of age as a new potential probiotic for terrestrial and aquatic animals. Probiotic properties, including inmunostimulatory effects, gut microbiota modulation, enhanced ...cell proliferation and differentiation, and digestive function improvements have been related to the oral delivery of
D. hansenii
. Its functional compounds, such as cell wall components and polyamines, have been identified and implicated in its immunomodulatory activity. In addition, in vitro studies using immune cells have shown standpoints on the possible recognition, regulation, and effector immune mechanisms stimulated by this yeast. This review describes historic, cutting-edge research findings, implications, and perspectives on the use of
D. hansenii
as a promising probiotic for animals.
Key points
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Debaryomyces hansenii has probiotic effects in terrestrial and aquatic animals.
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Nutritional effects could be associated to probiotic D. hansenii strains.
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β-D-Glucan and polyamines from D. hansenii are associated to probiotic properties.
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Adoption by the industry is expected in the next years.
The halophilic yeast
Debaryomyces hansenii
has been studied for several decades, serving as eukaryotic model for understanding salt and osmotic tolerance. Nevertheless, lack of consensus among ...different studies is found and, sometimes, contradictory information derived from studies performed in very diverse conditions. These two factors hampered its establishment as the key biotechnological player that was called to be in the past decade. On top of that, very limited (often deficient) engineering tools are available for this yeast. Fortunately
Debaryomyces
is again gaining momentum and recent advances using highly instrumented lab scale bioreactors, together with advanced –omics and HT-robotics, have revealed a new set of interesting results. Those forecast a very promising future for
D. hansenii
in the era of the so-called green biotechnology. Moreover, novel genetic tools enabling precise gene editing on this yeast are now available. In this review, we highlight the most recent developments, which include the identification of a novel gene implicated in salt tolerance, a newly proposed survival mechanism for
D. hansenii
at very high salt and limiting nutrient concentrations, and its utilization as production host in biotechnological processes.
Microbial antagonists provide a new perspective on biological control by altering microbial diversity to control postharvest diseases of fruit. In this study, the biological control effect of ...Debaryomyces hansenii on postharvest diseases of strawberry and the influence on strawberry quality were determined. At the same time, the effect of D. hansenii on the composition of surface microbiome of strawberry fruit was analyzed by high-throughput sequencing technology. The results showed that D. hansenii treatment can inhibit the natural decay rate of strawberries, and the treatment group maintained a higher ascorbic acid content than the control group. However, there was no difference between the control and treatment groups in firmness, weight loss rate, soluble solids, titratable acidity, and other quality indicators. On the surface of strawberries treated with D. hansenii, the diversity of fungal community was changed, the composition and structure of the community were also altered (except the abundance of Debaryomyces spp.). Strawberries treated with D. hansenii could alter bacterial and fungal populations, inhibit plant pathogens, and lower the frequency of postharvest diseases in strawberries. This study helps to understand the microbial community structure on the surface of strawberries and guides the synthesis of strawberry postharvest disease complex biocontrol strains to achieve stable and sustainable postharvest disease control strategies of the fruits.
•Debaryomyces hansenii reduced the natural decay rate of strawberries.•The surface microbiome of D. hansenii treated-strawberries was investigated.•D. hansenii treatment inhibited Erwinia and Cladosporium at the genus level.•The fungal community diversity of D. hansenii was changed.
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•Lactobacillus was the most predominant bacterial genus in both Suansun and Suancai.•Kazachstania and Debaryomyces were dominant in both Suansun and Suancai.•Pichia and ...Zygosaccharomyces were the other two major fungal genera in Suansun.•Nakaseomyces was another major fungal genus in Suancai.•Salinity was the most important physicochemical factor affecting microbial profiles.
Guangxi Suansun (Guangxi SS) and Guangxi Suancai (Guangxi SC) are two kinds of traditionally fermented vegetables consumed as cooking ingredients in Guangxi Province, China, for thousands of years. However, little is known about their microbial communities as well as the differences between them. Thus, this study was aimed to investigate and compare the physicochemical indexes as well as the bacterial and fungal profiles of Guangxi SS and Guangxi SC. Results showed that the titratable acidity, lactic acid and acetic acid content in SS were significantly higher than those in SC, while the salinity of SS was significantly lower than that in SC, and the nitrite contents in all samples were are far lower than the limit of nitrite contents in fermented vegetables. Firmicutes, Proteobacteria, Ascomycota and Basidiomycota were the main phyla observed in both SS and SC samples. Lactobacillus, Serratia, Stenotrophomonas and Lactococcus were the major bacterial genera in both SS and SC samples, the predominant fungal genera in SS group were Kazachstania, Debaryomyces and Pichia, while the major genera in SC group were Kazachstania, Debaryomyces and Nakaseomyces. At the species level, Lactobacillus acetotolerans, Pichia kudriavzevii, Debaryomyces hansenii, Pichia norvegensis, Kazachstania exigua and Kazachstania humilis were the major species observed in SS, while L. delbrueckii, L. fermentum, L. aviarius, and Pichia kudriavzevii and Debaryomyces hansenii were the predominant species in SC. Salinity was found to be more strongly correlated to the bacterial and fungal communities of both SS and SC than other physicochemical factors (pH, the titratable acidity, lactic acid and acetic acid content). This study provided detailed insight into the microbial communities of Guangxi SS and Guangxi SC, and the findings may help understand the microbial structures of Chinese traditional fermented vegetables.
Yeasts provide attractive host/vector systems for heterologous gene expression. The currently used yeast-based expression platforms include mesophilic and thermotolerant species. A eukaryotic ...expression system working at low temperatures could be particularly useful for the production of thermolabile proteins and proteins that tend to form insoluble aggregates. For this purpose, an expression system based on an Antarctic psychrotolerant yeast Debaryomyces macquariensis strain D50 that is capable of growing at temperatures ranging from 0 to 30 °C has been developed. The optimal physical culture conditions for D. macquariensis D50 in a fermenter are as follows: temperature 20 °C, pH 5.5, aeration rate of 1.5 vvm, and a stirring speed of 300 rpm. Four integrative plasmid vectors equipped with an expression cassette containing the constitutive GAP promoter and CYC1 transcriptional terminator from D. macquariensis D50 were constructed and used to clone and express a gene-encoding cold-active β-d-galactosidase of Paracoccus sp. 32d. The yield was 1150 U/L of recombinant yeast culture. Recombinant D. macquariensis D50 strains were mitotically stable under both selective and non-selective conditions. The D. macquariensis D50 host/vector system has been successfully utilized for the synthesis of heterologous thermolabile protein, and it can be an alternative to other microbial expression systems.
Arabitol is a low-calorie sugar alcohol with anti-cariogenic properties. Enzymatic hydrolysate of soybean flour is a new renewable biorefinery feedstock containing hexose, pentose, and organic ...nitrogen sources. Arabitol production by
Debaryomyces hansenii
using soybean flour hydrolysate was investigated. Effects of medium composition, operating conditions, and culture stage (growing or stationary phase) were studied. Production was also compared at different culture volumes to understand the effect of dissolved oxygen concentration (DO). Main factors examined for medium composition effects were the carbon to nitrogen concentration ratio (C/N), inorganic (ammonium) to organic nitrogen ratio (I/O-N), and sugar composition. Arabitol yield increased with increasing C/N ratio and a high I/O-N (0.8–1.0), suggesting higher yield at stationary phase of low pH (3.5–4.5). Catabolite repression was observed, with the following order of consumption: glucose > fructose > galactose > xylose > arabinose. Arabitol production also favored hexoses and, among hexoses, glucose. DO condition was of critical importance to arabitol production and cell metabolism. The yeast consumed pentoses (xylose and arabinose) only at more favorable DO conditions. Finally, arabitol was produced in fermentors using mixed hydrolysates of soy flour and hulls. The process gave an arabitol yield of 54%, volumetric productivity of 0.90 g/L-h, and specific productivity of 0.031 g/g-h.
Anthracnose is presently recognized as one of the most important postharvest disease of mango worldwide. To control the disease, chemical fungicides for a long time was widely used among fruit ...farmers, but recently found that pathogen had developed increasingly resistance to it. With people's growing desire of healthy and green food, finding new and environmentally friendly biological control approach was very necessary. In this paper, we provided a kind of new antagonistic yeast which enriched the strain resources and the efficacy of Debaryomyces nepalensis against postharvest anthracnose of mango fruit and the influence on quality parameters were investigated. The results showed that the decay incidence and lesion diameter of postharvest anthracnose of mango treated by D. nepalensis were significantly reduced compared with the control fruit stored at 25 °C for 30 d or at 15 °C for 40 d, and the higher concentration of D. nepalensis was, the better the efficacy of the biocontrol was. Study also found that 1 h was the best treatment duration and antagonistic yeast inoculated earlier had good biocontrol effect on anthracnose. Meanwhile, treatment by D. nepalensis could significantly reduce postharvest anthracnose of mango, delay the decrease in firmness, TSS, TA, and ascorbic acid value, and do not impair surface color during postharvest storage. Moreover, the increase in MDA (malondialdehyde) content and increase in cell membrane permeability of fruit treated by D. nepalensis was highly inhibited. The results suggested D. nepalensis treatment could not only maintain storage quality of mango fruit, but also decrease the decay incidence to anthracnose disease. All these results indicated that D. nepalensis has great potential for development of commercial formulations to control postharvest pathogens of mango fruit.
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•The chemical and metabolic properties of LPWs by different methods were determined.•Amino acids, phenylpropanoids, and flavonols were different among groups.•17 different metabolites ...were enriched from the highest different expressed pathways.•The SRA method stimulated the tyrosine and imparted a distinctive saucy aroma to the wine samples.
This study aimed to examine the effect of fermentation methods on the quality of Lycium barbarum and Polygonatum cyrtonema compound wine (LPW) by combining non-targeted metabolomic approaches with chemometrics and path profiling to determine the chemical and metabolic properties of LPW. The results demonstrated that SRA had higher leaching rates of total phenols and flavonoids, reaching 4.20 ± 0.10 v/v ethanol concentration. According to LC-MS non-targeting genomics, the metabolic profiles of LPW prepared by different mixtures of fermentation methods (Saccharomyces cerevisiae RW; Debaryomyces hansenii AS2.45) of yeast differed significantly. Amino acids, phenylpropanoids, flavonols, etc., were identified as the differential metabolites between different comparison groups. The pathways of tyrosine metabolism, biosynthesis of phenylpropanoids, and metabolism of 2-oxocarboxylic acids enriched 17 distinct metabolites. SRA stimulated the production of tyrosine and imparted a distinctive saucy aroma to the wine samples, providing a novel research concept for the microbial fermentation-based production of tyrosine.
