Isolation and identification of Starmerella davenportii strain Do18 and its application in black tea beverage fermentation

Revealing the comprehensive effect of mechanization on sauce-flavor Daqu through high-throughput sequencing and multi-dimensional metabolite profiling

Mechanization has emerged as a focal point in the modernization of traditional enterprises, offering standardized production and labor reduction benefits. However, little is known about how mechanization affects the microbiota and metabolite profiles of Daqu. To address this gap, we conducted a comprehensive comparison between traditional and mechanical sauce-flavor Daqu using a multi-omics approach. Results showed that mechanical Daqu exhibited higher acidity, amino acid nitrogen and enzyme activity, alongside lower fat and moisture levels. Following mechanization, lactic acid bacteria (LAB), Staphylococcus, Aspergillus and Saccharomycopsis were enriched and identified as biomarkers, whereas Oceanobacillus, Monascus and Scopulariopsis were notably decreased. Furthermore, significant disparities in metabolic profiles were observed between the two types of Daqu based on GC-MS, GC-IMS, and LC-MS/MS analyses. The content of volatile compounds was significantly higher in mechanical Daqu (332.82 ± 22.69 mg/kg), while that of non-volatile compounds was higher in traditional Daqu (753.44 ± 41.82 mg/kg). Moreover, OPLS-DA models identified 44 volatile and 31 non-volatile compounds as differential metabolites. Multivariate statistical analysis indicated that bacteria and fungi primarily contributed to protease and saccharification activities, respectively. Additionally, the co-occurrence network revealed that Oceanobacillus and Scopulariopsis were closely associated with non-volatile compound formation, while LAB and Rhizopus significantly influenced volatile compound production. These findings elucidate the multi-dimensional relationship between mechanization and Daqu quality, offering insights to advance the modernization of traditional industries.

Sensory evaluation and chemical composition of Solanum nigrum and Solanum torvum herbal tea and spice

Herbal teas are ingested for various purposes and by diverse populations across the globe. There is a growing recognition among individuals of the advantages associated with the use of this beverage, leading to a heightened demand for the manufacture of herbal tea derived from therapeutic plants. Spices on the other hand add flavour to food but could pose harm if it is high in phytates and oxalates. The objective of this study was to develop natural spices and herbal tea with health beneficial properties using Solanum nigrum and Solanum torvum berries. Herbal tea samples from S. nigrum were prepared by sorting berries, maceration, divided into two (fermenting at 18 °C and non-fermenting) and dried at 60 °C for 12 h in a hot oven. Spices from S. torvum and S. nigrum were prepared by removing the berries from the stalk, freeze-drying and smooth milling into fine powder. In addition, antinutrient, phytochemical and sensory evaluation studies were conducted on these spices and herbal teas. A nine-point hedonic scale was utilized for the purpose of conducting a consumer acceptability sensory evaluation test using 101 untrained panelists. Data was then analyzed by t-test, one-way analysis of variance (ANOVA) and the level of significance (p < 0.05) was assessed using Tukey's and Dunnett's multiple comparison tests. The panellists expressed a favourable perception towards Solanum nigrum unripe unfermented green herbal tea (6.65 ± 2.08) as compared to the other formulated teas due to the components working together in a way that produces a nice tea sample. Both Solanum nigrum and Solanum torvum spices contained various levels of catechins, saponins, flavonoids, oxalates, phytates and tannins comparable to literature. The herbal tea samples exhibited a range of catechin content, varying from 0.255 to 0.756 mg/g. The antioxidant activity of the various herbal tea samples ranged from 66.37 ± 0.24 to 78.53 ± 0.18 µg/mL GAE as determined by the DPPH free radical assay Fermented black herbal teas recorded higher total phenols (2.80 ± 0.09d), total flavonoids (21.84 ± 1.84c) and showed greater antioxidant activity (78.53 ± 0.18a) as compared to the unfermented green herbal teas. The process of fermentation resulted in a decrease in pH from 7.22 to 6.53 within a period of 12 h. The Total Titratable Acidity (TTA) grew as the fermentation period progressed, whereas the Total Soluble Solids (TSS) decreased. Phytates were the least antinutrients among the two Solanum species accounting for 0.02 mg/100 g and 0.03 mg/100 g in S. torvum berries (STBs) and (S. nigrum berries) SNBs respectively.

Microbiological, Functional, and Chemico-Physical Characterization of Artisanal Kombucha: An Interesting Reservoir of Microbial Diversity

Kombucha is a trending tea fermented via a complex microflora of yeasts and acetic acid bacteria. It can be a valid low-calorie substitute for soft drinks due to its sour, naturally carbonated, and sweet taste. Despite increased interest, the microflora and functional properties of kombucha have not yet been fully understood. The aim of this work was to characterize, from a microbiological, chemico-physical, and functional point of view, three types of artisanal kombucha obtained by fermenting green tea containing sugar by means of different starter cultures. Metagenomic analysis revealed a predominance of yeasts compared to bacteria, regardless of the sample. In particular, Brettanomyces spp. was found to be the dominant yeast. Moreover, the different types of kombucha had different microbial patterns in terms of acetic acid bacteria and yeasts. Ethanol and acetic acid were the dominant volatile molecules of the kombucha volatilome; the samples differed from each other in terms of their content of alcohols, esters, and acids. All the samples showed a high antioxidant potential linked to the high content of phenols. This study confirmed the positive chemico-physical and functional properties of kombucha and indicated that the microflora responsible for the fermentation process can significantly affect the characteristics of the final product.

Comparing the differences of physicochemical properties and volatiles in semi-dry Hakka rice wine and traditional sweet rice wine via HPLC, GC-MS and E-tongue analysis

This study aimed to explore effects of indica rice addition, rice soaking time and rice soup addition on total sugar and alcohol content of semi-dry Hakka rice wine (HRW) and compare its difference in physicochemical properties and volatiles with traditional sweet rice wine (TSRW) via HPLC, GC-MS and E-tongue. The optimal fermentation conditions of semi-dry HRW were 50 % indica rice addition, 12 h rice soaking time and 85 % rice soup addition. The total sugar (16.13 mg/mL) of semi-dry HRW was significantly lower than that of TSRW (135.79 mg/mL), especially the trehalose, glucose, sucrose and maltose. Its alcohol content was significantly higher than that of TSRW. There were significant differences in volatile components between semi-dry HRW and TSRW, especially esters, alcohols and ketones, but no significant differences in organic acids and amino acids. Results obtained could provide reference data for improving the fermentation process and quality of semi-dry HRW.

Kombucha: Challenges for Health and Mental Health

BACKGROUND

Increasing research into probiotics is showing potential benefits for health in general and mental health in particular. Kombucha is a recent beverage and can be considered a probiotic drink, but little is known about its effects on physical and mental health. This product is experiencing growth in the market; however, there are no scientific results to support its potential for physical and mental health.

AIM

This review article aims to draw attention to this issue and to highlight the lack of studies in this area.

KEY FINDINGS AND CONCLUSIONS

The lack of legislation for the correct marketing of this product may also constrain clinical studies. However, clinical studies are of utmost importance for an in-depth understanding of the effects of this product on the human body. More research is needed, not only to better understand the impact of Kombucha on the human body, but also to ensure the application of regulatory guidelines for its production and marketing and enable its safe and effective consumption.

Dissecting the role of microorganisms in tea production of different fermentation levels: a multifaceted review of their action mechanisms, quality attributes and future perspectives

Tea is one of the most popular beverages worldwide, with several health benefits attributed for its rich chemical composition and further associated with fermentation process to improve its quality attributes. Most tea types originate from the leaves of Camellia sinensis with differences in fermentation levels yielding black tea, green tea, pouchong tea, oolong tea. Teas like pu-erh or kombucha to encompass both green and red types are further post-fermented. Tea fermentation is a traditional process involving physical, biochemical, and microbial changes which are associated with improved organoleptic characters, nutritive value, and health outcomes. The production of fermented tea relies on naturally occurring enzymes and microbial metabolic activities. This review focuses on presenting a holistic overview on the effect of different microorganisms including bacteria, yeast, and fungi on the biochemical changes and sensory attributes of fermented tea products reported in research articles along the last 15 years. Moreover, production conditions and major biochemical changes are dissected to present the best factors influencing fermented tea quality. This review presents an evidence-based reference for specialists in tea industry to optimize tea fermentation process for targeted attributes.

Modulation effects of microorganisms on tea in fermentation

Tea is a popular traditional drink and has been reported to exhibit various health-promoting effects because of its abundance of polyphenols. Among all the tea products, fermented tea accounts for the majority of tea consumption worldwide. Microbiota plays an important role in the fermentation of tea, which involves a series of reactions that modify the chemical constituents and thereby affect the flavor and bioactivities of tea. In the present review, the microorganisms involved in fermented tea and tea extracts in the recent studies were summarized and the modulation effects of microorganisms on tea in fermentation, including polyphenols composition and content, biological activities and sensory characteristics, were also critically reviewed. It is expected that the data summarized could provide some references for the development of microbial fermented tea drinks with specific nutrition and health benefits.

The investigation on the characteristic metabolites of Lactobacillus plantarum RLL68 during fermentation of beverage from by-products of black tea manufacture

At present, lactic acid bacteria (LAB) fermentation is commonly considered as an effective strategy to remarkably drive the improvement of flavor and nutritional value, and extend shelf-life of fermented foods. In this study, the by-product of tea manufacture, including broken tea segments and tea stalk, was used to produce fermented tea beverages. In addition, the residual components of matrices and bacterial metabolites were measured, as well as the sensory quality of the beverage was evaluated. Subsequently, the determination of monosaccharides, volatile aroma profile, free amino acids, biogenic amines and organic acids, and several functional substances involving γ-aminobutyric acid (GABA), polyphenols, caffeine and L-theanine were carried out. The results revealed that glucose, fructose, mannose and xylose are principal carbon source of Lactobacillus plantarum RLL68 during the fermentation; moreover, the abundance of aromatic substances is varied dramatically and the characteristic flavors of the beverages, particularly fermentation for 48 h and 72 h, are imparted with sweet and fruity odor on the basis of initial nutty and floral odor; Meanwhile, the organoleptic qualities of fermented beverages is also enhanced. Furthermore, the levels of organic acids and GABA are elevated, while the bitter amino acids, as well as some bioactive substances including tea polyphenols and L-theanine are declined; Besides, the caffeine level almost remains constant, and quite low levels of various biogenic amines are also observed. The results of this study will provide the theoretical basis to steer and control the flavor and quality of the fermented tea beverages in the future.

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The dynamic variation of characteristic metabolites of the beverage was elucidated.

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The characteristic flavors changed from nutty and floral to sweet and fruity.

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L. plantarum fermentation bring both beneficial and adverse impacts.

Microbial Diversity and Characteristics of Kombucha as Revealed by Metagenomic and Physicochemical Analysis

Kombucha is a fermented tea made from a Symbiotic Culture of Bacteria and Yeast (SCOBY) with a long history of use as a health tonic. It is likely that most health benefits come from the tea and fermentation metabolites from specific microbial communities. Despite its growing importance as a functional health drink, the microbial ecosystem present in kombucha has not been fully documented. To characterize the microbial composition and biochemical properties of 'The Good Brew' original base kombucha, we used metagenomics amplicon (16S rRNA and ITS) sequencing to identify the microbial communities at the taxonomic level. We identified 34 genera with 200 microbial species yet described in kombucha. The dominance of organic acid producing microorganisms Acetobacter, Komagataeibacter and Starmerella are healthy for the human gut and their glucose metabolising activities have a putative role in preventing conditions such as diabetes and obesity. Kombucha contains high protein (3.31 µg/mL), high phenolic content (290.4 mg/100 mL) and low sugars (glucose: 1.87 g/L; sucrose 1.11 g/L; fructose: 0.05 g/L) as compared to green tea. The broad microbial diversity with proven health benefits for the human gut suggests kombucha is a powerful probiotic. These findings are important to improve the commercial value of kombucha and uncover the immense prospects for health benefits.

Metabolome Exploration by High-Resolution Mass Spectrometry Methodologies of Two New Yeast Species: Starmerella reginensis and Starmerella kourouensis

Nature is harnessed since ancient times to fulfill human needs, and yeast culture has been mastered for bakery, brewery, or the preparation of beverages. In this context, the two recently discovered yeast species Starmerella reginensis and Starmerella kourouensis, belonging to a genus related to fermentative activities in the literature, were explored via untargeted metabolomics approaches. Ultrahigh-performance liquid chromatography hyphenated with tandem mass spectrometry and a deep investigation of molecular networks and spectral data allowed the annotation of, respectively, 439 and 513 metabolites for S. reginensis and S. kourouensis, with approximatively 30% compound annotations and 40% chemical class annotations for both yeast strains. These analyses and Fourier transform ion cyclotron resonance mass spectrometry accurate metabolic profiles unveiled a rich content of alkaloids, lipids, amino acids, and terpenoids for S. reginensis. S. kourouensis presents a similar profile with more sulfated compounds. In short, these results enrich the current knowledge about Starmerella yeast secondary metabolites and reveal their significant structural diversity of small molecules.

Microbial Composition of SCOBY Starter Cultures Used by Commercial Kombucha Brewers in North America

Kombucha fermentation is initiated by transferring a solid-phase cellulosic pellicle into sweetened tea and allowing the microbes that it contains to initiate the fermentation. This pellicle, commonly referred to as a symbiotic culture of bacteria and yeast (SCOBY), floats to the surface of the fermenting tea and represents an interphase environment, where embedded microbes gain access to oxygen as well as nutrients in the tea. To date, various yeast and bacteria have been reported to exist within the SCOBY, with little consensus as to which species are essential and which are incidental to Kombucha production. In this study, we used high-throughput sequencing approaches to evaluate spatial homogeneity within a single commercial SCOBY and taxonomic diversity across a large number (n = 103) of SCOBY used by Kombucha brewers, predominantly in North America. Our results show that the most prevalent and abundant SCOBY taxa were the yeast genus Brettanomyces and the bacterial genus Komagataeibacter, through careful sampling of upper and lower SCOBY layers. This sampling procedure is critical to avoid over-representation of lactic acid bacteria. K-means clustering was used on metabarcoding data of all 103 SCOBY, delineating four SCOBY archetypes based upon differences in their microbial community structures. Fungal genera Zygosaccharomyces, Lachancea and Starmerella were identified as the major compensatory taxa for SCOBY with lower relative abundance of Brettanomyces. Interestingly, while Lactobacillacae was the major compensatory taxa where Komagataeibacter abundance was lower, phylogenic heat-tree analysis infers a possible antagonistic relationship between Starmerella and the acetic acid bacterium. Our results provide the basis for further investigation of how SCOBY archetype affects Kombucha fermentation, and fundamental studies of microbial community assembly in an interphase environment.