Exploring the impact of magnetic fields on biomass production efficiency under aerobic and anaerobic batch fermentation of Saccharomyces cerevisiae.

In this work, the effect of moderate electromagnetic fields (2.5, 10, and 15 mT) was studied using an immersed coil inserted directly into a bioreactor on batch cultivation of yeast under both aerobic and anaerobic conditions. Throughout the cultivation, parameters, including CO2 levels, O2 saturation, nitrogen consumption, glucose uptake, ethanol production, and yeast growth (using OD 600 measurements at 1-h intervals), were analysed. The results showed that 10 and 15 mT magnetic fields not only statistically significantly boosted and sped up biomass production (by 38-70%), but also accelerated overall metabolism, accelerating glucose, oxygen, and nitrogen consumption, by 1-2 h. The carbon balance analysis revealed an acceleration in ethanol and glycerol production, albeit with final concentrations by 22-28% lower, with a more pronounced effect in aerobic cultivation. These findings suggest that magnetic fields shift the metabolic balance toward biomass formation rather than ethanol production, showcasing their potential to modulate yeast metabolism. Considering coil heating, opting for the 10 mT magnetic field is preferable due to its lower heat generation. In these terms, we propose that magnetic field can be used as novel tool to increase biomass yield and accelerate yeast metabolism.

Metabolomic analysis reveals Ligilactobacillus salivarius CCFM 1266 fermentation improves dairy product quality.

Previous studies have demonstrated that Ligilactobacillus salivarius CCFM 1266 exhibits anti-inflammatory properties and the capability to synthesize niacin. This study aimed to investigate the fermentative abilities of L. salivarius CCFM 1266 in fermented milk. Metabonomic analysis revealed that fermentation by L. salivarius CCFM 1266 altered volatile flavor compounds and metabolite profiles, including heptanal, nonanal, and increased niacin production. Genomic investigations confirmed that L. salivarius CCFM 1266 possess essential genes for the metabolism of fructose and mannose, affirming its proficiency in utilizing fructooligosaccharides and mannan oligosaccharides. The addition of fructooligosaccharides and mannan oligosaccharides during the fermentation process significantly facilitated the proliferation of L. salivarius CCFM 1266 in fermented milk, with growth exceeding 107 colony-forming units (CFU)/mL. This intervention not only augmented the microbial density but also modified the metabolite composition of fermented milk, resulting in an elevated presence of advantageous flavor compounds such as nonanal, 2,3-pentanedione, and 3-methyl-2-butanone. However, its influence on improving the texture of fermented milk was observed to be minimal. Co-fermentation of L. salivarius CCFM 1266 with commercial fermentation starters indicated that L. salivarius CCFM 1266 was compatible, similarly altering metabolite composition and increasing niacin content in fermented milk. In summary, the findings suggest that L. salivarius CCFM 1266 holds substantial promise as an adjunctive fermentation starter, capable of enhancing the nutritional diversity of fermented milk products.

Pectin forms polymeric pigments by complexing anthocyanins during red winemaking and ageing.

The long-term stability of red wine color depends on the formation of polymeric pigments from anthocyanins. Although there is still a lot of uncertainty about the specific structure of this diverse group of pigments, there is consensus that they are reaction products of anthocyanins and other polyphenols. Interactions between anthocyanins and pectic polysaccharides have been suggested to stabilize anthocyanins. This study explores the impact of such interactions by adding pectin during red winemaking. The results demonstrate that these interactions induce the formation of additional polymeric pigments which enhance the pigment stability during fermentation and aging. While initial pigment formation is higher in wines with added pectin, a notable proportion of the complexes degrades in the later stages of fermentation. Presumably, tannins form insoluble complexes with pectin, reducing tannin concentration by more than 300 mg/L. Anthocyanin concentrations decrease by over 400 mg/L, and polymeric pigments double. Anthocyanins that form polymeric pigments with pectic polysaccharides expand the range of pigments in red wines with possible consequences for the sensory properties of the wine. These findings highlight the complex interactions between pectin, anthocyanins, and tannins, and their influence on pigment formation and wine composition during fermentation and aging.

Effects of seasonal harvest of kimchi cabbage on microbial and metabolic profiles of kimchi.

Kimchi cabbage, the key ingredient in kimchi, is cultivated year-round to meet high production demands. This study aimed to examine the effects of seasonal harvesting (spring, summer, fall, and winter) on the microbial and metabolic profiles of kimchi during 30 days of fermentation. Lactic acid bacteria distribution is notably influenced by seasonal variations, with Latilactobacillus dominant in fall-harvested kimchi group and Weissella prevailing in spring, summer, and winter. The microbial communities of spring and fall group exhibited similar profiles before fermentation, whereas the microbial communities and metabolic profiles of spring and summer group were similar after 30 days of fermentation. Seasonal disparities in metabolite concentrations, including glutamic acid, serine, and cytosine, persist throughout fermentation. This study provides a comprehensive understanding of the substantial impact of seasonal harvesting of kimchi cabbage on the microbial and metabolic characteristics of kimchi, providing valuable insights into producing kimchi with diverse qualities.

Lacto-fermented garlic handcrafted in the Lower Silesia Region (Poland): Microbial diversity, morpho-textural traits, and volatile compounds.

The aim of the present study was to provide a first characterization of lacto-fermented garlic manufactured by local small-scale artisanal producers in the Lower Silesia Region (Poland). The lacto-fermented garlic samples showed high nutritional features in terms of antioxidant activity. A total of 86 compounds, belonging to various chemical classes, were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC/MS). Most of these compounds belonged to six main classes, being sulfur compounds, esters and acetates, oxygenated monoterpenes, monoterpene hydrocarbons, and alcohols. Aldehydes, acids, ketones, furans, and phenols were also identified. In the analyzed samples, counts up to 8 log cfu g-1 were observed for lactic acid bacteria. Metataxonomic analysis revealed the presence of Levilactobacillus, Lactiplantibacillus, Latilactobacillus, Secundilactobacillus, Weissella, Leuconostoc, Lactococcus, Pediococcus, and Lacticaseibacillus among the major taxa. These results were confirmed by the isolation and characterization of viable lactic acid bacteria. Indeed, the presence of the closest relatives to Lacticaseibacillus casei group, Pediococcus parvulus, Levilactobacillus brevis, Levilactobacillus parabrevis, and Lactiplantibacillus plantarum group was observed. A good acidification performance in salty garlic-based medium was observed for all the isolates that, between 8 and 15 days of fermentation, reached pH values comprised between 4 and 3.5, depending on the tested species. Of note, 15 out of the 37 lactic acid bacteria isolates (Levilactobacillus parabrevis, Pediococcus parvulus, Lactiplantibacillus plantarum group, and Lacticaseibacillus casei group) showed the presence of the hdcA gene of Gram-positive bacteria encoding for histidine decarboxylase. Furthermore, for 8 out of the 37 isolates the in-vitro exopolysaccharides production was observed. No isolate showed inhibitory activity against the three Listeria innocua strains used as surrogate for Listeria monocytogenes.

Probiotic Potential and Application of Indigenous Non-Starter Lactic Acid Bacteria in Ripened Short-Aged Cheese.

There are massive sources of lactic acid bacteria (LAB) in traditional dairy products. Some of these indigenous strains could be novel probiotics with applications in human health and supply the growing needs of the probiotic industry. In this work, were analyzed the probiotic and technological properties of three Lactobacilli strains isolated from traditional Brazilian cheeses. In vitro tests showed that the three strains are safe and have probiotic features. They presented antimicrobial activity against pathogenic bacteria, auto-aggregation values around 60%, high biofilm formation properties, and a survivor of more than 65% to simulated acid conditions and more than 100% to bile salts. The three strains were used as adjunct cultures separately in a pilot-scale production of Prato cheese. After 45 days of ripening, the lactobacilli counts in the cheeses were close to 8 Log CFU/g, and was observed a reduction in the lactococci counts (around -3 Log CFU/g) in a strain-dependent manner. Cheese primary and secondary proteolysis were unaffected by the probiotic candidates during the ripening, and the strains showed no lipolytic effect, as no changes in the fatty acid profile of cheeses were observed. Thus, our findings suggest that the three strains evaluated have probiotic properties and have potential as adjunct non-starter lactic acid bacteria (NSLAB) to improve the quality and functionality of short-aged cheeses.

Metagenomic and flavoromic profiling reveals the correlation between the microorganisms and volatile flavor compounds in Monascus-fermented cheese.

The Monascus-fermented cheese (MC) is a unique cheese product that undergoes multi-strain fermentation, imparting it with distinct flavor qualities. To clarify the role of microorganisms in the formation of flavor in MC, this study employed SPME (arrow)-GC-MS, GC-O integrated with PLS-DA to investigate variations in cheese flavors represented by volatile flavor compounds across 90-day ripening periods. Metagenomic datasets were utilized to identify taxonomic and functional changes in the microorganisms. The results showed a total of 26 characteristic flavor compounds in MC at different ripening periods (VIP＞1, p < 0.05), including butanoic acid, hexanoic acid, butanoic acid ethyl ester, hexanoic acid butyl ester, 2-heptanone and 2-octanone. According to NR database annotation, the genera Monascus, Lactococcus, Aspergillus, Lactiplantibacillus, Staphylococcus, Flavobacterium, Bacillus, Clostridium, Meyerozyma, and Enterobacter were closely associated with flavor formation in MC. Ester compounds were linked to Monascus, Meyerozyma, Staphylococcus, Lactiplantibacillus, and Bacillus. Acid compounds were linked to Lactococcus, Lactobacillus, Staphylococcus, and Bacillus. The production of methyl ketones was closely related to the genera Monascus, Staphylococcus, Lactiplantibacillus, Lactococcus, Bacillus, and Flavobacterium. This study offers insights into the microorganisms of MC and its contribution to flavor development, thereby enriching our understanding of this fascinating dairy product.

Deciphering the core microbes and their interactions in spontaneous Baijiu fermentation: A comprehensive review.

The spontaneous Baijiu fermentation system harbors a complex microbiome that is highly dynamic in time and space and varies depending on the Jiuqu starters and environmental factors. The intricate microbiota presents in the fermentation environment is responsible for carrying out various reactions. These reactions necessitate the interaction among the core microbes to influence the community function, ultimately shaping the distinct Baijiu styles through the process of spontaneous fermentation. Numerous studies have been conducted to enhance our understanding of the diversity, succession, and function of microbial communities with the aim of improving fermentation manipulation. However, a comprehensive and critical assessment of the core microbes and their interaction remains one of the significant challenges in the Baijiu fermentation industry. This paper focuses on the fermentation properties of core microbes. We discuss the state of the art of microbial traceability, highlighting the crucial role of environmental and starter microbiota in the Baijiu brewing microbiome. Also, we discuss the various interactions between microbes in the Baijiu production system and propose a potential conceptual framework that involves constructing predictive network models to simplify and quantify microbial interactions using co-culture models. This approach offers effective strategies for understanding the core microbes and their interactions, thus beneficial for the management of microbiota and the regulation of interactions in Baijiu fermentation processes.

Effects of pickle brine and glycine addition on biogenic amine production in pickle fermentation.

This study investigated the effects of different pickle brines and glycine additions on biogenic amine formation in pickle fermentation. The results showed that the brines with higher biogenic amine content led to the production of more biogenic amines in the simulated pickle fermentation system. This was related to the abundance of biogenic amine-producing microorganisms in the microbial communities of the brines. Metagenome analysis of the brines and metatranscriptome analysis of the fermentation systems showed that putrescine was primarily from Lactobacillus, Oenococcus, and Pichia, while histamine and tyramine were primarily from Lactobacillus and Tetragenococcus. Addition of glycine significantly reduced the accumulation of biogenic amines in the simulated pickle fermentation system by as much as 70 %. The addition of glycine had no inhibitory effect on the amine-producing microorganisms, but it down-regulated the transcription levels of the genes for enzymes related to putrescine synthesis in Pichia, Lactobacillus, and Oenococcus, as well as the histidine decarboxylase genes in Lactobacillus and Tetragenococcus. Catalytic reaction assay using crude solutions of amino acid decarboxylase extracted from Lactobacillus brevis showed that the addition of glycine inhibited 45 %-55 % of ornithine decarboxylase and tyrosine decarboxylase activities. This study may provide a reference for the study and control of the mechanism of biogenic amine formation in pickle fermentation.

Differential effects of pectin-based dietary fibre type and gut microbiota composition on in vitro fermentation outcomes.

Interactions between human gut microbiota and dietary fibres (DF) are influenced by the complexity and diversity of both individual microbiota and sources of DF. Based on 480 in vitro fermentations, a full factorial experiment was performed with six faecal inocula representing two enterotypes and three DF sources with nanometer, micrometer, and millimeter length-scales (apple pectin, apple cell walls and apple particles) at two concentrations. Increasing DF size reduced substrate disappearance and fermentation rates but not biomass growth. Concentrated DF enhanced butyrate production and lactate cross-feeding. Enterotype differentiated final microbial compositions but not biomass or fermentation metabolite profiles. Individual donor microbiota differences did not influence DF type or concentration effects but were manifested in the promotion of different functional microbes within each population with the capacity to degrade the DF substrates. Overall, consistent effects (independent of donor microbiota variation) of DF type and concentration on kinetics of substrate degradation, microbial biomass production, gas kinetics and metabolite profiles were found, which can form the basis for informed design of DF for desired rates/sites and consequences of gut fermentation. These results add further evidence to the concept that, despite variations between individuals, the human gut microbiota represents a community with conserved emergent properties.

Glycerol-driven adaptive evolution for the production of low-molecular-weight Welan gum: Characterization and activity evaluation.

Through adaptive laboratory evolution (ALE) of Sphingomonas sp. ATCC 31555, fermentation for production of low-molecular-weight welan gum (LMW-WG) was performed using glycerol as sole carbon source. During ALE, GPC-MALS analysis revealed a gradual decrease in WG molecular weight with the increase of adaptation cycles, accompanied by changes in solution conformation. LMW-WG was purified and structurally analyzed using GPC-MALS, monosaccharide composition analysis, infrared spectroscopy, NMR analysis, atomic force microscopy, and scanning electron microscopy. Subsequently, LMW-WG obtains hydration, transparency, antioxidant activity, and rheological properties. Finally, an in vitro simulation colon reactor was used to evaluate potential prebiotic properties of LMW-WG as dietary fiber. Compared with WG produced using sucrose as substrate, LMW-WG exhibited a fourfold reduction in molecular weight while maintaining moderate viscosity. Structurally, L-Rha nearly completely replaced L-Man. Furthermore, LMW-WG demonstrated excellent hydration, antioxidant activity, and high transparency. It also exhibited resistance to saliva and gastrointestinal digestion, showcasing a favorable colonization effect on Bifidobacterium, making it a promising symbiotic agent.

Temporal and spatial dynamics within the fungal microbiome of grape fermentation.

Over 6 years, we conducted an extensive survey of spontaneous grape fermentations, examining 3105 fungal microbiomes across 14 distinct grape-growing regions. Our investigation into the biodiversity of these fermentations revealed that a small number of highly abundant genera form the core of the initial grape juice microbiome. Consistent with previous studies, we found that the region of origin had the most significant impact on microbial diversity patterns. We also discovered that certain taxa were consistently associated with specific geographical locations and grape varieties, although these taxa represented only a minor portion of the overall diversity in our dataset. Through unsupervised clustering and dimensionality reduction analysis, we identified three unique community types, each exhibiting variations in the abundance of key genera. When we projected these genera onto global branches, it suggested that microbiomes transition between these three broad community types. We further investigated the microbial community composition throughout the fermentation process. Our observations indicated that the initial microbial community composition could predict the diversity during the early stages of fermentation. Notably, Hanseniaspora uvarum emerged as the primary non-Saccharomyces species within this large collection of samples.

Comparative transcriptome analysis of doramectin-producing Streptomyces avermitilis N72 and its mutant strains.

Doramectin, an essential animal anthelmintic, is synthesized through the fermentation process of Streptomyces avermitilis. This study delves into the transcriptomic profiles of two strains, namely the doramectin-producing wild-type S. avermitilis N72 and its highly doramectin-producing mutant counterpart, S. avermitilis XY-62. Comparative analysis revealed 860 up-regulated genes and 762 down-regulated genes in the mutant strain, notably impacting the expression of key genes pivotal in doramectin biosynthesis, including aveA1, aveA2, aveA3, aveA4, aveE, and aveBI. These findings shed light on the molecular mechanisms underpinning the heightened doramectin production in S. avermitilis XY-62, presenting promising avenues for optimizing doramectin production processes.

Effects of community ecological network construction on physicochemical, microbial, and quality characteristics of inoculated northeast sauerkraut: A new insight in food fermentation processes.

The enhancement of the quality of northeast sauerkraut can be achieved by inoculation with lactic acid bacteria. However, a comprehensive ecological understanding of the intricate dynamic processes involved is currently lacking, which could yield valuable insights for regulating sauerkraut fermentation. This study compares spontaneously sauerkrauts with the sauerkrauts inoculated with autochthonous Lactiplantibacillus plantarum SC-MDJ and commercial L. plantarum, respectively. We examine their physicochemical properties, quality characteristics, bacterial community dynamics, and ecological network interactions. Inoculation with L. plantarum leads to reduced bacterial community richness and niche breadth, but an increase in robustness, interactions, and assembly processes. Notably, there appears to be a potential correlation between bacterial community structure and quality characteristics. Particularly, sauerkraut inoculated with L. plantarum SC-MDJ may produce a sourness more quickly, possibly attributed to the enhanced ecological role of L. plantarum SC-MDJ. This study establishes a foundation for the targeted regulation of sauerkraut fermentation.

Changes of microbial communities and metabolites in the fermentation of persimmon vinegar by bioaugmentation fermentation.

To evaluate the effects of bioaugmentation fermentation inoculated with one ester-producing strain (Wickerhamomyces anomalus ZX-1) and two strains of lactic acid bacteria (Lactobacillus plantarum CGMCC 24035 and Lactobacillus acidophilus R2) for improving the flavor of persimmon vinegar, microbial community, flavor compounds and metabolites were analyzed. The results of microbial diversity analysis showed that bioaugmentation fermentation significantly increased the abundance of Lactobacillus, Saccharomyces, Pichia and Wickerhamomyces, while the abundance of Acetobacter, Apiotrichum, Delftia, Komagataeibacter, Kregervanrija and Aspergillus significantly decreased. After bioaugmentation fermentation, the taste was softer, and the sensory irritancy of acetic acid was significantly reduced. The analysis of HS-SPME-GC-MS and untargeted metabolomics based on LC-MS/MS showed that the contents of citric acid, lactic acid, malic acid, ethyl lactate, methyl acetate, isocitrate, acetoin and 2,3-butanediol were significantly increased. By multivariate analysis, 33 differential metabolites were screened out to construct the correlation between the differential metabolites and microorganisms. Pearson correlation analysis showed that methyl acetate, ethyl lactate, betaine, aconitic acid, acetoin, 2,3-butanediol and isocitrate positively associated with Wickerhamomyces and Lactobacillus. The results confirmed that the quality of persimmon vinegar was improved by bioaugmentation fermentation.

Microbial dynamics and quality characteristics of spontaneously fermented salamis produced by replacing pork fat with avocado pulp.

The aim of this study was to develop a novel and healthier fermented meat product by replacing pork fat with avocado pulp (AVP) during salami production. Experimental salamis were produced under laboratory conditions by substituting pork fat with AVP partially (10-AVP) and totally (20-AVP), while control salamis (CTR) remained AVP-free. The microbial composition of control and experimental salamis was assessed using a combined culture-dependent and -independent approach. Over a 20-days ripening period, lactic acid bacteria, coagulase-negative staphylococci, and yeasts dominated the microbial community, with approximate levels of 9.0, 7.0 and 6.0 log CFU/g, respectively. Illumina technology identified 26 taxonomic groups, with leuconostocs being the predominant group across all trials [constituting 31.26-59.12 % of relative abundance (RA)]. Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed changes in fatty acid composition and volatile organic compounds due to the substitution of pork fat with AVP. Specifically, monounsaturated fatty acids and terpene compounds increased, while saturated fatty acids and lipid oxidation products decreased. Although AVP influenced the sensory characteristics of the salamis, the highest overall satisfaction ratings were observed for the 10-AVP salamis. Consequently, substituting pork fat with AVP emerges as a viable strategy for producing healthier salamis and diversifying the meat product portfolio.

Study of the effects of pasteurization and selected microbial starters on functional traits of fermented table olives.

Table olives are one of the most known fruit consumed as fermented food, being a fundamental component of the Mediterranean diet. Their production and consumption continue to increase globally and represent an important economic source for the producing countries. One of the most stimulating challenges for the future is the modernization of olive fermentation process. Besides the demand for more reproducible and safer production methods that could be able to reduce product losses and potential risks, producers and consumers are increasingly attracted by the final product characteristics and properties on human health. In this study, the contribution of microbial starters to table olives was fully described in terms of specific enzymatic and microbiological profiles, nutrient components, fermentation-derived compounds, and content of bioactive compounds. The use of microbial starters from different sources was tested considering their technological features and potential ability to improve the functional traits of fermented black table olives. For each fermentation assay, the effects of controlled temperature (kept at 20 °C constantly) versus not controlled environmental conditions (oscillating between 7 and 17 °C), as well as the consequences of the pasteurization treatment were tested on the final products. Starter-driven fermentation strategies seemed to increase both total phenolic content and total antioxidant activity. Herein, among all the tested microbial starters, we provide data indicating that two bacterial strains (Leuconostoc mesenteroides KT 5-1 and Lactiplantibacillus plantarum BC T3-35), and two yeast strains (Saccharomyces cerevisiae 10A and Debaryomyces hansenii A15-44) were the better ones related to enzyme activities, total phenolic content and antioxidant activity. We also demonstrated that the fermentation of black table olives under not controlled environmental temperature conditions was more promising than the controlled level of 20 °C constantly in terms of technological and functional properties considered in this study. Moreover, we confirmed that the pasteurization process had a role in enhancing the levels of antioxidant compounds.

Integrative metagenomics, volatilomics and chemometrics for deciphering the microbial structure and core metabolic network during Chinese rice wine (Huangjiu) fermentation in different regions.

Huangjiu is a spontaneously fermented alcoholic beverage, that undergoes intricate microbial compositional changes. This study aimed to unravel the flavor and quality formation mechanisms based on the microbial metabolism of Huangjiu. Here, metagenome techniques, chemometrics analysis, and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) metabolomics combined with microbial metabolic network were employed to investigate the distinctions and relationship between the microbial profiles and the quality characteristics, flavor metabolites, functional metabolic patterns of Huangjiu across three regions. Significant variations (P < 0.05) were observed in metabolic rate of physicochemical parameters and biogenic amine concentration among three regions. 8 aroma compounds (phenethyl acetate, phenylethyl alcohol, isobutyl alcohol, ethyl octanoate, ethyl acetate, ethyl hexanoate, isoamyl alcohol, and diethyl succinate) out of 448 volatile compounds were identified as the regional chemical markers. 25 dominant microbial genera were observed through metagenomic analysis, and 13 species were confirmed as microbial markers in three regions. A metabolic network analysis revealed that Saccharomycetales (Saccharomyces), Lactobacillales (Lactobacillus, Weissella, and Leuconostoc), and Eurotiales (Aspergillus) were the predominant populations responsible for substrate, flavor (mainly esters and phenylethyl alcohol) metabolism, Lactobacillales and Enterobacterales were closely linked with biogenic amine. These findings provide scientific evidence for regional microbial contributions to geographical characteristics of Huangjiu, and perspectives for optimizing microbial function to promote Huangjiu quality.

Transcriptomics to evaluate the influence mechanisms of ethanol on the ester production of Wickerhamomyces anomalus with the induction of lactic acid.

Wickerhamomyces anomalus is one of the most important ester-producing strains in Chinese baijiu brewing. Ethanol and lactic acid are the main metabolites produced during baijiu brewing, but their synergistic influence on the growth and ester production of W. anomalus is unclear. Therefore, in this paper, based on the contents of ethanol and lactic acid during Te-flavor baijiu brewing, the effects of different ethanol concentrations (3, 6, and 9% (v/v)) combined with 1% lactic acid on the growth and ester production of W. anomalus NCUF307.1 were studied and their influence mechanisms were analyzed by transcriptomics. The results showed that the growth of W. anomalus NCUF307.1 under the induction of lactic acid was inhibited by ethanol. Although self-repair mechanism of W. anomalus NCUF307.1 induced by lactic acid was initiated at all concentrations of ethanol, resulting in significant up-regulation of genes related to the Genetic Information Processing pathway, such as cell cycle-yeast, meiosis-yeast, DNA replication and other pathways. However, the accumulation of reactive oxygen species and the inhibition of pathways associated with carbohydrate and amino acid metabolism may be the main reason for the inhibition of growth in W. anomalus NCUF307.1. In addition, 3% and 6% ethanol combined with 1% lactic acid could promote the ester production of W. anomalus NCUF307.1, which may be related to the up-regulation of EAT1, ADH5 and TGL5 genes, while the inhibition in 9% ethanol may be related to down-regulation of ATF2, EAT1, ADH2, ADH5, and TGL3 genes.

Selection of adjunct cultures for the ripening of plant cheese analogues.

Fermentation contributes to the taste and odor of plant cheeses. The selection of functional cultures for the fermentation of plant cheeses, however, is in its infancy. This study aimed to select lactic acid bacteria for ripening of soy and lupin cheese analogues. Bacillus velezensis and B. amyloliquefaciens were used for germination of seeds to produce proteolytic enzymes; Lactococcus lactis and Lactiplantibacillus plantarum served as primary acidifying cultures. Levilactobacillus hammesii, Furfurilactobacillus milii, or Lentilactobacillus buchneri were assessed as adjunct cultures for the ripening of plant cheese. Growth of bacilli was inhibited at low pH. Both Lc. lactis and Lp. plantarum were inactived during plant cheese ripening. Cell counts of Lv. hammesii remained stable over 45 d of ripening while Ff. milii and Lt. buchneri grew slowly. Sequencing of full length 16S rRNA genes confirmed that the inocula the plant cheeses accounted for more than 98% of the bacterial communities. HPLC analysis revealed that Lt. buchneri metabolized lactate to acetate and 1,2-propanediol during ripening. Bacilli enhanced proteolysis as measured by quantification of free amino nitrogen, and the release of glutamate. LC-MS/MS analysis quantified kokumi-active dipeptides. The concentrations of γ-Glu-Leu, γ-Glu-Ile, and γ-Glu-Ala, γ-Glu-Cys in unripened cheeses were increased by seed germination but γ-Glu-Phe was degraded. Lt. buchneri but not Lv. hammesii or Ff. milii accumulated γ-Glu-Val, γ-Glu-Ile or γ-Glu-Leu during ripening, indicating strain-specific differences. In conclusion, a consortium of bacilli, acidification cultures and adjunct cultures accumulates taste- and kokumi-active compounds during ripening of plant cheeses.