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Summary: Paocai, as one of the most widely consumed traditional fermented foods in China, is dominated by lactic acid bacteria (LAB), which exert a significant influence on the dynamics of metabolites, microecological changes, and sensory quality. In this study, five different paocai groups were designed for fermentation using Lactiplantibacillus plantarum HYY‐DB9 (LP), Levilactobacillus brevis GIM 1.773 (LB), a mixture of two LABs (LP + LB), pasteurisation (PST), and natural fermentation (NF). Nitrite content, pH, titratable acidity, viable cell counts (LAB and yeasts), metabolites (organic acids and volatile substances), and sensory evaluation were determined for each group. The results demonstrated that the mixed fermentation with two LABs (LP + LB) significantly reduced nitrite content. Organic acids produced by LAB played a crucial role in the degradation process, particularly lactic acid which exhibited the most pronounced effect on nitrite degradation. Furthermore, artificial inoculation of LAB fermentation resulted in improved taste and flavour of paocai along with increased production of alcohols, esters, and acids compared to traditional natural fermentation. These findings have important implications for enhancing paocai quality control and managing nitrite content while also providing an excellent fermentation agent for fermented paocai. [ABSTRACT FROM AUTHOR]

Summary: In this study, six groups of carrots were designed and fermented using Weissella paramensenteroides MbWp142 (WP), Levilactobacillus brevis GDMCC 1.773 (LS), Leuconostoc mesenteroides GDMCC 1.774 (SE), mixed fermentation of three lactic acid bacteria (WP + LS + SE), pasteurisation group (BG) and natural fermentation group (CK). GC–MS results indicated that inoculation of WP + LS + SE increased the types and contents of flavour substances such as alcohols, esters and hydrocarbons. Compared with other experimental groups, the peak nitrite value in the LS group was lower due to the production of organic acids by lactic acid bacteria. Sensory evaluation revealed that the quality and flavour of carrot fermented by LS were superior to those fermented by SE, WP and WP + LS + SE. Therefore, Levilactobacillus brevis used as a starter for fermenting carrot can enhance product quality and reduce nitrite accumulation during fermentation. [ABSTRACT FROM AUTHOR]

Summary: Fermented vegetables are nutritionally beneficial and promote good health. China possesses abundant raw vegetable materials and has a longstanding history of fermented vegetable production. However, the traditional process of vegetable fermentation heavily relies on individual producers' experience and knowledge, resulting in inconsistent flavours, variable quality, and the potential generation of harmful substances. The utilisation of lactic acid fermentation starters can effectively inhibit pathogenic bacteria during the fermentation process, enhance product flavour, reduce nitrite production, improve functional and nutritional value, as well as extend shelf‐life. This article comprehensively reviews factors influencing vegetable fermentation; diverse functions performed by lactic acid bacteria throughout the fermentation process and assesses the current industrialisation status of vegetable fermentation in China. It serves as a valuable reference for promoting high‐quality development within the fermented vegetable industry. [ABSTRACT FROM AUTHOR]

Summary: Carbon dioxide (CO2) has the potential to extend the storage time of raw milk, but its industrial application in this regard has not been thoroughly explored. This study aimed to investigate the microflora of CO2‐treated and untreated raw milk from South China using Illumina sequencing. The sequencing results confirmed the presence of Delftia, Pseudomonas and Serratia as the main spoilage species in raw cow milk from South China. However, CO2 treatment was found to selectively inhibit the growth of these spoilage bacteria. Principal coordinate analysis revealed differences in the microbiota structures of samples collected from the Fuyi and Guanyuan sites. Additionally, a total of 119 and 120 bacterial species were identified in the Fuyi and Guanyuan samples, respectively. The spoilage of raw milk from the Fuyi and Guanyuan was delayed by 7 and 19 days, respectively, with the application of CO2 treatment. Conversely, the samples without CO2 treatment were found to be contaminated with Pseudomonas fluorescens and Serratia. Moreover, the CO2‐treated samples from the Fuyi and Guanyuan ranches exhibited a different composition of spoilage bacteria, with a significant increase in the number of lactic acid bacteria (LAB) compared to the control samples. This study suggests that LAB have a remarkable tolerance to CO2, which is consistent with their selection in fruit, vegetable and meat products stored in CO2‐enriched modified atmosphere packaging. The findings of this study provide a foundation for further exploration of the potential application of CO2 treatment in raw milk processing. [ABSTRACT FROM AUTHOR]

The lactic acid bacteria (LAB) are a group of Gram-positive, non-respiring, non-spore-forming bacteria, cocci or rods, which produce lactic acid as the solely or main end product of carbohydrates fermentation. Some strains of LAB are probiotics that play important role in food processing and safety, as well as in maintaining human health as an integral part of the microbiota, that could be widely found in fermented foods, such as yogurt, cheese, kimchi, and wine. Streptococcus thermophilus, a species of LAB, exhibits probiotic effects, including alleviation of lactose intolerance, chronic gastritis, diarrhea, and bacteriostatic effects on pathogens. Recently, S. thermophilus in fermented products has attracted increasing research interest. However, the sources of new isolates of S. thermophilus are limited, so it is necessary to screen a large number of diverse habitats and functionally enriched selection to discover new and useful strains. This review summarizes the results related to insulation and identification, safety assessments and metabolic properties of S. thermophilus. Functional properties, its application in the production of fermented products, the development of new perspectives, as well as shortcomings are discussed in detail, in order to facilitate future research and application of S. thermophilus. [ABSTRACT FROM AUTHOR]

The nitrite that normally exists in fermented foods is a threat to public health. Nitrite degradation by lactic acid bacteria (LAB) has the advantages of safety and low cost. This study investigated the effect of Lactobacillus plantarum DMDL 9010 (LP9010) on growth phenotype under nitrite stress from the perspective of whole genome sequencing. The results showed that LP9010 has certain tolerance to nitrite. However, high nitrite concentration (5–12.5 mmol/L) inhibited the growth and acid production. Nitrite could not only affect the morphology of LP9010 cells with longer phenotype, shrink and dent on the surface (even crack), but also decreased cell surface hydrophobicity. Correspondingly, 19 genes encoding stress proteins have been found in the genome. In addition, genes related to osmotic regulation proteins and peptidoglycans synthesis were found in the genome of LP9010, which may affect the cell wall structure under nitrite stress. Low pH lactic acid could degrade nitrite, whereas nitrite was hardly degraded when pH > 4. In addition, we found the putative nitrite reductase gene in LP9010, the nitrite ion bound to the Cd1 NiR (pgl) active site by forming two hydrogen bonds with the residues PRO87 and PRO88. This study could provide theoretical reference to reduce nitrite in food products. • Complete genome of L. plantarum DMDL 9010 (LP9010) was firstly sequenced. • This is the first report of nitrite degradation activity of LP9010 by genome sequence and corresponding phenotypes. • LP9010 has the potential to be used as probiotics to degrade nitrites. [ABSTRACT FROM AUTHOR]

Paocai is one of the most popular traditional fermented products in China. Different lactic acid bacteria (LAB) have an important influence on the microbial changes, the dynamic changes of metabolites, and the sensory qualities of paocai. In this study, five different paocai groups were designed which were fermented by Lactobacillus plantarum DMDL 9010 (LP), Lactobacillus brevis GIM 1.773 (LB), Leuconostoc mesenteroides GIM 1.774 (LM), mixed three kinds of LAB (LP + LB + LM), pasteurization (PST) and natural fermentation (NF) without LAB. The nitrite, nitrate, pH, titratable acidity, viable count (LAB and yeast) and metabolites (organic acids, sugars and volatile substances) of these paocai groups were measured. Compared with each single bacterial fermentation (LP, LB and LM), NF and PST, the mixed three kinds of LAB (LP + LB + LM) had a lower nitrite peak, which could be attributed to the significant accumulation of organic acids, and positively affected sensory quality of paocai. Flavor substances produced in paocai samples confirmed as alcohols, ketones and olefins. Sensory evaluation showed that multi-bacteria mixed fermentation of paocai had a better flavor than that of NF, PST and single bacterial fermentation. Therefore, the use of multiple LAB as starter cultures contributes to enhance paocai qualities and control the levels of nitrite. • Effect of different lactic acid bacteria (LAB) on nitrite degradation and quality in paocai. • The three kinds of LAB mixed fermentation could significantly reduce the content of nitrite. • Natural fermentation and multi-bacterial mixed fermentation of paocai had a better flavor than single-bacterial fermentation. [ABSTRACT FROM AUTHOR]

Yogurt-flavored bases are widely used in food industry for enhancing flavors. In this study, yogurt-flavored bases by mixed lactic acid bacteria with or without lipase were investigated, which included Streptococcus lactis ACCC 11093 (SL) and Lactobacillus casei subsp. rhamnosus 6013 (LCR), SL and Lactobacillus acidophilus 1.1878 (LAP), and SL and Lactobacillus plantarum DMDL 9010 (LP), respectively. Compared with the combination of SL and LCR and the combination of SL and LAP, the combination of SL and LP had higher production of total amino acids, volatile acids and esters, suggesting that the combination of SL and LP was more efficient to produce yogurt-flavored bases. In addition, lipase significantly increased the production of amino acids associated with sweet and bitter flavors, and resulted in rougher milk globule surface and tighter network structure compared with fermentations without the addition of lipase. Furthermore, a total of 54 volatile compounds were detected in yogurt-flavored bases. The production of volatile compounds in fermentations with and without the addition of lipase, was mainly affected by acids and esters, respectively. Therefore, the lipase is a favorable supplement for producing yogurt-flavored bases. • Fermented yogurt-flavored bases with lactic acid bacteria can produce more kinds of volatile compounds. • Addition of lipase affected amino acids, network structure and fatty acids of yogurt flavor bases. • Addition of lipase increased the abundance of key volatile compounds. • The lipase treatment is a good option to improve flavor of food matrix. [ABSTRACT FROM AUTHOR]

Bacillus coagulans was classified as sporogenic lactic acid bacteria and served as a vital potential probiotic. We reported the whole genome sequence of Bacillus coagulans 13002 which was assessed for the safety and probiotic properties based on complete genome in cooperation with phenotype analysis. The complete genome sequence demonstrated a single scaffold of 3,609781 bp with an average guanine and cytosine (GC) content of 46.86% and 3972 protein coding genes. The taxonomic status of the strain was established based on 1352 single copy orthologs genes. Clusters of Orthologous Groups (COG) annotation classified the predicted proteins with the function of cellular, metabolism and information from assembled genome. Risk related sequences corresponding antibiotic resistance genes, virulence factor genes and toxin encoding genes were identified and confirmed to be safe associated with acute oral toxicology test, hemolytic assay and antibiotic resistance test. Two gene clusters of circular antimicrobial peptides were detected by genome mining tools. Adhesion related genes and stress-responsive genes associated with tolerance tests such as the acid, bile salts and antioxidant activity in vitro, exhibited the excellent probiotic properties indicating the potential candidate as a probiotic. • Complete genome of B. coagulans 13002 was firstly sequenced. • Systematic analysis of its probiotics and safety based on phenotype and genotype. • Analyzed the bacteriocin-related genes in the genome. • Superoxide dismutase gene was found, which was generally absent in some probiotics. [ABSTRACT FROM AUTHOR]