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Ergothioneine (EGT) is a high-value natural sulfur-containing amino acid and has been shown to possess extremely potent antioxidant and cytoprotective activities. At present, EGT has been widely used in food, functional food, cosmetics, medicine, and other industries, but its low yield is still an urgent problem to overcome. This review briefly introduced the biological activities and functions of EGT, and expounded its specific applications in food, functional food, cosmetic, and medical industries, introduced and compared the main production methods of EGT and respective biosynthetic pathways in different microorganisms. Furthermore, the use of genetic and metabolic engineering methods to improve EGT production was discussed. In addition, the incorporation of some food-derived EGT-producing strains into fermentation process will allow the EGT to act as a new functional factor in the fermented foods.

Background: Paocai is a traditional Chinese fermented vegetable food. As the most important ingredient, salt has crucial effects on the bacterial community and volatile compounds of paocai. To demonstrate the effects of salt on the fermentation of paocai, the bacterial composition and volatile compounds were investigated using high-throughput sequencing and gas chromatography-mass spectrometry (GC-MS)., Results: The salt had no significant effects on the bacterial community at the phylum level. Proteobacteria and Bacteroidetes gradually decreased during the fermentation, and Firmicutes gradually increased as the dominant bacteria in the late stage of fermentation. At the genus level, Lactobacillus and Lactococcus gradually increased in relative abundance during the fermentation and became the dominant bacteria in paocai. High salt levels can contribute to the growth of Lactobacillus, which became the dominant genus in paocai. The salt concentration affected the profiles of volatile compounds in paocai after fermentation. A total of 42 volatile components were detected by GC-MS, among which phenols, aldehydes, and nitriles were the main ones. A high salt concentration will increase the volatile compound content, mainly aldehydes and alcohols, and improve the flavor of paocai. At the same time, the electronic tongue analysis also showed that a high salt concentration made a major contribution to the flavor of paocai., Conclusions: These data are helpful to elucidate the effects of salt on the quality of paocai and contribute to improving the quality and reducing the use of salt. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

Flavourzyme is known to promote protein decomposition, resulting in more peptides and amino acids which can improve the quality of fermented foods. In this study, the effects of flavourzyme addition on the fermentation of Suanzhayu fish were investigated. The results showed that the addition of 50 U/g flavourzyme reduced the water activity (a w ) of products and promoted the release of trichloroacetic acid (TCA)-soluble peptides and free amino acids (FAAs). Thus, the stability of the product was improved and its nutritional value was increased. In addition, with the addition of flavourzyme, Lactobacillus and Saccharomyces more quickly became the dominant genera in the fermentation. Furthermore, the formation of alcohols, aldehydes, and esters was promoted in flavourzyme addition group. Redundant analysis (RDA) indicated that Lactobacillus and Lactococcus play important roles in the formation of flavors, especially for the characteristic flavors of Suanzhayu. Flavourzyme addition may be a novel method to greatly improve the properties of Suanzhayu and shorten the fermentation time., Competing Interests: Declaration of competing interest The authors have no conflict of interest to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Suancai is a popular fermented product of Brassica vegetable in China. As important additive, salt concentration has crucial effects on the quality of suancai. To investigate the effects of salt concentration on suancai fermentation, the microbial diversity and volatile compounds (VCs) during fermentation were investigated by using Illumina HiSeq sequencing and GC-MS. Firmicutes, Proteobacteria and Ascomycota were detected as the main phylum during the fermentation with different salt concentrations. Lactobacillus, Lactococcus, Klebsiella, Weissella, Pediococcus, Candida, Cladosporium, Gibberella, Aspergillus, etc., were detected were observed during the fermentation with different concentrations. After fermentation, Lactobacillus predominated the fermentation of suancai and was not affected by salt concentration. Pediococcus, Leuconostoc, Weissella, Sporobolomyces, Azospirillum, Klebsiella, Acinetobacter and Cladosporium were significant affected by salt concentration. Salt addition could affect the VCs profiles and reduce the isothiocyanates after fermentation. Seventy-nine VCs were detected and strongly correlated with the dominant genus Lactobacillus during suancai fermentation. The inoculated fermentation of Lactobacillus could improve the VCs during fermentation. In conclusion, 6% salt addition could acquire a higher Lactobacillus abundance and a better taste quality. These results may facilitate the understanding of the effect of salt concentration on the fermentation ecology to improve suancai characteristics., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study was designed to explore the temperature effects on bacterial communities and metabolites, as well as their relationships during the fermentation of sour meat, a traditional fermented meat product in the ethnic minority regions of China. Results showed that reduction of pH and increase of lactic acid and free amino acid contents occurred (p < 0.05) as the fermentation temperature and time increased, and the tendency was more apparent at higher temperature. During the fermentation, Lactobacillus gradually replaced other genera, and higher the temperature, more rapid was the process. Both the number and amount of volatile organic compounds increased at higher temperatures. Hexanal, benzaldehyde, nonanal, (E,E)-2,4-decadienal, 1-octen-3-ol and octanal were identified as the key volatile organic compounds produced by Lactobacillus in sour meat as main contributors to odor as confirmed by variable importance in the projection analysis. Redundancy analysis and Pearson correlation showed positive correlation between Lactobacillus and desired product characteristics, such as higher content of lactic acid, free amino acids, volatile organic compounds, and lower pH and water activity values, which may represent a better quality and longer shelf life after fermentation at higher temperature. Therefore fermentation at 20 °C and 25 °C are proposed as optimum temperatures for sour meat production., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Morganella morganii, a spoilage bacterium in fermented foods, produces harmful biogenic amines (BAs). Although Lactiplantibacillus plantarum is widely used to inhibit spoilage bacteria, the inhibition pattern and inhibition mechanism of M. morganii by Lpb. plantarum are not well studied. In this study, we analysed the effects of the addition of Lpb. plantarum cell-free supernatant (CFS) on the growth and BA accumulation of M. morganii and revealed the mechanisms of changes in different BAs by using RNA sequencing transcriptome analysis. The results showed that Lpb. plantarum CFS could significantly inhibit M. morganii BAs in a weak acid environment (pH 6), and the main changes were related to metabolism. Carbohydrate and energy metabolism were significantly down-regulated, indicating that Lpb. plantarum CFS inhibited the growth activity and decreased the BA content of M. morganii. In addition, the change in histamine content is also related to the metabolism of its precursor amino acids, the change in putrescine content may also be related to the decrease in precursor amino acid synthesis and amino acid transporter, and the decrease in cadaverine content may also be related to the decrease in the cadaverine transporter. The results of this study help to inhibit the accumulation of harmful metabolites in fermented foods. [ABSTRACT FROM AUTHOR]

In this study, three Lactiplantibacillus plantarum, namely 3-14-LJ, M22, and MB1, with high acetate esterase activity, acid, salt, and high-temperature tolerance were selected from 708 strains isolated from fermented food. Then, L. plantarum strains MB1, M22, and 3-14-LJ were inoculated at 107 CFU/mL in the model and 107 CFU/g in actual Suanzhayu systems, and the effects during fermentation on the physicochemical properties, amino acid, and volatile substance were investigated. The results showed that the inoculated group had a faster pH decrease, lower protein content, higher TCA-soluble peptides, and total amino acid contents than the control group in both systems (p < 0.05). Inoculation was also found to increase the production of volatile compounds, particularly esters, improve the sour taste, and decrease the bitterness of the product (p < 0.05). L. plantarum M22 was more effective than the other two strains in stimulating the production of isoamyl acetate, ethyl hexanoate, and ethyl octanoate. However, differences were discovered between the strains as well as between the model and the actual systems. Overall, the isolated strains, particularly L. plantarum M22, have good fermentation characteristics and have the potential to become excellent Suanzhayu fermenters in the future. [ABSTRACT FROM AUTHOR]

Ethyl carbamate (EC), classified as a Group 2A carcinogen, is most abundant in the fermented foods, such as Cachaca, Shaoxing wine, and Chinese liquor (baijiu). Although biodegradation can reduce its concentration, a high ethanol concentration and acidic environment often limit its degradation. In the present study, a novel ethyl carbamate hydrolase (ECH) with high specificity to EC was isolated from Acinetobacter calcoaceticus, and its enzymatic properties and EC degradability were investigated. ECH was immobilized to resist extreme environmental conditions, and the flavor substance changes were explored by gas chromatography-mass spectrometry (GC/MS). The specific enzymatic activity of ECH was 68.31 U/mg. Notably, ECH exhibited excellent thermal stability and tolerance to sodium chloride and high ethanol concentration (remaining at 40% activity in 60% (v/v) ethanol, 1 h). The treatment of immobilized ECH for 12 h decreased the EC concentration in liquor by 71.6 μg/L. Furthermore, the immobilized ECH exerted less effect on its activity and on the flavor substances, which could be easily filtrated during industrial production. [ABSTRACT FROM AUTHOR]

The increasing demand for healthy food has led to a broad interest in developing new food products containing probiotics in recent years. In this study, the potential of probiotics and prebiotics was assessed to develop novel gummies. The results showed probiotic properties in twenty-five Lactobacillus plantarum (L. plantarum) strains derived from fermented foods, confirming them to be safe for consumers, which can tolerate the simulated gastrointestinal fluids (SGIF) to a certain extent. Additionally, the DPPH free radical ranging between 13.67 ± 0.35 to 15.98 ± 0.28 mg AAE/L was expressed as ascorbic acid equivalent (AAE). Afterward, the results showed that six mushroom polysaccharides had a proliferative effect on most potential probiotics. Besides, they could further protect the survival of L. plantarum YC-5 in the SGIF. With the protection of prebiotics, the number of viable cells in SGIF exceeded 7 log CFU/mL. The genomic analysis demonstrated that 106 genes were involved in saccharide metabolism in L. plantarum YC-5. Finally, probiotics and prebiotics were used as raw materials to prepare the gummies. The results indicated that the gummies protected the probiotic L. plantarum YC-5 with little loss of activity in the SGIF. Therefore, preparing probiotics and prebiotics as gummies could be a promising probiotic food application. • Four strains of Lactobacillus plantarum screened for probiotic potential. • Mushroom polysaccharides proliferated and protected against L. plantarum YC-5. • Preparation probiotics and prebiotics as gummies. [ABSTRACT FROM AUTHOR]

The bacterial diversity and volatile flavor compounds (VFCs) during suancai fermentation in different temperatures were investigated by Illumina Hiseq sequencing and GC-MS. Firmicutes and Proteobacteria were observed to be the dominant phyla during the fermentation. Lactobacillus , Serratia , Leuconostoc , Pseudomonas , Pseudomonas , Pediococcus , etc., were observed as the main genus. Serratia and Pseudomonas predominated the early stage of suancai fermentation, while Lactobacillus predominated the later stage. Leuconostoc predominated the fermentation at 10 °C and 15 °C, while Weissella and Lactococcus predominated at 20 °C and 25 °C. A total of 86 VFCs were detected in all suancai samples. With the increase of the fermentation temperature, the kinds of VFCs were also increased. Lactobacillus , Pediococcus , Lactococcus , Brochothrix , Psychrobacter , Pseudoalteromonas , Acinetobacter and Enterobacter were the important bacteria related to VFCs during the fermentation. The bacteria were highly correlated with the VFCs in suancai fermentation. As the most dominant genus, Lactobacillus was significantly positive correlated with 13 VFCs. The correlation between the bacteria and VFCs in suancai could be used to search for microbial markers. In conclusion, 20 °C could accelerate the maturation and improve the sensory quality of suancai. This study could provide useful guidelines for screening of strains that contribute to the flavor formation in suancai fermentation. • Firmicutes and Proteobacteria were observed as dominant phylum in suancai. • Lactobacillus predominated the later stage of the suancai fermentation. • The biomarkers in suancai fermented under different temperature were different. • Eight important genera were significant correlated with the VFCs in suancai. • Lactobacillus was significant positive correlated with 13 VFCs in suancai. [ABSTRACT FROM AUTHOR]