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In this study, three

Saccharomyces cerevisiae is commonly used as a starter culture for alcoholic beverages but is less applied in meat products. In this study, the effects of S. cerevisiae LXPSC1 on sour meat during fermentation were investigated. It was found that samples inoculated with S. cerevisiae LXPSC1 (Sc group) had better sensory characteristics and higher levels of pH, ethanol, free amino acids (FAAs), volatile organic compounds (VOCs). The bacterial communities of both groups were dominated by Lactobacillus sakei, Weissella hellenica, and Lactobacillus plantarum, which might play a role in reducing pH and a

This work investigated the effect of lipase addition on a Chinese traditional fermented fish product, Suanzhayu. The accumulation of lactic acid and the decrease of pH during the fermentation were mainly caused by the metabolism of Lactobacillus. The addition of lipase had little effect on pH and the bacterial community structure but promoted the growth of Proteus. The addition of lipase promotes the formation of volatile compounds, especially aldehydes and esters. The formation of volatile compounds is mainly divided into three stages, and lipase had accelerated the fermentation process. Lactobacillus, Enterococcus and Proteus played an important role not only in inhibition of the growth of Escherichia-Shigella, but also in the formation of flavor. This study provides a rapid fermentation method for the Suanzhayu process.

Biogenic amines (BA) are often present at high concentrations in fermented meat and cause foodborne illness. The aim of this work was to screen amine-degrading starters for Roucha (a fermented meat) to improve product safety and quality. Firstly, Weissella viridescens F2 and Lactiplantibacillus plantarum His6 with multi-copper oxidase activity and high degradation rates towards histamine and tyramine were selected as single or mixed starters. Additionally, the effect of starters on bacterial community succession, acid production, BA accumulation, free amino acid profiles, and volatile compound profiles were evaluated during the fermentation of Roucha. Results indicated that all starters could effectively reduce the accumulation of BA in Roucha. At the end of fermentation, Lpb. plantarum His6 as a single starter reduced the histamine level (38.15 %), while mixed starters (Lpb. plantarum His6 + W. viridescens F2) possessed a high tyramine-reduction rate (54.95 %) and total BA-reduction rate (46.64 %). Bacterial succession analysis revealed that starters could help establish the dominance of lactobacilli or Weissella quickly, which contributed to the direct degradation of BA and inhibited the growth of amine-producing bacteria. Furthermore, Lpb. plantarum His6 could promote the accumulation of essential amino acids (leucine, phenylalanine, threonine, isoleucine), sweet and umami amino acids (glycine, threonine, glutamate), and volatile compounds of good odor, indicating that this strain greatly contributed to the development of good taste and aroma characteristics in Roucha. Overall, this work shows that the application of amine-degrading starters is an effective strategy to reduce the BA accumulation and improve the quality of Roucha. Thus, these findings can provide foundations for the industrial production of Roucha.

Yucha is a home-made, fermented fish product in South China. The quality of yucha can vary depending on environmental factors. In order to determine the effects of temperature on bacterial ...

Nine transformants of Rhodosporidium toruloides with significant changes in the carotenoid profile were obtained by Agrobacterium tumefaciens-mediated transformation, including a white, three red, and four yellow mutants. A red mutant A1-15-BRQ that showed a high torularhodin production was selected for culture condition optimization. Results indicated that the torularhodin yield was boosted with glucose as the carbon source, at a carbon/nitrogen ratio of 22, a loading volume of 75 mL, and 28 °C. The torularhodin yield of 21.3 mg/L consisting of 94.4% total carotenoids was obtained by Box-Behnken design experiments. The torularhodin yield was 17.0-fold higher than that of the wild type, with time shortened from 9 to 3 days. This study reports an effective strategy for improving torularhodin production and provides a candidate R. toruloides strain for highly selective production of torularhodin.

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.

The quality characteristics of Suancai fermented with Lactobacillus plantarum CGMCC No.20193 (Lb. plantarum) and Pediococcus pentosaceus CGMCC No. 20192 (P. pentosaceus) were investigated. Their inoculation affected the bacterial communities revealed by Pacbio Sequel platform. After fermentation, the dominant phylum and genus in inoculation and spontaneous fermented Suancai were Firmicutes and Lactobacillus. Compared with single inoculation, the co-inoculation of Lb. plantarum and P. pentosaceus had a higher bacterial diversity. The Suancai co-inoculated with Lb. plantarum and P. pentosaceus had a more similar VCs profile with spontaneous fermented Suancai. The inoculation of Lb. plantarum and P. pentosaceus increased the content of organic acids, such as lactate, acetate, citrate, succinate, malate and tartrate. The most amino acids content in Suancai fermented with Lb. plantarum and P. pentosaceus were higher than that in spontaneous fermented Suancai. Compared single inoculation, the Suancai co-inoculated with Lb. plantarum and P. pentosaceus had a higher similarity of organoleptic tastes with spontaneous fermented Suancai. These results may facilitate the understanding of the starters' effects on the Suancai fermentation and the selection of applicable starters to manipulate the flavor.

Paocai is a traditional Chinese fermented food and typically produced via spontaneous fermentation. We have investigated the microbial community utilized for the fermentation of industrialized Qingcai paocai using the combination of Illumina MiSeq sequencing, PCR-mediated denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative PCR (qPCR) assay. Three main phyla, namely Firmicutes, Proteobacteria and Bacteroidetes, were identified by both MiSeq sequencing and PCR-DGGE. The dominant genera observed in the fermentation were Lactobacillus, Pseudomonas, Vibrio and Halomonas. Most genera affiliated with Proteobacteria or Bacteroidetes were detected more often during the earlier part of the fermentation, while Lactobacillus (affiliated with Firmicutes) was dominant during the later fermentation stages. Fungal community analysis revealed that Debaryomyces, Pichia and Kazachstania were the main fungal genera present in industrialized Qingcai paocai, with Debaryomyces being the most dominant during the fermentation process. The quantities of dominant genera Lactobacillus and Debaryomyces were monitored using qPCR and shown to be 109–1012 and 106–1010 copies/mL, respectively. During the later fermentation process of industrialized Qingcai paocai, Lactobacillus and Debaryomyces were present at 1011 and 108 copies/mL, respectively. These results facilitate further understanding of the unique microbial ecosystem during the fermentation of industrialized Qingcai paocai and guide future improvement of the fermentation process.

Little is known about the relationship between the chemical and microbial properties of Chouguiyu, a traditional Chinese fermented fish with unique aroma and plentiful taste. Therefore, we explored this relationship by determining the bacterial and fungal distribution of 14 brands of Chouguiyu. The distribution of microorganism and their effect on product quality, such as volatile flavor compounds (VFCs), free amino acids (FAA), physicochemical features and organoleptic properties were evaluated. Five VFCs (2-ethyl-1-hexanol, eucalyptol, 1-octen-3-ol, nonanal and indole) and three FAAs (Glu, Vla and Ala) were considered as core components. LAB (Vagococcus and Lactococcus) were found to contribute greatly to critical aroma formation and inhibition of TVB-N, leading to a moderate fermentation and good quality. While excessive increases in TVB-N, VFCs and FAA contents were found to be related with Psychrilyobacter and Fusobacterium, leading to poor organoleptic properties. The addition of Sufu to these products may be associated with the accelerating the fermentation process. Moderate fermentation with LAB is beneficial to typical aroma and good organoleptic properties, while excessive fermentation related with Psychrilyobacter and Fusobacterium may lead to overpowering flavors and lowered organoleptic properties.

This paper aimed to investigate the dose-effects of l -Lysine (Lys, 0.2% to 0.8%) on the water holding capacity (WHC), textural properties, water mobility and distribution, microstructures and sensory acceptance of reconstructed ham with 50% reduction of added salt. Results showed that reducing salt from 2.50% to 1.25% caused significant increase in cooking loss and centrifuge loss, and decrease in hardness, springiness and chewiness. 0.8% Lys significantly improved the WHC and textural properties of salt-reduced hams, whereas 0.2% Lys further impaired these attributes. Moreover, 0.8% Lys improved the sensory scores for mouthfeel, appearance, taste and global acceptance. The NMR analysis reveals that water distribution and mobility were affected by salt reduction and Lys addition, and hams with 0.8% Lys contained more entrapped water with decreased mobility. Furthermore, a fine network with more bridge-linkage among myofibrils was formed in hams with 0.8% Lys. Therefore, addition of 0.8% Lys showed great potential in developing salt-reduced reconstructed ham with premium technological and sensory qualities.

Rhodosporidium toruloides has been reported as a potential biotechnological microorganism to produce carotenoids. The most commonly used molecular and genetic manipulation methods based on Agrobacterium-mediated transformation (ATMT). However, this method was of relatively lower transformation efficiency. In this study, we optimized the ATMT method for R. toruloides on account of the promoter on T-DNA, the ratio of A. tumefaciens to R. toruloides NP11, acetosyringone concentration, cocultivation temperature and time, and a transformation efficiency of 2,369 cells per 105 recipient cells was obtained and was 24 times as that of the previous report. With this optimized method, four redder mutants and four yellower mutants were selected out with torularhodin and β-carotene production preference, respectively. The highest torularhodin production was 1,638.15 µg/g dry cell weight in A1-13. The yellower mutants were found to divert the metabolic flux from torularhodin and torulene to γ-carotene and β-carotene, and the proportion of γ-carotene and β-carotene were all over 92%. TAIL-PCR was carried out to found T-DNA insertion in these mutants, and insertion hotspot was found. RT-qPCR results showed that CTA1 genes in these mutants were closely related to the synthesis of total carotenoids, especially torularhodin, and was a potenial metabolic engineering site in the future.

The bacterial community in the pit mud of a Luzhou-flavour liquor distillery in different regions was analysed by combined polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative PCR (qPCR) in order to distinguish a matured and a degenerated pit mud, judged according to sensory and physicochemical characteristics. The phyla Firmicutes, Cloacimonetes, Actinobacteria, Proteobacteria, Synergistetes and Unclassified Bacteria were detected. Firmicutes predominated in the pit mud. The diversity and homogeneity of the bacterial community in the matured pit mud were superior to those in the degenerated pit mud in the same distillery. There were significant differences in the bacterial community structure between the matured and degenerated pit mud. Moreover, the bacterial community in the degenerated pit mud samples was similar, which indicated that the bacterial community in the degenerated pit mud did not change within the two different regions. However, the bacterial community in matured pit mud samples was different, demonstrating that there were visible differences in the bacterial community between the samples of matured pit mud collected from the Luzhou-flavour liquor distilleries in the two different regions. Notably, the quantity of Actinobacteria in the matured and the degenerated pit mud was found to be different by quantitative analysis. Potentially, the Actinobacteria could serve as an indicator bacteria to distinguish between matured and degenerated pit muds. Copyright © 2015 The Institute of Brewing & Distilling

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 (aw) 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.

Suancai, a popular traditional fermented cabbage in northeast China, is commonly prepared by the spontaneous fermentation process at a certain salt concentration. The salt can affect the metabolites by affecting the microorganisms during Suancai fermentation. The bacterial community and volatile flavor compounds in commercial Suancai from different regions of Northeastern China at different salt concentrations were investigated using next-generation sequencing and GC-MS. Firmicutes and Cyanobacteria were the dominant phyla in the commercial Suancai, and Lactobacillus, Pediococcus, and Leuconostoc were the dominant genera. Among them, Lactobacillus and Pediococcus were considered as the biomarkers of the low and high salt Suncai, respectively. Eighty-five volatile flavor compounds were detected, and HS exhibited higher contents of volatile flavor compounds than LS. Based on the results of correlation analysis, Pediococcus were highly correlated with the alcohols and nitriles in Suancai. The contents of alcohols and nitriles significantly increased in the Suancai, fermented by Pediococcus pentosaceus. The co-inoculated fermentation of Lactobacillus plantarum and P. pentosaceus could increase the concentrations of alcohols, esters, aldehydes, hydrocarbons, and nitriles in Suancai. This study provides a perspective for understanding the ecology of Suancai fermentation and facilitating the fermentation with multispecies inoculation fermentation at an appropriate salt concentration.

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.

Chouguiyu (stinky Mandarin fish), a traditional spontaneously fermented fish in China, is famous for its unique aroma and pleasant taste. However, the relationships between the succession of microorganisms during the fermentation and the formation of Chouguiyu's unique aroma and taste remain to be characterized. In this study, 16S rRNA gene amplicon sequencing was done to investigate the evolving microbiota during Chouguiyu fermentation, and the volatile compounds and amino acids profiles were measured alongside with chemical characterization of the samples (e.g., determination of pH, TVB-N, TBARS, and TCA-soluble peptides). Based on the changes of the microbiota, the fermentation was categorized into two stages: early-fermentation, 1st-3rd days; and late-fermentation, 4th-7th days. Linalool, piperitone, anethole, 1-octen-3-ol, 2-methyl-3-octanone and indole were identified as characteristic volatile compounds in Chouguiyu. According to the sensory evaluation results, the flavor of the Chouguiyu was reinforced in the late-fermentation stage. Redundancy analysis showed the relationships between evolving microbiota and the formation of Chouguiyu's aroma and taste, and Psychrilyobacter was identified to be the most important bacterial genus contributing to flavor and aroma development, followed by Fusobacterium, Arcobacter and Oceanisphaera. These genera were positively correlated with Glu, Met, Tyr, Pro, linalool, piperitone, indole, TBARS, TVB-N, and TCA, and influenced the flavor and aroma of the Chouguiyu. The results of this study provided a scientific basis to further improve Chouguiyu production.

Three strains of lactic acid bacteria (LAB), including two strains of Lactobacillus plantarum and one strain of Lactococcus lactis isolated from spontaneously fermented Yucha, a traditional Chinese home-made fermented fish product, were evaluated as starter cultures for Yucha production. All three starter cultures could drive Yucha fermentation processes by rapid colonizing and fast acidifying the raw fish materials, and restricting the growth of undesirable bacteria. As a result, the starter-inoculated Yucha products were safer than their spontaneously-fermented counterpart, and fewer biogenic amines were detected in them. During the late stage of Yucha fermentation, the initial L. lactis was gradually replaced by endogenous L. plantarum, indicating that Yucha environmental condition is a favorable niche of L. plantarum. Volatile compounds profiling combined with cluster analysis demonstrated that the competition between the two species significantly shaped the development of aroma and flavor compounds in Yucha. Besides, correlation analysis suggested that 1-methyl-naphthalene could be a potential indicator to evaluate the degree of ripeness in Yucha products.