Efficacy and mechanisms of rotating algal biofilm system in remediation of soy sauce wastewater

This study investigated the efficacy of the rotating algal biofilm (RAB) for treating soy sauce wastewater (SW) and its related treatment mechanisms. The RAB system demonstrated superior nutrient removal (chemical oxygen demand, ammonium nitrogen, total nitrogen, and phosphorus for 92 %, 94 %, 91 %, and 82 %, respectively) and biofilm productivity (14 g m-2 d-1) at optimized 5-day harvest time and 2-day hydraulic retention time. This was mainly attributed to the synergistic interactions within the algae-fungi (Apiotrichum)-bacteria (Acinetobacter and Rhizobia) consortium, which effectively assimilated certain extracellular polymeric substances into biomass to enhance algal biofilm growth. Increased algal productivity notably improved protein and essential amino acid contents in the biomass, suggesting a potential for animal feed applications. This study not only demonstrates a sustainable approach for managing SW but also provides insight into the nutrient removal and biomass conversion, offering a viable strategy for large-scale applications in nutrient recovery and wastewater treatment.

Identification and control of gas-producing bacteria isolated from the swollen bagged soy sauce

The swelling of soy sauce bags seriously affects product quality and causes food safety problems, which has become an urgent problem to solve in the condiment industry. Here, gas-producing bacteria in the swollen bagged soy sauce were isolated and identified to provide an effective control method for inhibiting their growth and solving the swelling of soy sauce bags. It was found that three gas-producing bacteria isolated from the swollen bagged soy sauce were confirmed as Bacillus amyloliquefaciens (G1), Bacillus sp. (G2) and Bacillus subtilis (P3) using 16S rDNA analysis. The strains' morphologies, growth rates, and physiological and biochemical characteristics were also compared. Further studies yielded the optimal growth time, temperature and pH for the three gas-producing bacteria (B. amyloliquefacien: 24 h, 37 °C, and pH 7; Bacillus sp.: 18 h, 30 °C, and pH 6.5-7.5; B. subtilis: 36 h, 30 °C, and pH 8). Bacillus sp. was more salt tolerant than the other two. Then the antibacterial effect of the combination was tested by the physicochemical index. The results showed that filtering through a 0.22 μm inorganic micro-filtration membrane, sterilizing at 121 °C for 2 min, and adding 1 g/kg potassium sorbate was effective methods to inhibit three gas-producing bacteria and control the swelling of soy sauce.

Fermentation of high-salt liquid-state soy sauce without any additives by inoculation of lactic acid bacteria and yeast

Food additives are artificial or natural substances that are added to food to improve the color, aroma, taste, and other qualities, and to meet processing requirements. For the concern of food health and safety, brewed soy sauce without additives has attracted consumers' attention. Here, only four necessary raw materials including soybean, wheat, salt, and water were added. High-salt soy sauce fermentation was conducted for six months by sequential inoculation of lactic acid bacteria and yeast under different brine content (18%, 20%, and 22%). By analyzing the physicochemical indicators during moromi, three soy sauces (No. 1: 18% salt, inoculated with Tetragenococcus halophilus and Zygosaccharomyces rouxii, No. 5: 20% salt, inoculated with T. halophilus and Z. rouxii, No. 11: 22% salt, inoculated with T. halophilus and Candida versatilis) were selected and sterilized to produce finished products for further comparative investigation. Results showed that the flavor components of these three soy sauces were richer in variety than the commercial soy sauces and No. 11 soy sauce was detected to have the largest total amount of organic acids. Plate count agar analysis revealed that the free amino acid differences of soy sauces were distinct, among which the No. 11 soy sauce had the highest glutamate content of 19.64 g L^-1. Besides, it was found that the shelf life of these three soy sauces could reach two years at 4 ℃. This study suggests that the high-salt soy sauce made by rational application of lactic acid bacteria, yeast, and effective sterilization can have high quality and long shelf life without adding any additives.

Fathoming Aspergillus oryzae metabolomes in formulated growth matrices

The stochasticity of Aspergillus oryzae (Trivially: the koji mold) pan-metabolomes commensurate with its ubiquitously distributed landscapes, i.e. growth matrices have been seemed uncharted since its food fermentative systems are mostly being investigated. In this review, we explicitly have discussed the likely tendencies of A. oryzae metabolomes pertaining to its growth milieu formulated with substrate matrices of varying nature, composition, texture, and associated physicochemical parameters. We envisaged typical food matrices, namely, meju, koji, and moromi as the semi-natural cultivation models toward delineating the metabolomic patterns of the koji mold, which synergistically influences the organoleptic and functional properties of the end products. Further, we highlighted how tailored conditions in sub-natural growth matrices, i.e. synthetic cultivation media blends, inducers, and growth surfaces, may influence A. oryzae metabolomes and targeted phenotypes. In general, the sequential or synchronous growth of A. oryzae on formulated matrices results in a number of metabolic tradeoffs with its immediate microenvironment influencing its adaptive and regulatory metabolomes. In broader context, evaluating the metabolic plasticity of A. oryzae relative to the tractable variables in formulated growth matrices might help approximate its growth and metabolism in the more complex natural matrices and environs. These approaches may considerably help in the design and manipulation of hybrid cultivation systems towards the efficient harnessing of commercial molds.

Comparative Genomics of Lactobacillus acidipiscis ACA-DC 1533 Isolated From Traditional Greek Kopanisti Cheese Against Species Within the Lactobacillus salivarius Clade

Lactobacillus acidipiscis belongs to the Lactobacillus salivarius clade and it is found in a variety of fermented foods. Strain ACA-DC 1533 was isolated from traditional Greek Kopanisti cheese and among the available L. acidipiscis genomes it is the only one with a fully sequenced chromosome. L. acidipiscis strains exhibited a high degree of conservation at the genome level. Investigation of the distribution of prophages and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) among the three strains suggests the potential existence of lineages within the species. Based on the presence/absence patterns of these genomic traits, strain ACA-DC 1533 seems to be more related to strain JCM 10692^T than strain KCTC 13900. Interestingly, strains ACA-DC 1533 and JCM 10692^T which lack CRISPRs, carry two similar prophages. In contrast, strain KCTC 13900 seems to have acquired immunity to these prophages according to the sequences of spacers in its CRISPRs. Nonetheless, strain KCTC 13900 has a prophage that is absent from strains ACA-DC 1533 and JCM 10692^T. Furthermore, comparative genomic analysis was performed among L. acidipiscis ACA-DC 1533, L. salivarius UCC118 and Lactobacillus ruminis ATCC 27782. The chromosomes of the three species lack long-range synteny. Important differences were also determined in the number of glycobiome related proteins, proteolytic enzymes, transporters, insertion sequences and regulatory proteins. Moreover, no obvious genomic traits supporting a probiotic potential of L. acidipiscis ACA-DC 1533 were detected when compared to the probiotic L. salivarius UCC118. However, the existence of more than one glycine-betaine transporter within the genome of ACA-DC 1533 may explain the ability of L. acidipiscis to grow in fermented foods containing high salt concentrations. Finally, in silico analysis of the L. acidipiscis ACA-DC 1533 genome revealed pathways that could underpin the production of major volatile compounds during the catabolism of amino acids that may contribute to the typical piquant flavors of Kopanisti cheese.

Dynamics of microbial community during the extremely long-term fermentation process of a traditional soy sauce

BACKGROUND

Soy sauce produced by long-term natural fermentation is a traditional specialty in Asia, with a reputation for superior quality and rich flavour. In this study, both culture-dependent and culture-independent approaches were used to investigate the microbial diversity and community dynamics during an extremely long-term (up to 4 years) natural fermentation of Xianshi Soy Sauce, a national intangible cultural heritage.

RESULTS

Genera of Bacillus, Aspergillus and Cladosporium were detected by both methods above. The relative abundance of the genera Bacillus and Weissella was significantly higher in the late stage than in the early one, while the genera Klebsiella and Shimwellia were opposite (P < 0.05). For microbial community structure, subsequent analyses showed that obvious changes occurred with fermentation time, while there was a fair homogeneousness among samples of the same year, especially during the late fermentation stage.

CONCLUSIONS

The clustering analysis tended to separate the fermented mashes of the 4th year from the earlier stages, suggesting the necessity of the long fermentation period for developing distinctive microbiota and characteristic quality-related compounds. This is the first report to explore the temporal changes in microbial dynamics over a period of 4 years in traditional fermentation of soy sauce, and this work illustrated the importance of isolation of appropriate strains to be used as starter cultures in brewing processes. © 2016 Society of Chemical Industry.