Screening of Lactiplantibacillus plantarum with High Stress Tolerance and High Esterase Activity and Their Effect on Promoting Protein Metabolism and Flavor Formation in Suanzhayu, a Chinese Fermented Fish

Microbial interactions between Lactoplantibacillus plantarum and Rhodotorula mucilaginosa in the fermented fish juice system

Lactic acid bacteria and yeasts play important roles in fermented fish products. The present study investigated the interaction between Lactoplantibacillus plantarum and Rhodotorula mucilaginosa in a fermented fish juice system. The results demonstrated that the co-culture of L. plantarum L6 and R. mucilaginosa Y9 significantly increased the maximum specific growth and population of L. plantarum L6, and decreased the lag phase. During microbial interactions, R. mucilaginosa Y9 increased the concentration of soluble proteins and provided L. plantarum L6 with more TCA-soluble peptides. Additionally, these two strains showed co-metabolism of amino acids, such as glutamic acid and aspartic acid. Furthermore, the microbial interaction between two strains influenced the generation of volatile compounds. R. mucilaginosain Y9 removed some fishy-odors compounds, including 1-Octen-3-ol, 1-Hexanol and phthalate esters, but increased the accumulation of aldehyde compounds with unpleasant odors. In addition, co-cultivation promoted the generation of special compounds, such as γ-dodecalactone and 2-pentylfuran, which could improve the flavor quality of fermented fish products.

Integrating metabolite profiles and macrotranscriptomics to explore the flavor improvement mechanisms of fermented oyster hydrolysates with endogenous microbe (Lactobacillus pentosus) inoculation

The study investigates the impacts of indigenous bacterial strains inoculation specifically L. pentosus, on the flavor characteristics, microbial composition, and metabolite profiles of fermented oyster hydrolysates. This research aimed to elucidate potential mechanisms underlying the reduction of off-flavors in fermented hydrolysates. A total of 46 and 57 volatile compounds were detected by GC-MS and GC-IMS in hydrolysates inoculated with different core microbes, respectively. The 9 key volatile compounds detected by GC-MS analysis. (E, E)-2,4-heptadienal, heptanal, octanal, pentanal, and (E)-2-octenal reduced the off-flavor of the fermented oyster hydrolysate. Meanwhile 1-octen-3-ol, 3-octanone, 4-octanone, and (E, Z)-2,6-nonadienal enhanced the direct contribution of desirable flavors. Variation in 16 amino acids, 10 organic acids and 3 nucleotides were monitored to further understand the metabolic changes affecting flavor quality. Moreover, pyruvate decarboxylase [EC 4.1.1.1], phosphomannanase [EC 3.2.1.109], lipoyl-CoA synthetase [EC 6.3.2.4], and arginine kinase [EC 2.7.3.3] were the main microbiologically active enzymes. An increase in the content of aromatic compounds and a decrease in the content of C6-C9 unsaturated aldehydes through Lys, Phe, Asp, Glu, phosphoenolpyruvate, oleic acid, and linoleic acid metabolism pathways improved the flavor of oyster hydrolysates fermented by L. pentosus. This research provides a theoretical basis for leveraging autochthonous microbial fermentation to systematically improve flavor characteristics in fermented products.

Optimization of α-L-arabinofuranosidase CcABF on clarification and beneficial active substances in fermented ginkgo kernel juice by artificial neural network and genetic algorithm

This study aimed at using α-L-arabinofuranosidase CcABF to improve the clarity and active substances in fermented ginkgo kernel juice by artificial neural network (ANN) modeling and genetic algorithm (GA) optimization. A credible three-layer feedforward ANN model was established to predict the optimal parameters for CcABF clarification. The experiments proved the highest transmittance of 89.40% for fermented ginkgo kernel juice with this understanding, which exhibited a 25.56% increase over the unclarified group. With the clarification of CcABF, the antioxidant capacity in juice was enhanced with the increase of total phenolic and flavone contents, and the maximum DPPH and hydroxyl radical scavenging rates were increased by 89.71% and 26.65%, respectively. The contents of toxic ginkgolic acids declined markedly, while the active ingredients of ginkgetin and ginkgolide B showed a modest increase. Moreover, changes in free amino acids and volatile compounds improved the nutritive value and flavor of clarified fermented ginkgo kernel juice.

Inoculation of Yarrowia lipolytica promotes the growth of lactic acid bacteria, Debaryomyces udenii and the formation of ethyl esters in sour meat

Yarrowia lipolytica N12 and A13 with high lipase activity obtained by mutagenesis were inoculated into sour meat, and their effects on physicochemical properties, microbial community succession, free amino acids, and volatile compounds of sour meat were investigated. Inoculation fermentation increased the contents of free amino acids observably, rapidly reduced pH, promoted the accumulation of total acids, decreased 2-thiobarbituric acid reactive substances (TBARS) values. In addition, the addition of Y. lipolytica might contribute to the growth of lactic acid bacteria, Candida spp., and Debaryomyces udenii, which play an important role in production of volatile compounds. It was shown that inoculation promoted the production of esters, aldehydes, and alcohols, especially ethyl esters, giving sour meat a better meat flavor. Besides, it was found that Y. lipolytica A13 had better fermenting property. Sample of A13 group had higher contents of ethyl esters, free amino acids and dominant microorganisms. The results may help to provide new strains for sour meat fermentation.

Transforming the fermented fish landscape: Microbiota enable novel, safe, flavorful, and healthy products for modern consumers

Regular consumption of fish promotes sustainable health while reducing negative environmental impacts. Fermentation has long been used for preserving perishable foods, including fish. Fermented fish products are popular consumer foods of historical and cultural significance owing to their abundant essential nutrients and distinct flavor. This review discusses the recent scientific progress on fermented fish, especially the involved flavor formation processes, microbial metabolic activities, and interconnected biochemical pathways (e.g., enzymatic/non-enzymatic reactions associated with lipids, proteins, and their interactions). The multiple roles of fermentation in preservation of fish, development of desirable flavors, and production of health-promoting nutrients and bioactive substances are also discussed. Finally, prospects for further studies on fermented fish are proposed, including the need of monitoring microorganisms, along with the precise control of a fermentation process to transform the traditional fermented fish to novel, flavorful, healthy, and affordable products for modern consumers. Microbial-enabled innovative fermented fish products that consider both flavor and health benefits are expected to become a significant segment in global food markets. The integration of multi-omics technologies, biotechnology-based approaches (including synthetic biology and metabolic engineering) and sensory and consumer sciences, is crucial for technological innovations related to fermented fish. The findings of this review will provide guidance on future development of new or improved fermented fish products through regulating microbial metabolic processes and enzymatic activities.

Influence of Lactobacillus helveticus ZF22 and TR1-1-3 strains on the aromatic flavor of fermented sausages

In this study, five strains isolated from traditional Inner Mongolian air-dried meat products were used, two Lactobacillus helveticus strains, ZF22 and TR1-1-3, with potent antibacterial activity, acid, salt, and nitrite tolerance, were selected for this study. Lactic acid bacteria (LAB) (Lactobacillus helveticus ZF22 and TR1-1-3) were inoculated into fermented sausages at 10⁷ CFU/g and their volatiles were studied during fermentation and storage. Clustering heat map and principal component analysis (PCA) were used to identify differentiating flavor components in uninoculated and inoculated sausages. The results showed that 72 volatile flavor substances were identified during the fermentation of the fermented sausages and that inoculation with Lactobacillus helveticus ZF22 and TR1-1-3 increased the proportion of acids, ketones and alkanes. Moreover, the clustering heat map demonstrated that esters such as ethyl isobutyrate, ethyl acetate, and ethyl valerate were more abundant in TR1-1-3 and ZF22 than ZR. The PCA analysis showed that the volatile compounds of the three fermented sausages were distributed in separate quadrants, suggesting that the volatile compound compositions of the three fermented sausages differed significantly. Our findings suggest that inoculating fermented sausages with Lactobacillus helveticus TR1-1-3 and ZF22 can improve flavor by enhancing the type and amount of flavor compounds.

Effect of Autochthonous Lactic Acid Bacteria-Enhanced Fermentation on the Quality of Suancai

The lactic acid bacteria (LABs) used for fermentation have an extremely vital impact on the quality of Suancai, a fermented vegetable. The bacterial diversity and metabolites of inoculated Suancai with LABs, including Lactiplantibacillus plantarum (Lb. plantarum), Levilactabacillus brevis (Lb. brevis), and Leuconostoc mesenteroides (Leu. mesenteroides), were investigated. The inoculation of LABs significantly decreased the pH and the content of nitrite. The Suancai inoculated with LABs had a higher content of the total titratable acidity (TTA) and organic acids than spontaneous fermentation. The LABs inoculation significantly influenced the bacterial community structures, which directly or indirectly caused changes of metabolites. The bacterial community profiles of Suancai inoculated with Lb. plantarum were more similar to spontaneous fermentation. The inoculation of Lb. plantarum, Lb. brevis, and Leu. mesenteroides could increase its abundance in Suancai. Whatever the species inoculated, Lb. plantarum was always the predominant bacterium in Suancai after fermentation. The inoculated LABs were positively correlated with most volatile compounds and amino acids. The inoculated LABs significantly improved the volatile compounds and amino acid content of Suancai. This study could contribute to understanding the function of starters in Suancai fermentation and promote the selection of applicable starters for high-quality Suancai production.