Insights into microbiota community dynamics and flavor development mechanism during golden pomfret(Trachinotus ovatus)fermentation based on single-molecule real-time sequencing and molecular networking analysis

Popular fermented golden pomfret(Trachinotus ovatus)is prepared via spontaneous fermentation;however,the mechanisms underlying the regulation of its flavor development remain unclear.This study shows the roles of the complex microbiota and the dynamic changes in microbial community and flavor compounds during fish fermentation.Single-molecule real-time sequencing and molecular networking analysis revealed the correlations among different microbial genera and the relationships between microbial taxa and volatile compounds.Mechanisms underlying flavor development were also elucidated via KEGG based functional annotations.Clostridium,Shewanella,and Staphylococcus were the dominant microbial genera.Forty-nine volatile compounds were detected in the fermented fish samples,with thirteen identified as characteristic volatile compounds(ROAV>1).Volatile profiles resulted from the interactions among the microorganisms and derived enzymes,with the main metabolic pathways being amino acid biosynthesis/metabolism,carbon metabolism,and glycolysis/gluconeogenesis.This study demonstrated the approaches for distinguishing key microbiota associated with volatile compounds and monitoring the industrial production of high-quality fermented fish products.

Changes in chemical composition,structural and functional microbiome during alfalfa(Medicago sativa)ensilage with Lactobacillus plantarum PS-8

Improving silage production by adding exogenous microorganisms not only maximizes nutrient preservation,but also extends product shelf life.Herein,changes in the quality and quantity of Lactobacillus plantarum PS-8(PS-8)-inoculated alfalfa(Medicago sativa)during silage fermentation were monitored at d 0,7,14,and 28(inoculum dose of PS-8 was 1105 colony forming units[cfu]/g fresh weight;50 kg per bag;10 bags for each time point)by reconstructing metagenomic-assembled genomes(MAG)and Growth Rate InDex(GRiD).Our results showed that the exogenous starter bacterium,PS-8 inoculation,became the most dominating strain by d 7,and possibly played a highly active role throughout the fermentation process.The pH value of the silage decreased greatly,accompanied by the growth of acidproducing microorganisms namely PS-8,which inhibited the growth of harmful microorganisms like molds(4.18 vs.1.42 log cfu/g)and coliforms(4.95 vs.0.66 log most probable number[MPN]/g).The content of neutral detergent fiber(NDF)decreased significantly(41.6%vs.37.6%;dry matter basis).In addition,the abundance and diversity of genes coding microbial carbohydrate-active enzymes(CAZymes)increased significantly and desirably throughout the fermentation,particularly the genes responsible for degrading starch,arabino-xylan,and cellulose.Overall,our results showed that PS-8 was replicating rapidly and consistently during early-and mid-fermentation phases,promoting the growth of beneficial lactic acid bacteria and inhibiting undesirable microbes,ultimately improving the quality of silage.