Lactobacillus fermentum as a new inhibitor to control advanced glycation end-product formation during vinegar fermentation

The inhibitory activity of lactic acid bacteria(LAB)toward advanced glycation end-products(AGEs)during vinegar fermentation was studied,and its relationships with the substrate consumption,antioxidant capacity,total phenolic content,total flavonoid compounds,α-glucosidase,andα-amylase activity inhibition were evaluated.The vinegar was made from rice powder flour by liquid-state fermentation(LSF).The selected LAB strains were separately co-cultivated with Saccharomyces cerevisiae and Acetobacter pasteurianus 1.41 in alcoholic and acetic acid fermentation,respectively.Among 3 strains,Lactobacillus fermentum showed the strongest inhibitory effect on the formation of total fluorescent AGEs and carboxymethyl lysine(CML)/carboxyethyl lysine(CEL)in the fermentation process.The corresponding mechanisms included the acceleration of substrate consumtion,improvement of antioxidant activities,and inhibition ofα-glucosidase andα-amylase.In addition,the fluorescent AGEs and the CML/CEL were negatively correlated with the antioxidant activities,while theα-glucosidase andα-amylase activities were positively correlated with the total phenols and total flavonoids.Moreover,the variety of main flavor compounds increased,including esters,alcohols,phenols and acids.The results of the study support the potential use of screened LAB strains to inhibit the formation of fluorescent AGEs,CML and CEL on fermented products and in the food processing industry,without associated risks to consumers.

Changes and correlation of microorganism and flavor substances during persimmon vinegar fermentation

To investigate the microbial diversity and the change of the flavor substances during the traditional natural persimmon vinegar fermentation,two group samples from alcohol fermentation stage(A)and acetic acid fermentation stage(B)were analyzed.The results showed that Burkholderia,Lactobacillus,Acetobacter,Komagataeibacter were the main bacteria,and the major fungi were Saccharomyces,Hanseniaspora,Hortaea,and Cladosporium at the genus level.The contents of flavonoids and polyphenols in B increased by 17.91%and 26.59%compared with A,respectively.The superoxide anion scavenging activity significantly increased by 20.15%.The contents of total free amino acids were 5709.99±410.36 mg/L and 5736.16±472.02 mg/L,and the total contents of 9 organic acids were 19.89±1.20 g/L and 33.77±2.49 g/L in samples A and B,respectively.Pearson correlation analysis showed that 11 flavor compounds were related to Lactobacillus and Leuconostoc;8 and 10 compounds were respectively related to Komagataeibacter and Acetobacter;13 and 19 flavor compounds were respectively associated with Saccharomyces and Monascus.Orthogonal Partial Least Square(OPLS)model showed that the contents of Leu,Lys,and lactic acid were mainly associated with fungi,andγ-aminobutyric acid(GABA)content was correlated with Lactobacillus,Acetobacter,Leuconostoc,and Saccharomyces.This study revealed the relationship between microbial diversity and flavor compounds in persimmon vinegar produced by spontaneous fermentation.The results can provide a theoretical support for the safety and health assessment of persimmon vinegar.