Search

To investigate the effect of fungal elicitors on biosynthesis of natamycin in the cultures of Streptomyces natalensis HW-2, the biomass and filtrate of the broth from Aspergillus niger AS 3.6472, Penicillium chrysogenum AS 3.5163, A. oryzae AS 3.2068, and Saccharomyces cerevisiae AS 2.2081 were used to induce natamycin production in S. natalensis HW-2. The results showed that the biomass of P. chrysogenum AS 3.5163 could enhance the yield of natamycin from 0.639 to 0.875 g l. The elicitor from the fermentation broth of P. chrysogenum AS 3.5163 showed the highest inducing efficiency with the yield of natamycin enhanced from 0.632 to 1.84 g l. The elicitor that was cultured for 2 days showed the strongest inducing activity during the fermentation of S. natalensis HW-2 for 24 h, and the yield of natamycin was enhanced from 0.637 to 2.12 g l. The biochemical parameters were examined at the end of fermentation and the results demonstrated that both the growth of cells and the concentration of residual sugar could be influenced. The residual sugar decreased from 5.03 to 4.27 g l, and the biomass decreased from 10.26 to 6.87 g l. Finally, the elicitor was identified as a low molecular weight substance with a similar polarity to that of butyl alcohol by primary qualitative analysis. [ABSTRACT FROM AUTHOR]

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, and γ-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. [Display omitted] • Illustrating the microbial diversity in the spontaneous persimmon vinegar fermentation at different fermentation stage. • Studying the change of flavonoids, polyphenols, antioxidant capacity and related flavor substances. • Revealing the relationship between the microbial diversity and flavor metabolites in the persimmon vinegar fermentation. [ABSTRACT FROM AUTHOR]

Nitrogen is an essential element for the growth and metabolism of Saccharomyces cerevisiae , and has a great impact on the quality of cider. In this study, the effects of organic nitrogen addition at different stages of fermentation process on the quality of cider were systematically explored. The main projects included the analysis of fermentation rate, yeast growth, organic acids, amino acids, and volatile aroma compounds. The results indicated that organic nitrogen addition speeded up fermentation rate and shortened fermentation time. The organic nitrogen addition before fermentation and at the early stationary phase altered the composition of organic acids in cider. Moreover, with the addition of organic nitrogen at three stages of fermentation (pre-fermentation, logarithmic and stable phases of yeast growth), the total concentrations of volatile aroma substances in ciders were 10.57 mg/L, 11.97 mg/L and 11.05 mg/L respectively, which were all significantly higher than that in control group (9.69 mg/L). A close relationship between free amino acids consumed during fermentation and volatile aroma compounds produced was revealed by partial least-squares regression analysis. Overall, this study provided a new strategy for cider quality improvement by evaluating the effects of organic nitrogen on the aroma composition of cider. [Display omitted] • Organic nitrogen accelerated fermentation rate and shortened fermentation time. • Volatile acids were greatly affected by the addition time of organic nitrogen. • The addition of organic nitrogen during fermentation enriched the types of esters. • Lysine and methionine were mostly used for synthesis of volatile aroma substances. [ABSTRACT FROM AUTHOR]