Diversity of bacteria and yeast in the naturally fermented cotton seed and rice beverage produced by Brazilian Amerindians

Abstract

Microorganisms associated with the fermentation of cotton seed and rice were studied using a combination of culture-dependent and -independent methods. Samples of the cotton seed and rice beverage were collected every 8 h during the fermentation process for analysis of the microbiota present over 48 h. The lactic acid bacteria (LAB) population reached values of approximately 8.0 log cfu/mL. A total of 162 bacteria and 81 yeast isolates were identified using polyphasic methods. LAB (Lactobacillus plantarum, Lactobacillus vermiforme, Lactobacillus paracasei) were the most frequently isolated bacteria. Bacillus subtilis was present from 16 h until the end of the fermentation process. A decrease in pH value from 6.92 (0 h) to 4.76 (48 h) was observed, and the concentration of lactic acid reached 24 g/L at the end of the fermentation process. DGGE (denaturing gradient gel electrophoresis) was performed to determine the dynamics of the communities of bacteria and yeast, and the analysis revealed a predominance of LAB throughout the fermentation process. No changes were observed in the yeast community. The yeast species detected were Candida parapsilosis, Candida orthopsilosis, Clavispora lusitaniae and Rhodotorula mucilaginosa. Our studies indicate that the DGGE technique combined with a culture-dependent method is required to discern the dynamics in the fermentation of cotton seed and rice.