Microbiological and physicochemical characterisation of caxiri, an alcoholic beverage produced by the indigenous Juruna people of Brazil

Abstract

Caxiri is a traditional fermented alcoholic beverage produced from cassava and sweet potatoes by the indigenous Juruna or Yudjá people in Brazil. Our results showed that caxiri fermentation is invariably associated with the following: (i) an increase in the total microbial population, with yeast being the largest group detected; (ii) a decrease in reducing sugars, malic, tartaric, succinic, oxalic and propionic acid; and (iii) a final product characterised by a high content of ethanol and a high concentration of lactic acid. The microbial community dynamics were investigated by culture-based and culture-independent approaches. Fermentation was assisted by a complex microbial community that changed in structure and composition during the fermentative process. The bacterial population ranged from 3.05 to 5.33 log/mL, and the yeast population varied from 3.27 log CFU/mL to 7.34 log CFU/mL, showing that yeasts dominated the fermentation process after 48 h. A total of 343 colonies of bacteria and 205 colonies of yeasts were isolated and initially grouped by Amplified Ribosomal DNA Restriction Analysis (ARDRA) and by biochemical features. Phylogenetic analysis of the 16S rRNA gene sequences of representative isolates showed that the bacteria were mainly represented by endospore-forming low-G + C content Gram-positive bacilli (Bacillus spp.; 61.5% of the isolates), with Bacillus pumilus, Bacillus spp. (Bacillus cereus group), and Bacillus subtilis being the main species identified. The species Sphingomonas sp. and Pediococcus acidilactici were also found. The dominant yeast identified was Saccharomyces cerevisiae. Rhodotorula mucilaginosa, Pichia membranifaciens, Pichia guilliermondii and Cryptococcus luteolus were also found. According to the Polymerase Chain Reaction and Denaturing Gradient Gel Electrophoresis (PCR–DGGE) analysis, the microbial communities present during fermentation were probably from the raw materials, ambient or present on the utensils used during beverage preparation. The results indicated the necessity to combine both culture-dependent and culture-independent methods for a better description of the microbial communities in indigenous starch fermentations. Also, pH values decreased from 4.76 to 3.15 during fermentation. The ethanol concentration was 83.9 g/L and lactic acid reached 27.89 g/L by the end of the fermentation process.