Chicha, a type of beer made mainly with maize or cassava, is a traditional fermented beverage of the Andean region. There have only been a few studies on yeasts associated with chicha fermentation, and the species diversity occurring during the production of this beverage is not known. The objective of this study was to determine the biodiversity of yeasts in chicha, and to characterize the Saccharomyces cerevisiae populations associated with the production of chicha de jora, seven-grain chicha, chicha de yuca, and chicha de morocho in Ecuador. The molecular diversity of S. cerevisiae populations was determined by restriction polymorphism mitochondrial profiles. The beverages were characterized based on their physicochemical parameters. Twenty-six species were identified, and the most prevalent species were S. cerevisiae and Torulaspora delbrueckii. Other yeast species were isolated at low frequencies. Among 121 isolates of S. cerevisiae, 68 different mtDNA molecular profiles were identified. These results showed that chichas are fermented by a high number of different strains of S. cerevisiae. Some other species provided a minor contribution to the fermentation process. The chicha presented generally similar physicochemical parameters to those observed for other traditional fermented beverages, and can be considered as an acid fermented beverage.

Production of xylanolytic enzymes by an Aspergillus niger CCMI 850 isolate was investigated in batch cultures. The effect of the composition of a fermentation medium that did not include chemical inducers, on beta-xylanase, beta-xylosidase, alpha-L-arabinofuranosidase, and total cellulase activity was studied. With 4% xylan as the carbon source, about 65 U/mL of beta-xylanase was obtained, whereas the total cellulase activity was undetectable, under the specified conditions. This beta-xylanase activity represents the highest reported for a wild-type strain of A. niger. The effect of pH and temperature on the activity of beta-xylanase was studied. Partial characterization of the beta-xylanase showed that with insoluble birchwood as substrate the Km and Vmax were 0.3 mM and 19 mumol/min, respectively. Aspects of using the crude beta-xylanase preparation for applications in the pulp and paper industry were discussed.