P9: Screening and selection of wild strains of fermentative yeast from unusual and extreme environments from Mexico

A collection of 342 yeast strains has been obtained using endemic and unique sources of fruit juices, industrial syrups, honey, cheese whey and other carbohydrate rich, natural and made made, products or by-products from Mexico. Three selective isolation media were used for their isolation. A primary selection was made based on their osmotolerance, and on their ability to produce either biomass, acid or ethanol from specific carbon sources. 

After evaluation of growth at 10, 40 and 60% w/w sugar concentration in a specifically designed plate medium, the strains were grown in Yeast Fermentation Medium (YFM), added with a specific carbon source at a concentration of either 10 or 20% w/w (glucose, sucrose, lactose, galactose, inulin, xylose, maltose, arabinose and mannose). Fermentation and acid production were evaluated in both solid and liquid media. Selected strains with high catabolic activity were tested under laboratory fermentation conditions, to detect desirable fermentation patterns and catabolic products by HPLC. Osmotolerant, ethanol and organic acid producing strains, were detected, which provided for unusual catabolic abilities. Proposed biotechnological applications for selected strains are presented and discussed.