Screening of yeasts from Brazilian Amazon rain forest for extracellular proteinases production.

Eighty seven yeast strains representing 34 species isolated from Parahancornia amapa fruit and associated Drosophila flies collected in the Brazilian Amazon rain forest, were screened for proteinase production. Proteolytic activity was tested through casein hydrolysis in solid medium supplemented with 0.5% casein and glucose. Among 23 strains, 18 from genus Candida and 5 from Pichia were caseinolytic and produced proteinases in yeast carbon base liquid medium supplemented with casein 0.01%. The proteolytic activity was tested on pH ranging from 2.0 to 9.0 in correspondence to the pH of the cultures media in which the yeasts were grown. Six highly proteolytic strains: Candida parapsilosis AP153A, C. krusei AP176, C. sorbosa DR215, C. sorbosa AP259, C. valida AP209A and C. sorboxylosa AP287 were selected and the pH optima of production and the proteolytic activity were determined. In general the secretion of proteinase was maximum throughout the exponential and the stationary phases. Greater production occurred in acidic culture and high activity was observed at pH 3.0, 4.0 and 5.0.