Screening of Yeast with High Protease Activities from Traditional Yogurt and Optimization of Enzyme Conditions

Abstract:

The strains of protease yeasts were isolated from the traditional fermented yoghurt of Xinjiang Kazak and ensure the protease activity. The protease activity was screened plates and shake flask fermentation，as the index. Five strains of high-yield protease were obtained and optimization of enzymological conditionswere studied preliminarily. The results of morphological observation and 26S rDNA sequence analysis indicated that D1-3 was Pichia kudriavzevii，E1-5 was Issatchenkia orientalis，S1-7 was Kluyveromyces marxianus，W1-10 was Candida parapsilosis and S1-16 was Saccharomyces cerevisiae. Optimizing the conditions of producing enzymes，the strains D1-3 the highest protease activity of fermentation broth was reached to 78 U/mL、S1-7 was reached to 79 U/mL、S1-16 was reached to 55 U/mL、E1-5 was reached to 82 U/mL、W1-10 was reached to 64 U/mL，we can indicated that the most proper temperature of all strains were 28 ℃ with one exception of W1-10 was 37 ℃；The initial pH，inoculation amount of strain and incubation time were 5.0，3%，48h，respectively，in that case，enzyme production reached the best.