evaluation of alkaline protease production and optimization of culture medium by yarrowia lipolytica

 Introduction: Proteases are the most important industrial enzymes. These enzymes have gained much attention due to their industrial applications in eliminating the environmental pollutions and improving the industrial processes. The aims of this research were the isolation and identification of native yeasts that were able to produce the alkaline protease. Materials and methods: Several samples of soil, water and wastewater were collected from various places. The culture media used for screening of yeast spp. with potential of alkaline protease production were alkaline peptone agar and alkaline milk agar. The alkaline protease activity in potential spp. was measured using Lowry method. The effects of different culture media on the production of alkaline protease by selected yeast isolates were determined. For molecular identification of the best isolate, the DNA extraction was performed and the PCR followed using universal 18s rDNA primers. Results: Among 27 isolates with the capability of alkaline protease production, one isolate with the most enzyme activity, 525 u/ ml, was selected for further processing. The best culture medium for alkaline protease production was YPG broth. The comparison of 18s rDNA sequence from isolated yeast with the highest enzyme activity, with the genomic database available in Gen Bank, using BLAST software showed that our yeast isolate had the highest similarity with Yarrowia lipolytica. Discussion and conclusion: According to numerous applications of alkaline proteases industrially and the lack of their production in our country, the native strains could be beneficial for their production. Regarding to non-pathogenicity and high productivity of alkaline protease by our isolated yeast, Yarrowia lipolytica, this isolate could be introduced as an amenable strain for industrial production of alkaline protease.