Screening,Identification And Optimization Of Fermentation Conditions Of Pichia Pastoris Producing γ-Aminobutyric Acid

Gamma aminobutyric acid is a kind of non-protein amino acid, which exists widely in nature, and it has important physiological functions in the animal, such as lowering blood pressure, resisting anxiet, curing depression and so on. Gamma aminobutyric acid has been widely used in food and medicine, and it had became a hot research point.In this study, we used high performance liquid chromatography to determine the capacity of 42 strains of yeast to produce gamma amino acid, and a strain of higher yield of gamma aminobutyric acid was screened out, named as strain BDH29. The yield of gamma amino acid was 0.383g/L.The strain BDH29 was preliminarily identified as Pichia kudriavzevii by API 20 C AUX test, the strain could use D-glucose, glycerol, N-acetyl-glucoside, the rest saccharides could not be used. With a further study of strain BDH29, the gene sequence of 26S rDNA has obtained through molecular biology assay, and the lengths of it was 579bp. After homology analysis of strain BDH29, it was also identified as Pichia kudriavzevii, and the homology was 100%, this result was consistent with API test.Through the single factor experiment and orthogonal experiment to determine the optimum medium compositions of strain BDH29 for gamma aminobutyric acid yield were: glucose 3.0%, peptone 1.0%, yeast powder 1.0%, L-MSG 0.5%. The optimum fermentation conditions were:initial pH 7.0, inoculants size 4%, fermentation time 72h, fermentation temperature 28℃. After optimization of fermentation conditions, the yield of gamma aminobutyric acid produced by strain BDH29 has reached to 0.527g/L, and had been improved about 37.6% compared with the formal basic fermentation medium.