Efficient production of gamma ‐aminobutyric acid by engineered Saccharomyces cerevisiae with glutamate decarboxylases from Streptomyces

This study was aimed to establish an efficient food‐grade production process of GABA by engineeringSaccharomyces cerevisiae that is generally recognized as safe (GRAS). GABA can be produced by catalytic decarboxylation of L ‐glutamate (L‐Glu) by glutamate decarboxylase (GAD, EC4.1.1.15). Two GADs, SsGAD fromStreptomyces sp. MJ654 ‐NF4 and ScGAD fromStreptomyces chromofuscus ATCC 49982, were heterologously expressed inS. cerevisiae BJ5464. The engineeredyeast strians were used as whole ‐cell biocatalysts for GABA production.S. cerevisiae BJ5464/SsGAD exhibited significantly higher efficient catalytic activity than that ofS. cerevisiae BJ5464/ScGAD. The optimal bioconversion system consisted of a cell density of OD600 30, 0.1  M L‐Glu, 0.28 mM pyridoxal phosphate in 0.2 M Na2HPO4‐citric acid buffer with pH 5.4, and the reactions were performed at 50 °C for 12 h.S. cerevisiae BJ5464/SsGAD cells can be reused and the accumulated GABA titer reached 62.6  g/L after 10 batches with an overall molar conversion rate of 60.8 mol%. This work thus provides an effective production process of GABA using engineered yeast for food and pharmaceutical applications. TwoStreptomyces glutamate decarboxylases were successfully reconstituted inSaccharomyces cerevisiae The engineered yeast strain,S. cerevisiae/SsGAD, was used as an efficient whole ‐cell biocatalyst for GABA production The conditions for bioconversion of L‐glutamate to GABA byS. cerevisiae/SsGAD were optimi...
Source: Biotechnology and Applied Biochemistry - Category: Biochemistry Authors: Tags: Original Article Source Type: research