Enhanced expression of pgdS gene for high production of poly‐γ‐glutamic aicd with lower molecular weight in Bacillus licheniformisWX‐02

BACKGROUND The poly‐γ‐glutamic acid (γ‐ PGA ) hydrolase of PgdS affects the molecular weight and yield of γ‐ PGA in Bacillus subtilis , while the effects of PgdS on the γ‐ PGA synthesis in Bacillus licheniformis have not been investigated. RESULTS By heterologous expression in Escherichia coli , the PgdS was characterized. The purified PgdS had an optimal γ‐ PGA degradation activity from pH 5.5 to 6.5, with an appropriate reaction temperature from 37 °C to 45 °C. The enzyme activity could be enhanced by Zn 2+ , Mn 2+ , Ca 2+ and SDS , while inhibited by Hg 2+ or Cu 2+ . By enhanced expression of pgdS gene in vivo , the enzyme activity, protein concentration and gene transcriptional level of PgdS were improved, and γ‐ PGA molecular weight decreased from 1000–1200 kDa to 600–800 kDa . Moreover, the γ‐ PGA yield reached 20.16 g L ‐1 , increased by 54% than the native strain (13.11 g L −1 ). Gene transcript levels of glutamate transporters and poly‐γ‐glutamate synthetase were confirmed to be improved, which might be the reason for the increased γ‐ PGA production. CONCLUSION Enhanced expression of pgdS gene in B. licheniformis WX ‐02 helped to reduce the molecular weight and improve the yield of γ‐ PGA . This study provided a novel strategy to regulate the molecular weight and yield of γ‐ PGA .