BACKGROUNDThe poly--glutamic acid (-PGA) hydrolase of PgdS affects the molecular weight and yield of -PGA in Bacillus subtilis, while the effects of PgdS on the -PGA synthesis in Bacillus licheniformis have not been investigated. RESULTSBy heterologous expression in Escherichia coli, the PgdS was characterized. The purified PgdS had an optimal -PGA degradation activity from pH 5.5 to 6.5, with an appropriate reaction temperature from 37 degrees C to 45 degrees C. The enzyme activity could be enhanced by Zn2+, Mn2+, Ca2+ and SDS, while inhibited by Hg2+ or Cu2+. By enhanced expression of pgdS gene in vivo, the enzyme activity, protein concentration and gene transcriptional level of PgdS were improved, and -PGA molecular weight decreased from 1000-1200 kDa to 600-800 kDa. Moreover, the -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--glutamate synthetase were confirmed to be improved, which might be the reason for the increased -PGA production. CONCLUSIONEnhanced expression of pgdS gene in B. licheniformisWX-02 helped to reduce the molecular weight and improve the yield of -PGA. This study provided a novel strategy to regulate the molecular weight and yield of -PGA. (c) 2013 Society of Chemical Industry