Quorum-sensing related promoter srfA (P-srfA) was used to construct autoinducible expression system for production of recombinant proteins in Bacillus subtilis. PsrfA was prominent in the unique property of inducer-free activity that is closely correlated with cell density. Here, using green fluorescent protein (GFP) as the reporter protein, P-srfA was optimized by shortening its sequences and changing the nucleotides at the conserved regions of 35 15 and 10 regions, obtaining a library of P-srfA derivatives varied in the strength of GFP production. Among all the promoter mutants, the strongest promoter P10 was selected and the strength in GFP expression was 150% higher than that of P-srfA. Heterologous protein of aminopeptidase and nattokinase could be overexpressed by P10, the activities of which were 360% and 50% higher than that of P-srfA, respectively. These results suggested that the enhanced promoter P10 could be used to develop autoinducible expression system for overexpression of heterologous proteins in B. subtilis. (C) 2016 Published by Elsevier Inc.