Production enhancement of the extracellular lipase LipA in Bacillus subtilis: Effects of expression system and Sec pathway components.

Lipases are among the most versatile biocatalysts, and are used in a range of industrially relevant bioconversion reactions. However, the production of LipA in recombinant Bacillus subtilis is still limited, due to unresolved issues surrounding the regulation of the expression and secretion systems. In this study, the gene encoding LipA from B. subtilis 168 was expressed in BNA under the control of the P43 and the PAE promoter. The extracellular lipase activity of the resulting strains BNACL and BNAAL was 7.8 U ml-1 and 12.6 U ml-1, respectively. To further enhance the expression of LipA, pHP13L was constructed by inserting the PAE-lip into the shuttle vector pHP13, which produced an extracellular lipase activity of 180.5 U ml-1 of BNA/pHP13L. The strain BNAY8 described in Supplement data which lacks eight extracellular proteins was constructed and the deletion a few of the much weaker secreting proteins had no significant effect on the secretion of LipA. Moreover, the four Sec pathway components, secA-prfB, secDF, secYEG, prsA, were individually overexpressed in BNA. The overexpression of secDF and prsA enhanced the production of LipA by 28% and 49%, respectively. Furthermore, the co-overexpression of secDF with prsA improved the extracellular amount of LipA by 59% over that of BNA/pHP13L, reaching 287.8 U ml-1. It can therefore be said that both regulatory elements and secretion pathway had an impact on the production of secreted LipA. Their optimization and modification is a useful strategy to improve the homologous overproduction of other extracellular proteins in B. subtilis.