Screening and application of inducible promoters in Ruminiclostridium papyrosolvens.

Ruminiclostridium papyrosolvens is a promising candidate for producing renewable green chemicals from cellulose due to its cellulolytic and ethanologenic capabilities. It is of significance to screen effective, and convenient-to-use inducible promoters that can be used for regulating the gene expression in Ruminiclostridium papyrosolvens. We characterized two endogenous inducible promoters and investigated another two exogenous ones on the adaptability in R. papyrosolvens. Both of the endogenous xylan-inducible promoter Pxyl and exogenous lactose-inducible promoter Plac are found of high specificity and stringency. Pxyl has short time to be induced while Plac has the low concentration of inducer. With these findings, a mazF-based counterselection system has been constructed for promoting the efficiency of mutant screening via plasmid curing. The inducible gene expression systems provided novel tools for enhancing the capability of genetic manipulation in engineering R. papyrosolvens.