Homologous Overexpression of Genes in Cordyceps militaris Improves the Production of Polysaccharide

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Abstract

Abstract Background Cordyceps polysaccharides have been used around the globe for its bioactivity for millennia. However, the study and medicinal of Cordyceps militaris polysaccharides has been hampered by the low in natural abundances. Recently, the genetic engineered C. militaris developed for production of exopolysaccharides (EPS) had received extensive attention. Results In this study, based on the biosynthetic pathway and metabolization mechanism of exopolysaccharides, the crucial biosynthetic genes of Cordyceps polysaccharides were introduced by Agrobacterium transformation to provide a high flux of EPS. 21 mutants of C. militaris were identified through antibiotic screening and DNA sequencing. The maximum yield of EPS produced by mutant CM- pgm -H was 4.63 ± 0.23 g/L, while the yield of wild-type strain was 3.43 ± 0.26 g/L. And the data obtained in the present study indicated that the yield of EPS produced by the engineered strain treated with co-overexpression of phosphoglucomutase and UDP-glucose 6-dehydrogenase genes achieved 6.11 ± 0.21 g/L, which was increased by 78.13% compared with the wild-type strain. Conclusions CM- pgm -H obtained the highest EPS content than that of mutants glucokinase, UDP-glucose pyrophosphorylase, UDP-glucose 6-dehydrogenase. It indicated that the content of protein phosphoglucomutase was the most critical influencing factor on the CP production in C.militaris. Furthermore, the EPS production of CM- ugdh - pgm -M was significantly improved 1.78-fold by co-overexpression. It anticipated that our engineering strategies will play an important role in the development of C. militaris for sustainable production of Cordyceps polysaccharides.