Rewiring glycerol metabolism for enhanced production of poly-?-glutamic acid in Bacillus licheniformis.

ABSTRACT: Background:Poly-?-glutamic acid (?-PGA) is a natural polymer with great potential applications in areas of agriculture, industry, and pharmaceutical. The biodiesel-derived glycerol can be used as an attractive feedstock for ?-PGA production due to its availability and low price; however, insufficient production of ?-PGA from glycerol is limitation. Results:The metabolic pathway of Bacillus licheniformis WX-02 was rewired to improve the efficiency of glycerol assimilation and the supply of NADPH for ?-PGA synthesis. GlpK, GlpX, Zwf, and Tkt1 were found to be the key enzymes for ?-PGA synthesis using glycerol as a feedstock. Through combinational expression of these key enzymes, the ?-PGA titer increased to 19.20?±?1.57 g/L, which was 1.50-fold of that of the wild-type strain. Then, we studied the flux distributions, gene expression, and intracellular metabolites in WX-02 and the recombinant strain BC4 (over-expression of the above quadruple enzymes). Our results indicated that over-expression of the quadruple enzymes redistributed metabolic flux to ?-PGA synthesis. Furthermore, using crude glycerol as carbon source, the BC4 strain showed a high productivity of 0.38 g/L/h, and produced 18.41 g/L ?-PGA, with a high yield of 0.46 g ?-PGA/g glycerol. Conclusions:The approach to rewiring of metabolic pathways enables B. licheniformis to efficiently synthesize ?-PGA from glycerol. The ?-PGA productivity reported in this work is the highest obtained in glutamate-free medium. The present study demonstrates that the recombinant B. licheniformis strain shows significant potential to produce valuable compounds from crude glycerol.

SUBMITTER: Zhan Y 

PROVIDER: S-EPMC6225680 | biostudies-other | 2018

REPOSITORIES: biostudies-other