Efficient Lactic Acid Production from Dilute Acid Pretreated Lignocellulosic Biomass by a Synthetic Consortia of Engineered Pseudomonas Putida and Bacillus Coagulans

Background Lignocellulosic biomass is an attractive and sustainable alternative to petroleum-based feedstock for the production a range of biochemicals, and a pretreatment is generally regarded to be indispensable for its bio-refinery. Nevertheless, various inhibitors that severely hindered the growth and fermentation of microorganisms were produced inevitably during the pretreatment of lignocellulose. Presently, a single microorganism that can tolerate toxic mixtures of pretreatment hydrolysate while effectively transforming sugar components into valuable compound is less well reported. Alternatively, microbial co-culture provides a simpler and more efficacious way to realize this goal via distributing metabolic tasks among proper strains. Results In this study, a novel synthetic microbial consortia, which is composed of a responsible for detoxification bacterium engineered Pseudomonas putida KT2440 and a lactic acid production specialist Bacillus coagulans NL01, was developed to directly produce lactic acid from high-toxic lignocellulosic hydrolysate. The engineered P. putida with deletion of sugar metabolism pathway was suggested to be unable to consume the major fermentable sugars of lignocellulosic hydrolysate, but can rapidly remove inhibitors in hydrolysate. With detoxification using engineered P. putida for 24 h, the pretreated hydrolysate was fermented into 35.8 g/L of lactic acid by B. coagulans with a yield of 90%. The fermentation performance of microbial co-culture was significantly improved than that single culture of B. coagulans without lactic acid production. Conclusions The microbial coculture system constructed by this study demonstrated strong potential of the process for biosynthesis of valuable product from lignocellulosic hydrolysate containing high concentration of complex inhibitors by specifically recruited consortia of robust microorganisms with desirable characteristics and also provided a feasible and attractive method for bioconversion of lignocellulosic biomass to other value-added biochemicals.