PHB Bio-production from Steam-Exploded Corn Stover by Halomonas hydrothermalis

Abstract

The high production cost of polyhydroxybutyrate (PHB) remains a major barrier to its commercial application. Therefore, it is imperative to develop processes that combine low-cost lignocellulose feedstocks with robust microbial strains. In this study, a fermentation process with an emerging microbial strain was evaluated, possessing the potential to significantly accentuate the kinetics of cell growth and product accumulation. Genome annotation of the strain Halomonas hydrothermalis Slthf2 revealed a complete acyl-CoA-dependent PHB biosynthetic pathway and four full-length putative PhaA homologues, supporting the genetic capacity of H. hydrothermalis Slthf2 for PHB biosynthesis. Response surface methodology based on the Box–Behnken design was used to optimize pH, steam-exploded corn stover (SECS) concentration, and temperature. Based on the optimized conditions, a fed-batch simultaneous saccharification and fermentation (SSF) process with sequential SECS feeding was developed to promote cellulose conversion and PHB accumulation. The optimized process achieved a maximum PHB concentration of 15.1 g/L, corresponding to a PHB content as high as 67.7%. Due to its environmental adaptability and inhibitor tolerance, H. hydrothermalis was identified as an ideal PHB producer in the complex lignocellulosic reaction system containing various inhibitors. This work demonstrates a more sustainable and process-optimized technology for PHB production from lignocellulosic biomass by H. hydrothermalis.