Polyhydroxybutyrate (PHB) Biosynthesis by an Engineered <i>Yarrowia Lipolytica</i> Using Co-Substrate Strategy

Abstract

High production cost is one of the major factors that limit the market growth of polyhydroxyalkanoates (PHAs) as a biopolymer. Improving PHA synthesis performance and utilizing low grade feedstock are two logical strategies for reducing the cost. As an oleaginous yeast, Y. lipolytica has a high carbon flux through acetyl-CoA (main PHB precursor) which makes it a desired cell factory for PHB biosynthesis. Two different metabolic pathways introduced into Y. lipolytica PO1f in this study for enhancing PHB biosynthesis, along with glucose and acetate as co-substrates. Results showed that NBC pathway led to more than 11% PHB accumulation, while there was non-detectable PHB accumulations using ABC pathway. Further modifications were done using peroxisomal compartmentalization and gene-dose overexpression. Final strain showed up to 41% PHB of CDW with a growth rate of 0.227 h-1. Low growth rate was observed using acetate or glucose as sole carbon and energy source. The co-substrate strategy showed compensatory effect on overcoming inhibitory and toxic effects of both substrates at high concentrations. Cultivating the engineered strain in optimal co-substrate condition predicted by RSM led to 83.4 g/L biomass concentration and 31.7 g/L PHB.