Biosynthesis of polyhydroxyalkanoates from sugarcane molasses by recombinant Ralstonia eutropha strains

Abstract

Sugarcane molasses was examined for the production of poly(3-hydroxybutyrate) [P(3HB)] and poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] in recombinant Ralstonia eutropha strains expressing Mannheimia succiniciproducens sacC gene encoding β-fructofuranosidase, which can hydrolyze sucrose into glucose and fructose in the culture medium. When crude sugarcane molasses was added to the culture medium to support 20 g/L of sucrose in flask cultivation, the growth of R. eutropha NCIMB11599 expressing the sacC gene was significantly inhibited, which resulted in OD600 of 1.2 with P(3HB) content of 0.1wt%. The inhibition of cell growth due to the usage of the crude sugarcane molasses was relieved by pretreatment of sugarcane molasses with activated charcoal. Sugarcane molasses pretreated with activated charcoal could support the growth of R. eutropha NCIMB11599 expressing the sacC gene to OD600 of 87.2 with P(3HB) content of 82.5 wt% in batch fermentation when it was added to culture medium to support 20 g/L of sucrose. Also, R. eutropha 437–540 expressing Escherichia coli ldhA gene encoding lactate dehydrogenase along with the sacC gene produced P(3HB-co-6.2 mol%LA) with 29.1 wt% polymer content from sugarcane molasses in batch fermentation. © 2021, The Korean Institute of Chemical Engineers.