Starch based polyhydroxybutyrate production in engineered Escherichia coli

Every year, the amount of chemosynthetic plastic accumulating in the environment is increasing, and significant time is required for decomposition. Bio-based, biodegradable plastic is a promising alternative, but its production is not yet a cost effective process. Decreasing the production cost of polyhydroxyalkanoate by utilizing renewable carbon sources for biosynthesis is an important aspect of commercializing this biodegradable polymer. An Escherichia coli strain that expresses a functional amylase and accumulate polyhydroxybutyrate (PHB), was constructed using different plasmids containing the amylase gene of Panibacillus sp. and PHB synthesis genes from Ralstonia eutropha. This engineered strain can utilize starch as the sole carbon source. The maximum PHB production (1.24 g/L) was obtained with 2 % (w/v) starch in M9 media containing 0.15 % (w/v) yeast extract and 10 mM glycine betaine. The engineered E. coli SKB99 strain can accumulate intracellular PHB up to 57.4 % of cell dry mass.