Starch based polyhydroxybutyrate production in engineered Escherichia coli

Abstract

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.

Characterization of poly-3-hydroxybutyrate (PHB) produced from Ralstonia eutropha using an alkali-pretreated biomass feedstock

“…Good bacterial growth on the PS hydrolysate indicated the absence or inactivity of any inhibitors known to occur in lignocellulosic biomass. On the other hand, for complete utilization of PS hydrolysate, it is necessary to detoxify the hydrolysate to remove fermentation inhibitors such as phenolic compounds, furfural, and hydroxymethyl furfural, which may be present in small amounts [13,17,32]. Feeding of PS hydrolysates yielded DCW and PHB productivity that were similar to those with equivalent mixture of laboratory-grade sugars ( Table 2).…”

“…The mobile phase was 10 mM H 2 SO 4 at the flow rate of 0.5 mL/min and column oven temperature was controlled at 55 • C. Fourier-transform infrared (FTIR) spectroscopy (Agilent, Cary 630; USA) of untreated and alkali-pretreated PS was conducted in the mid-infrared region by averaging 32 scans in the range 400-4000 cm −1 at resolution 4 cm −1 to detect changes in the functional groups. Scanning electron microscopy (SEM) images of the particles coated with platinum were obtained using a JEOL JSM-6360A microscope (Tokyo, Japan) at operating voltage 20 kV using the procedure reported earlier [13]. Samples of the untreated and alkali-pretreated PS biomass were analyzed by X-ray diffraction (XRD) in D2 Phaser table-top model, Bruker, Germany operating at 30 kV, 10 mA; the radiation was Cu (1.54Å) and grade range between 12 • and 45 • with a step size of 0.02 • .…”

“…Lignocellulosic biomass has been considered as an ideal feedstock for bioplastics (PHB) production being most abundant and renewable biomass on the earth [12]. However, formation of soluble sugars from cellulose of agricultural residues relies on the sequential/coordinated action of cellulases, primarily endoglucanase, exoglucanase, and cellobiase [12,13]. Moreover selection of microbial strains that utilize a cheaper and more abundant lignocellulosic biomass as a carbon source as well as selection of more efficient fermentation strategies may make PHB production more feasible and cost effective [7,10].…”

Enhanced production of poly(3-hydroxybutyrate) in recombinant Escherichia coli and EDTA–microwave-assisted cell lysis for polymer recovery

“…Genetically engineered E. coli , with some deletions such as mtgA and mreB were observed to be improving PHB production via enhanced inclusion body accumulation and cell enlargement (Jiang et al 2015; Kadoya et al 2015). Integration of amylase gene into recombinant E. coli is a strategy to make use of starch as the sole carbon source for PHB production (Bhatia et al 2015). Application of these techniques in the recombinant strain developed in this study may improve it’s the industrial applicability.…”

Integrated systems for biopolymers and bioenergy production from organic waste and by-products: a review of microbial processes

“…However, to overcome the high costs of the hydrolysis of starch into glucose by a two-step process (liquefaction and saccharification), making this feedstock less economically viable, Bhatia et al [72] constructed the recombinant E. coli strain SKB99 harboring plasmids containing genes for starch hydrolysis (from Paenibacillus sp.) and PHB synthesis (from R. eutropha ).…”