Optimisation of the production of environmental friendly bioplastic, polyhydroxyalkanoate (PHA) from glycerol by Burkholderia cepacia BPT1213 in shake flask cultures

Abstract

Polyhydroxyalkanoates (PHAS) are touted as the environmental friendly alternative to recalcitrant petrochemical derived plastics. PHA is produced by bacteria through fermentation of sugar, lipids and other carbon sources. A bacterial strain previously isolated and identified as Burkholderia cepacia_BPT1213 was able to consume glycerol to yield high cell biomass with PHA content. The strain was grown in 50 mL mineral salt media (MSM) supplemented with 2% of glycerol in 250 mL shake flask at different growth conditions. Response surface methodology (RSM) analysis was carried out to determine the influence of different fermentation temperatures (28-37°C), initial pH of the culture media (5-9) and inoculum size (4-10%), using a combination and level of factors. The responses, cell dry weight (CDW) and PHA content (% CDW), were analysed for interactive effects between the selected variables. Later, the optimum point of each factor was predicted by using Design Expert version 7.1.2 (Stat-Ease Inc., Minneapolis, USA) software. The suggested optimum points for the best CDW and PHA content was found to be 37°C, initial pH 9 and 4% of inoculum size; predicted to give 2.81 g/L of CWD with 76% PHA content. Experimental verification gave a yield of 3.94 g/L CDW and 78% PHA content.