Investigation of effective factors on optimization of biopolymer production of polyhydroxybutyrate-co-valerate (PHBV) by Plackett–Burman method and optimization of productivity by high cell density technique

Polyhydroxy alkanoates are biodegradable and biocompatible polymers produced by a wide range of bacterial strains. In the present study, the natural strain of Bacillus cereus producing polyhydroxybutyrate-co-valerate (PHBV) copolymer with high productivity isolated from starch effluent was used. In order to produce, starch effluent was studied as a cheap and expensive culture medium. Then, by examining the effective factors, the optimal composition of the culture medium was evaluated and in order to achieve higher productivity, the culture method with high cell density was evaluated. The results showed that the mean maximum production of PHBV using the platelet-Berman test design method (culture medium related factors) was about 3.07 g / l (59.5% of cell dry weight). Subsequently, by optimizing culture with high cell density, the production rate increased to 4.45 g / l (more than 72% of dry cell weight). Therefore, it can be concluded that the high-density cell culture method has a significant effect on increasing the productivity of PHBV production by B. cereus. Due to the use of cheap culture medium and the cost of wastewater, the importance of these results is twofold and shows the potential for production on an industrial scale.