Agro-industrial byproducts as alternate cost-effective medium components for production of poly-β-hydroxybutyrate

Abstract

Polyhydroxybutyrates (PHBs), biodegradable plastics, having properties similar to conventional plastics, exhibit a high potential for replacing petrochemical-based non-degradable plastics. But a major obstacle in their large-scale commercial production is high production cost, one of the key factors responsible for which is the expensive carbon sources that are currently being used in their manufacturing process. The present work was aimed to study PHB production using cost-effective substrates as carbon sources in the production medium. Inexpensive agro-industrial byproducts (molasses, cheese whey, wheat bran and banana peel, used in different concentrations) were explored for their potential to substitute the conventional costly substrates. Compared to glucose, all the four alternate carbon sources showed an enhancement in PHB production. The mean percent increase in PHB production was in the range of 3.81% to 7.23%. However, some of the bacterial isolates showed an enhancement as high as 23.32% and 19.65%. Highest mean PHB yield was observed in molasses (135.18 mg/mL), followed by cheese-whey (133.79 mg/mL), banana peel, and least in wheat bran based production medium. On dry weight basis, PHB accumulation in cells was observed to be 64.32% and 64.29% of the total dry cell weight with molasses and cheese whey, respectively, as carbon sources. FTIR spectra of extracted PHB were found to be comparable to the spectra of standard PHB, thus, confirming the chemical nature of the extracted polymer.