Sustainable Bioconversion of Cassava Waste to Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Halogeometricum borinquense Strain E3

Abstract

The production of sago starch from cassava at an industrial scale in Salem, Tamil Nadu, India results in discharge of starch/carbon-rich fibrous waste and effluents, contributing to a major environmental problem. The present study aimed at exploring the potential of an extremely halophilic archaeon, Halogeometricum borinquense strain E3 to utilize starch and cassava waste (CW) as carbon substrate and synthesis of polyhydroxyalkanoates (PHAs). The culture E3 was able to grow and utilize both starch and CW with maximum PHA concentration of 4.6 g L−1 and 1.52 g L−1, respectively. When grown in starch, the cells of the strain E3 appeared bright orange due to produced carotenoids, whereas, when grown in CW the culture cells appeared light brown due to masking of the pigment by the impurities from CW hydrolysate. The polymer obtained from starch and CW hydrolysate was characterized using UV–Visible spectrophotometry, differential scanning calorimetry, fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and was reported to be a co-polymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] comprising of 13.11% and 19.65% 3HV units, respectively. The present investigation is supportive of our previous studies which indicated Hgm. borinquense strain E3 as an attractive candidate for production of co-polymer of P(3HB-co-3HV) when fed with commercial substrate such as glucose and agro-industrial waste such as sugarcane bagasse.