Polyhydroxyalkanoate production from marine bacteria optimization strategies and application studies

Abstract

Polyhydroxyalkanoates are defined as a type of natural biodegradable polymers that are newlinesynthesized by many microorganisms. In this study, PHA producing bacteria were isolated from marine water samples collected from Calicut region of Kerala through serial dilution followed by Nile blue and Sudan black staining. 3 PHA producing isolates designated as SG1, TS1, SG2 were further subjected to quantitative screening for PHA production using M9 minimal media. After the quantitative screening, 2 strains namely isolate SG1 (0.67 g/L) and isolate TS1(0.52 g/L) that produced highest PHA yield were selected for further studies. The isolates SG1 and TS1 were identified to be Bacillus subtilis and Bacillus cereus respectively through biochemical test and 16S rRNA sequencing. Initially M9 minimal media was used for the PHA production from bacteria. Screening for enhancing PHA production using various PHA production media employing Bacillus subtilis SG1 and Bacillus cereus TS1 were carried out prior to statistical optimization. The effect of bioprocess parameters like temperature, pH, incubation period, inoculum level, NaCl concentration, carbon and nitrogen source on PHA production was assessed using one factor at a time (OFAT) approach. The interaction effects of most influential parameters (NaCl concentration, carbon source, nitrogen source and incubation period) on PHA production was evaluated using central composite design (CCD) based two level, two-factor interaction (2FI), factorial model to optimize PHA production. Using the Analysis of Variance technique, the significance of the model was determined. Under optimized condition an enhanced PHA yield of 1.52 g/L and 1.13 g/L respectively were obtained from Bacillus subtilis SG1 and Bacillus cereus TS1. And these results suggested 2.26 and 2.51fold increase in PHA production after optimized conditions from Bacillus subtilis SG1 and Bacillus cereus TS1. Effect of a cost effective and abundantly available carbon source (flower waste) supplementation on enhancing.