Upstream and Downstream Strategies for Cost Effective Polyhydroxybutyrate (PHB) Production by Bacillus megaterium strain Ti3

Polyhydroxyalkanoates (PHAs) due to their biological origin are gaining attention as nanoparticles for drug delivery systems. However, market penetration of PHAs has been limited by high production costs. The present study attempted economic polyhydroxybutyrate (PHB) production by optimization of media and extraction method using Bacillus megaterium strain Ti3. Response surface methodology-Central composite rotatable design (RSM-CCRD) used to optimize and study the interactions of the independent variables: glucose (1.59–18.41 g/L); KH₂PO₄ (0.08–0.92 g/L) and casein hydrolysate (0.8–9.2 g/L) accounted for maximum PHB Yield (1.2 g/L) by 24 h with glucose (6.11 g/L), KH₂PO₄ (0.75 g/L) and casein hydrolysate (7.5 g/L) amounting to 1.5 folds increase. Cost effectiveness was achieved in terms of reduction of glucose: casein from 2:1 to 1:1. Increase in other fermentation kinetics viz. the PHB productivity (Q _p g _PHB/l/h by 1.7 folds), substrate utilization efficiency (Y _p/s g_PHB/g _S by 2.5 folds) and PHB accumulation (PHB % by 1.12 folds) was observed. Downstream process optimization by one factor approach led to decrease in the extraction time to 15 min (sodium hypochlorite), and 30 min (dispersion) and just 40% hypochlorite concentration, for both the methods. A higher viscosity average molecular weight (Mv) of the recovered PHB of 1258.6±0.75 kDa (optimized hypochlorite) and 1343.3±0.95 kDa (optimized dispersion) was achieved as compared to the 891.2±0.82 kDa (unoptimized hypochlorite) method. NMR analysis of the polymer revealed the strain to be a potent poly (3-hydroxybutyrate) producer. Thus, the present investigation demonstrated an inexpensive model of PHA production in terms of reduction at both upstream and downstream levels without compromising the recovery and quality of biopolymer.