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Minimum Run Resolution IV screening design was employed to study important process factors to maximize Dry cell weight (DCW) and Polyhydroxyalkanoate (PHA) production by Massilia spp. From screening design, it was observed that maltose, NH4HPO4, Na2HPO4 and K2HPO4 were found to be significantly affecting DCW and PHA production. A three-level-four-factor central composite design (CCD) was employed in combination with response surface methodology (RSM) to optimize the concentration of screened factors. The statistical analysis of results showed that maltose and NH4HPO4 had a positive effect whereas Na2HPO4, K2HPO4 had a negative effect on DCW and PHA production. By using RSM, optimum concentration of significant factors was found to be as follows: maltose: 30.0 g/l, NH4HPO4: 3.0 g/l, Na2HPO4: 3.0 g/l, K2HPO4: 3.0 g/l. Verification of the predicted value resulted into a yield of 25.5 g/l of DCW and 6 g/l of PHA.

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Cane molasses is an inexpensive, sustainable by-product of the sugar industry, which supports the growth of microorganisms as it contains several growth factors. Response Surface Methodology (RSM) employing central composite design (CCD) was applied to enhance PHA production by Massilia sp at shake flask level by using molasses as a carbon source. Isolate produced maximum DCW (54.0 g/l) and PHA (3.0 g/l) when medium was optimized with the help of CCD. Optimized concentration of medium components to maximize PHA production was found to be as follows: molasses: 100.0 g/l, NH4HPO4 : 1.67g/l, Na2HPO4 : 5.86g/l, K2HPO4 : 5.74g/l, MgSO4 : 0.25g/l, trace element solution: 0.1ml/l. The point optimization method reported a small difference of 0.02g/l, indicating the validity of mathematical models developed after applying CCD.