Kinetics and model building for recovery of polyhydroxyalkanoate (PHA) from Halomonas campisalis

Moderately haloalkaliphilic Halomonas campisallis MCM B-1027 isolated from the alkaline lake of Lonar, India was found to produce a biodegradable polymer, polyhydroxyalkanoate (PHA). Scale up production of PHA from H. campisalis MCM B-1027 was carried out in 120 L stainless steel (SS) fermenter using 85 L production medium with a yield of 51.56% PHA on dry cell weight basis. The recovery of PHA was studied by several methods such as solvent extraction of the polymer, chemical digestion of the non-PHA biomass and mechanical disruption of the cells. Highest rate of PHA recovery obtained was 63 mg/h with solvent extraction using rotary film evaporator. Further optimization of extraction of PHA from dry cells in chloroform using 10 L rotavapor was carried out. L9 orthogonal array was chosen to study the influence of time, rotation and temperature at three levels along with their interactive effects on extraction process. Maximum PHA recovery of 84.47% was obtained at 25 rpm, 60 °C, within 3 h. Time factor had highest 84.11% contribution in the extraction process. This study is the first report on model for batch extraction of PHA and its validation based on second-order mechanism developed to predict the saturation capacity of the solvent, initial rate of extraction at different temperatures and activation energy of the process.

► Optimization of PHA recovery carried out using Taguchi orthogonal array L9.
► Contribution of individual factor and their interactive effect on PHA recovery.
► First report on validation of model for batch extraction of PHA.
► Prediction of the saturation capacity of solvent and initial rate of extraction.
► First report on activation energy required for PHA extraction.