Intracellular polyhydroxyalkanoates recovery by cleaner halogen-free methods towards zero emission in the palm oil mill

In this study, the effect of extraction process, bacterial strain and cell PHA content on halogen-free recovery methods using sodium hydroxide (NaOH) and water as cleaner and more environmental friendly processes were examined for polyhydroxyalkanoates (PHA) recovery. The bacterial strains used were local isolate wild type Comamonas sp. EB172 and recombinant Cupriavidus necator (C. necator), with 30% and 50% of PHA content. It was found that the PHA was efficiently recovered from bacterial cells by the non-halogenated methods. Although the PHA purity obtained by water recovery method was lower than alkaline treatment, it does not have any adverse effect on the polymer molecular weight. The performance of the halogen-free methods depends on the microbial strain which is due to the difference in the thickness of the cell membranes. The intracellular PHA content also affected the effectiveness of the extraction methods for PHA recovery as higher amount of polymer in the cell increased the quantity of PHA recovered. The halogen-free methods using NaOH and water can serve as promising alternatives for conventional industrial halogenated solvent extraction process, since these new methods are environmentally more benign, effective and simple in operation. Finally, the potential of integrating PHA production and halogen free recovery system with the palm oil industry is discussed. It is expected that the proposed integrated system herein provides a more attractive proposition to utilize biomass as renewable resource for the production of value-added bioproducts like PHA, which will make the palm oil industry more sustainable and profitable, and promotes zero-emission at the mill.