Use and reusability of ethyl lactate, as a green solvent, for extraction of poly(3-hydroxybutyrate) from biomass of Paracoccus sp.: Process efficiency, and preliminary evaluation of economic feasibility and environmental impacts

One of the main obstacles for commercialization of poly(3-hydroxybutyrate) (PHB) is the high production cost, which is caused partly by using non-reusable solvents to extract the polymer from biomass of its producer. This, coupling with the toxicity of the conventional solvents, e.g., chloroform and methanol, renders the PHB production process costly and polluting. In this regard, the use of reusable green solvent is a promising approach to reduce both the PHB production cost and the environmental impacts of the process. This study investigated the use of ethyl lactate (EL) as a green solvent to extract PHB from biomass of Paracoccus sp. KKU01. The reusability of EL, as well as economic feasibility and environmental impact of EL-based extraction process, were assessed. Under optimum conditions, the use of EL gave 75.3 ± 0.5 % of PHB recovery, which was comparable to that achieved using chloroform (78.3 ± 5.2 %). The spent EL and ethanol (antisolvent for precipitating PHB from EL) could be reused 10 times with an average PHB recovery of 77.1 ± 0.9 % (w/w) and no obvious loss in the PHB recovery was observed. Preliminary economics assessment showed that reusing EL and ethanol reduced the cost of EL and ethanol procurement by 71 % and 79 %, respectively. Environmental factor (E-factor) and EcoScale evaluations revealed that the EL-based extraction process was more environmentally friendly than the chloroform-based counterpart, due mainly to less generation of wastes. The results demonstrated clearly that EL is an efficient, economically feasible, and environmentally friendly solvent for PHB extraction.