Effect of different recovery strategies of P(3HB-co-3HHx) copolymer from Cupriavidus necator recombinant harboring the PHA synthase of Chromobacterium sp. USM2

Five strategies (Experiment A, B, C, D and E) for recovery of PHA were carried out in 10 L bioreactor using cells which contained 68 wt% PHA and 3 mol% 3HHx. NaCl (8 g/L), NaOH (0.1 M) and ethanol (20% v/v) were used in the treatments. Separated treatments of NaCl and NaOH with ethanol (Experiment D) was found as the best strategy with high PHA recovery (95 wt%) and purity (90 wt%). Although, combined treatments (Experiment B) obtained the highest PHA purity (97 wt%) severe degradation of polymer was detected. The molecular weight (Mw) was reduced to almost half (2.8 ×105 Da) compared to polymer extracted using chloroform (4.6 × 105 Da). In addition, pre-treatment using NaCl was found to increase the PHA recovery and purity to 97.7 wt% and 97.5 wt%, respectively. Also, no significant changes in the PHA recovery and purity were observed when lyophilized cell or wet cell was used. Further characterizations of recovered polymers were carried out using GPC, DSC, TGA and tensile machine.

Figure optionsDownload as PowerPoint slideHighlights
► We developed an effective method for large scale recovery of PHA produced by engineered C. necator.
► The method used economical and green chemical/solvent.
► We are able to obtain high PHA recovery (97.7 wt%) and purity (97.5 wt%) with low degradation, The recovered polymer is comparable to chloroform extracted polymer.