An efficient and reusable N,N-dimethylacetamide/LiCl solvent system for the extraction of high-purity polyhydroxybutyrate from bacterial biomass

Multiple methods have been developed for the extraction of the bioplastic polyhydroxybutyrate (PHB) from bacteria. Many of these approaches suffer from low efficiency, are toxic, non-reusable, complex, and costly, which prompts the development of alternative processes. The N,N-dimethylacetamide/LiCl (DMAc/LiCl) solvent system is a widely employed, reusable, and simple method for the solubilization of cellulose and other biological macromolecules. Since bacteria are mostly constituted of polysaccharides, proteins, and other polymers, it may be possible to employ DMAc/LiCl to dissolve them and extract bioplastics. Here, the DMAc/LiCl system was adapted for the breakage of PHB-producing Cupriavidus necator cells combined with the extraction of the poly-ester. After screening for optimized conditions, the extraction was carried out by incubating 200 mg of dry biomass at 110 celcius for three hours in DMAc/LiCl. With these parameters, the recovery rate was 95.3% with an excellent PHB purity of 99.0%. Furthermore, the solvent could be reused five times with a minimal loss of ef-ficiency. Extracted PHB characterization indicated that it exhibited physicochemical properties comparable to commercial PHB including its molecular weight, thermal stability, and crystallinity. Thus, the DMAc/LiCl-based extraction of high-purity PHB has the potential to become a widespread method because of its efficiency, recyclability, and convenience.