A process for the recovery of poly(hydroxyalkanoates) from Pseudomonads Part 1: Solubilization

Abstract

Poly(hydroxyalkanoates) (PHAs) are bacterial storage polyesters, currently receiving much attention because of their potential as biodegradable and renewable plastics. Well known are poly(hydroxybutyrate) and its copolymers with hydroxyvalerate, which have been commercialised under the trademark Biopol. In addition to these rigid materials, the elastomeric medium-chainlength PHAs (mcl-PHAs) from¯uorescent Pseudomonads are now emerging. Here we describe the development of a non-solvent based process for the recovery of mcl-PHAs from the biomass. This ®rst paper addresses a procedure to solubilize the biomass, so that it can be separated from the particulate mcl-PHA. The solubilization procedure, involving heat, protease and detergent, leaves the peptidoglycan intact, which facilitates the separation. The purity of the resulting mcl-PHA exceeds 95%. In a subsequent paper, we utilize the solubilization procedure in a downstream process and we discuss the economics of the corresponding mcl-PHA production.

RECOVERY OF POLYHYDROXYALKANOATES (PHAs) FROM BACTERIAL CELLS USING ENZYMATIC PROCESS

“…65 % w/w of PHA recovered from bacterial cells. However, this result was still lower compared to that obtained by Koning and Witholt (1997) who got a PHA recovery of 95 % w/w. 3 2+3 3+2 2+3+5 2+3+7 2+3+5+7 5 6 5+6 4 4+3 4+2 4+2+3 4+5 4+6 4+5+6 4+6+7 4+5+7 4+5+2+7 5+7 7 4+7 2+3+6 2+3+6+7 4+6+7 4+6+2+7 …”

Start a Research on Biopolymer Polyhydroxyalkanoate (PHA): A Review

“…This combination of enzymes and chemicals were successfully applied to mcl-PHA isolation for fed-batch fermentations of up to 200 L, where the cells were first ruptured by thermal treatment and the resultant debris was exposed to excess protease (alcalase), EDTA and SDS for solubilization. After cross-flow microfiltration, the final mcl-PHA latex had a purity exceeding 95%, demonstrating potential commercial applicability [159,160]. In another study [158], the PHA granules, present in water suspension after enzymatic treatment, were recovered by removing the solubilized non-PHA cell material through ultrafiltration system and purified through continuous diafiltration process.…”

“…While enzyme digestion is a more environmental-friendly approach than solvent extraction, the purity of polymer attained is lower. Biomedical application requires a final purity of 99% or more which is currently not achievable through enzymatic mcl-PHA recovery and a second purification using solvent extraction is necessary [160].…”

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production, biocompatibility, biodegradation, physical properties and applications

“…From an economical point of view, the price of the product ultimately depends on the substrate (mainly carbon source) cost, PHA yield on the substrate and the efficiency of product formulation in the downstream processing (31,107). It is a prerequisite to standardize all the fermentation conditions, and physical and chemical parameters for the successful implementation of commercial PHA production systems (269)(270)(271)(272)(273). PHAs production costs can be reduced by several means, including the use of cheap substrates, such as whey, favored in countries with important dairy industries, or the enhancement of product yield, for example by using recombinant E. coli (7,35,267,274).…”