Enzymatic Transformation of Bacterial Polyhydroxyalkanoates into Repolymerizable Oligomers Directed towards Chemical Recycling

• Published in: Macromolecular bioscience Vol. 5; no. 7; pp. 644 - 652
• Main Authors: Kaihara, Sachiko, Osanai, Yasushi, Nishikawa, Kimihito, Toshima, Kazunobu, Doi, Yoshiharu, Matsumura, Shuichi
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 14.07.2005; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Alcaligenes faecalis; Alcaligenes faecalis - enzymology; Applied sciences; Bacteria; Biocompatible Materials - chemical synthesis; Biocompatible Materials - metabolism; Biodegradation, Environmental; Candida antarctica; Carboxylic Ester Hydrolases - chemistry; cyclic oligomers; degradation; enzymes; Enzymes, Immobilized - chemistry; Exact sciences and technology; Fungal Proteins; Lipase - chemistry; poly(3-hydroxyalkanoate)s; Polyesters - chemical synthesis; Polyesters - metabolism; Polymer industry, paints, wood; Polymers - chemical synthesis; Polymers - metabolism; Pseudomonas stutzeri; Pseudomonas stutzeri - enzymology; recycling; Technology of polymers; Waste treatment; Ring opening polymerization; Valerate(hydroxy) copolymer; Triacylglycerol lipase; Butyrate(hydroxy) copolymer; Enzymatic catalysis; Esterases; Oligomer; Solution polymerization; Depolymerization; Caprolactone copolymer; Recycling; Chemical reactivity; Lactone copolymer; Enzyme; Ester polymer; Butyrate(hydroxy)polymer; Experimental study; Carboxylic ester hydrolases; Ester copolymer; Microbial origin; Propiolactone copolymer; Cyclic polymer; Preparation; Enzymatic digestion; Hydrolases; Prepolymer; Ring opening copolymerization; Immobilized enzyme
• ISSN: 1616-5187; 1616-5195
• DOI: 10.1002/mabi.200500030

The enzymatic transformation into an oligomer was carried out with the objective of developing the chemical recycling of bacterial polyesters. Poly(R‐3‐hydroxyalkanoate)s (PHAs), such as poly[(R‐3‐hydroxybutyrate)‐co‐12%(R‐3‐hydroxyhexanoate)] and poly[(R‐3‐hydroxybutyrate)‐co‐12%(R‐3‐hydroxyvalerate)], were degraded by granulated Candida antarctica lipase B immobilized on hydrophilic silica (lipase GCA) in a diluted organic solvent at 70 °C. The degradation products were cyclic oligomers having a molecular weight of a few hundreds. The obtained cyclic oligomer was readily repolymerized by the same lipase (lipase GCA) to produce the corresponding polyester in a concentrated solution. The cyclic oligomer was copolymerized with ε‐caprolactone using lipase to produce the corresponding terpolymers having an $\overline M _{\rm w}$ of 21 000. This is the first example of the enzymatic chemical recycling of bacterial PHAs using lipase. Poly(R‐3‐hydroxybutyrate) [P(3HB)] was also degraded into the linear‐type R‐3HB monomer to trimer by P(3HB)‐depolymerase (PHBDP) in phosphate buffer at 37 °C. The degradation using PHBDP required a longer reaction time compared with the lipase‐catalyzed degradation in organic solvent. The monomer composition of the oligomer depended on the origin of the PHBDP. The R‐3HB monomer was predominately produced by PHBDP from Pseudomonas stutzeri, while the R‐3HB dimer was produced by PHBDP from Alcaligenes faecalis T1. Repolymerization of these oligomers by lipase in concentrated organic solvent produced a relatively low‐molecular‐weight P(3HB) (e.g., $\overline M _{\rm w}$ = 2 000). Degradation of P(3HB) by lipase in organic solvent into repolymerizable cyclic oligomer and degradation of P(3HB) by PHBDP in buffer into hydroxy acid type R‐3HB dimer.