Sustainable Bioelectrosynthesis of the Bioplastic Polyhydroxybutyrate: Overcoming Substrate Requirement for NADH Regeneration

• Published in: ACS sustainable chemistry & engineering Vol. 6; no. 4; pp. 4909 - 4915
• Main Authors: Alkotaini, Bassam, Abdellaoui, Sofiene, Hasan, Kamrul, Grattieri, Matteo, Quah, Timothy, Cai, Rong, Yuan, Mengwei, Minteer, Shelley D
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02.04.2018
• Subjects: Polyhydroxybutyrate; Sustainable bioplastic; Bioelectrosynthesis; in vitro; NADH regeneration
• ISSN: 2168-0485; 2168-0485
• DOI: 10.1021/acssuschemeng.7b04392

One of the main limitations to achieve sustainable synthesis of polyhydroxybutyrate (PHB) is the cost of NADH regeneration, as it requires a side enzymatic reaction usually including a NAD-dependent dehydrogenase enzyme with its substrate or other photo- and electrochemical approaches that create unwanted byproducts and the enzymatically inactive dimer NAD2. Herein, a bioelectrocatalytic method combining both enzymatic and electrochemical approaches was used to regenerate enzymatically active NADH. The method employed a modified glassy carbon electrode that possesses both NADH regeneration and acetoacetyl-CoA (AcAcCoA) reduction features. The modified electrode exhibited an apparent Michaelis constant (K M) value of 814 ± 11 μM and a maximum current density (j max) of 27.9 ± 1.3 μA cm–2 for NAD+ reduction and a K M value of 47 ± 2 μM and j max of 0.97 ± 0.03 μA cm–2 for AcAcCoA reduction. The modified electrode was subsequently employed in the bioelectrosynthesis of the bioplastic PHB and yielded 1.6 mg in a 5 mL reaction mixture, indicating that the NADH was regenerated at least 8 times during the 16 h reaction.