A Review of Bioelectrochemical Strategies for Enhanced Polyhydroxyalkanoate Production

Abstract

The growing demand for sustainable bioplastics has driven research toward more efficient and cost-effective methods of producing polyhydroxyalkanoates (PHAs). Among the emerging strategies, bioelectrochemical technologies have been identified as a promising approach to enhance PHA production by supplying electrons to microorganisms either directly or indirectly. This review provides an overview of recent advancements in bioelectrochemical PHA synthesis, highlighting the advantages of this method, including increased production rates, the ability to utilize a wide range of substrates (including industrial and agricultural waste), and the potential for process integration with existing systems. Various bioelectrochemical systems (BES), electrode materials, and microbial strategies used for PHA biosynthesis are discussed, with a focus on the roles of electrode potentials and microbial electron transfer mechanisms in improving the polymer yield. The integration of BES into PHA production processes has been shown to reduce costs, enhance productivity, and support the use of renewable carbon sources. However, challenges remain, such as optimizing reactor design, scaling up processes, and improving the electron transfer efficiency. This review emphasizes the advancement of bioelectrochemical technologies combined with the use of agro-industrial waste as a carbon source, aiming to maximize the efficiency and sustainability of PHA production for large-scale industrial applications.

Keywords: PHA biosynthesis; bioelectrochemical systems; bioplastics; microbial electrosynthesis; polyhydroxyalkanoates; sustainable production; waste valorization.

Figure 1

Structure and classification of polyhydroxyalkanoates (PHAs), highlighting their structural and compositional diversity. Modified figure from [22].

Figure 2

Evolution of bioelectrochemical system (BES) configurations for value-added product generation. The figure illustrates different configurations utilized in the evolution of bioelectrochemical systems. (A) displays both a microbial fuel cell (MFC) and a microbial electrolysis cell (MEC) configuration. In both, the anodic reaction is the same: the oxidation of organic compounds to CO₂. However, they differ in the cathodic reduction reaction: in an MFC, the cathode typically results in the production of H₂O (generating electricity), while, in an MEC, an external power source is applied to drive the reduction at the cathode, often resulting in H₂ production. (B) presents an MFC and MEC configuration featuring two catalyzed electrodes, highlighting the first instance of electrosynthesis for methane generation from H₂ and CO₂ or CH₄ at the cathode. (C) depicts an electrosynthesis (MES) reactor designed for the production of more complex organic molecules, such as volatile fatty acids (VFA) or PHA, from CO₂. In the latter setup, the significance of microorganisms suspended in the bulk liquid for chain elongation and PHA production is emphasized.