Biodepolymerisations of intracellular and extracellular polyhydroxyalkanoates: Methodological approaches and current update on biotechnological applications

Polyhydroxyalkanoates (PHAs) are microbial polyesters synthesised as intracellular carbon and energy storage compounds, with significant potential as sustainable and biodegradable alternatives to petroleum-based plastics. Their degradation, or depolymerisation, occurs through both intracellular and extracellular mechanisms, each offering unique methodological challenges and opportunities. This review provides a comprehensive overview of current methodological approaches for studying PHA depolymerisation via enzymatic hydrolysis, encompassing in vivo and in vitro intracellular depolymerisation, as well as environmental, in vivo, and in vitro extracellular depolymerisation processes. Furthermore, recent advances in the biotechnological applications of PHA depolymerisation products, especially enantiomerically pure (R)-3-hydroxyalkanoates, are discussed. These monomers are increasingly exploited in the production of versatile chiral building blocks with diverse applications, ranging from pharmaceuticals and food additives to biodegradable plastics and plant protection. This review aims to consolidate the current knowledge base and highlight emerging methodological approaches in studying PHA depolymerisation and applications of its depolymerised products.