Second-generation polyhydroxyalkanoates production as a strategy to improve performance of first-generation bioethanol biorefineries

Polyhydroxyalkanoates (PHAs) are biopolymers produced by microorganisms that use renewable feedstocks as substrate. Since their discovery, different processes have been designed and implemented for their application in single-use plastics, pharmaceutical, and agricultural fields. To achieve sustainable production of this bioplastic, the concept of biorefineries should be considered as an alternative, where first-generation (1G) bioethanol is produced, and the residue of this process is used as the substrate for second-generation (2G) PHA production. Such integrated biorefinery model fits in the principles of circular economy by transforming lignocellulosic residues into higher-value molecules, while enhancing the economic and environmental performance of traditional bioethanol production platforms. Therefore, this review aims to describe the current technologies in biomass pretreatment, PHAs synthesis, and process integration in 1G/2G biorefineries, summarizing their drawbacks and advantages. This fact suggests that PHA production in 1G/2G biorefineries platforms provides a solution for both waste management and large-scale biomolecules production.