Xylose Utilization for Polyhydroxyalkanoate Biosynthesis

The sustainable production of biochemicals is primarily driven by the costs associated with the specific biosynthetic process. To maximize the economics of any bio-based synthetic process, efforts are focused on the utilization of low-value, high-volume substrates to produce environmentally-benign, high-value products with a range of applications. One such substrate is xylose. Xylose is the main sugar associated with hemicellulose and is the second most abundant sugar in nature representing approximately 20-30% of the sugars present in terrestrial plant biomass. Polyhydroxyalkanoates (PHA) are bacterial polyesters that possess properties analogous to those demonstrated by a range of widely-utilized petroleum-based polymers with the added advantages of being biorenewable, biodegradable, and biocompatible. As such, xylose is currently recognized and evaluated as a potentially beneficial feedstock for the synthesis of many different products including PHA biopolymers. This chapter focuses on the utilization of xylose for PHA biosynthesis including membrane transport, and its integration into the central metabolic pathways associated with PHA production, its conversion to levulinic acid (a valuable co-substrate for copolymer synthesis) as well as identifying the different bacterial strains capable of PHA synthesis from xylose and the types of PHA produced.