(182e) Bioconversion of Lignocellulose Biomass into Biodegradable Plastics

Escalating concerns about CO 2 emission from fossil fuels utilization and environmental pollution from fossil-derived plastic waste call for the sustainable production and utilization of renewable biodegradable plastic materials. Polyhydroxyalkanoates (PHA) are a type of biodegradable and biocompatible thermoplastics with thermal and mechanical properties comparable to conventional plastics; therefore, they are promising materials for avoiding environmental pollution and for sustainability purposes. PHA can be synthesized by various microorganisms under stress conditions. However, currently biosynthesized PHA are relatively expensive primarily due to high substrate cost. Therefore, biomanufacturing PHA from cheap renewable raw materials is garnering increased attention. Lignocellulose hydrolysates are cheaper organic feedstocks for microbial bioprocesses, but there are usually certain compounds that inhibit enzyme activities and cell growth. Elucidating bottlenecks of cellular metabolism when using lignocellulose hydrolysates as the raw material for biomanufacturing bioproducts remains challenging. In this study, we have first demonstrated successful biomanufacturing medium-chain-length (mcl) PHA by Pseudomonas putida KT2440 derivative strains from three types of lignocellulosic biomass hydrolysates. The yields and compositions of mcl-PHA are comparable to that directly synthesized from pure glucose, with 3-hydroxydecanoic acid being the dominant building-block followed by 3-hydroxyoctanoic acid. We also studied the impact of different stress conditions, such as nitrogen limitation, on the yield and composition of PHA. Through performing a systematic analysis of the metabolic fluxes for the PHA-producing P. putida cells, we have elucidated competing pathways and potential metabolic bottlenecks within mcl-PHA- producing cells. These findings provide insights into strategies to further enhance biomanufacturing of mcl-PHA from lignocellulosic biomass hydrolysates.