(465b) Phasins Employed By Rhodopseudomonas Palustris CGA009 for Bioplastic Production from Lignocellulosic Biomass

Lignocellulosic biomass is considered to be the most economic carbon source in the world, and is thus an ideal candidate for cheaper production of bioplastics. Rhodopseudomonas palustris CGA009 is a very metabolically diverse microbe that can utilize lignin breakdown products to produce bioplastics. Our recent efforts suggest cytoplasmic space is a limiting factor of maximum production of the bioplastic polyhydroxybutyrate (PHB) by R. palustris. Phasins are the dominant proteins surrounding PHB granules that control the size, shape, and abundance of granules. In this study, the Phap1 phasin from Cupriavidus necator H16 was expressed in R. palustris with the aim of overproducing PHB from lignocellulosic sources. Phap1 leads to smaller and more abundant PHB granules in C. necator, and it was hypothesized that expression of this phasin would increase overall titers from R. palustris. Transmission electron microscopy revealed that indeed Phap1 expression yielded smaller and more abundant granules in both aerobic and anaerobic conditions compared to the wild type strain. Expression of Phap1 yielded PHB production from R. palustris aerobically (0.7 g/L), which does not occur in the wild type strain. Although the Phap1 expression modified the granules in anaerobic conditions, the PHB titer was not as high compared to the wild type strain. This suggests that phasin performance may be optimal under certain conditions since C. necator is typically an aerobic microbe. Our ongoing efforts are aimed at quantifying changes in gene expression to develop a more holistic analysis of R. palustris’ PHB production framework, including Phap1 as well as native phasins employed by R. palustris that have never been reported.