γ-PGA production through Consolidated Bioprocessing in engineered B. subtilis lab strains

Poly-γ-glutamic acid (γ-PGA) is a nontoxic, biodegradable, highly anionic homo-polyamide formed by multiple repetitions of D-/L- glutamic acid units polymerized by amide linkages between the α-NH2 and γ-COOH groups. The polymer is endowed with several favorable characteristics and has been exploited in a growing number of biotechnological applications. Moreover, ground-breaking γ-PGA applications in the biomedical field, as drug carrier, gene delivery and scaffold for tissue engineering are currently under investigation. The RiVaRIO project is focused on reducing γ-PGA fermentation costs through the exploitation of one of the most abundant biomass resources - rice straw - as unique feedstock in aerobic fermentation. First, a cheap and scalable straw pretreatment was identified that dramatically improves the saccharification efficiency of the lignocellulose matrix. Next, the cellulolytic capabilities of a B. subtilis JH642 were maximized by self-cloning procedures. The efficient growth of B. subtilis on treated straw will be presented. Furthermore, by transferring the cellulolytic modifications in a high-yield γ-PGA producer strain, direct production of γ-PGA from biomass fermentation could be obtained, proving the applicability of Consolidated Bioprocessing concepts to B. subtilis.