Deregulation of cellulose synthesis by site-directed mutagenesis of cellulose synthase leads to heightened bacterial cellulose production

Abstract

Background Bacterial cellulose produced via fermentation is a promising alternative to plant-derived cellulose with the potential to provide a sustainable source of cellulose with a significantly lower environmental footprint than unsustainable sources of cellulose such as wood pulp. Optimisation of the production system is needed to raise productivity and achieve commercial viability. The organism used is a key component of this system and a key target for optimisation by strain development procedures. Wild strains of cellulose-producing bacteria regulate their cellulose synthesis in response to the environment. Deregulation of cellulose synthesis is necessary to achieve higher yields. A key regulatory target for strain engineering is the post-translational deregulation of cellulose synthase that is regulated by cyclic-di-GMP. It has been demonstrated in vitro that mutating the N-terminal arginine residue of the RXXXR motif creates a constitutively active cellulose synthase, but its in vivo effect has not yet been explored.Results In this study, we investigate the effect of mutating the N-terminal arginine residue of the RXXXR motif in vivo with a wild strain of cellulose-producing bacteria isolated in this work. We show heightened bacterial cellulose production in both static and shake flask fermentation when mutated cellulose synthase is expressed compared to when native cellulose synthase is expressed.Conclusions Our work shows for the first time to our knowledge the in vivo effect when the deregulated mutant variant of cellulose synthase is expressed. This work builds on previous studies and furthers progress towards the goal of creating an optimised cellulose-producing strain capable of commercially viable bacterial cellulose production. The work also highlights the importance of elucidating and disrupting the regulatory mechanisms that govern cellulose synthesis, and the challenging nature of this field.