Fine-tuning the cell morphology of Corynebacterium glutamicum via dual-valve regulation for enhanced hyaluronic acid production

Abstract

Enhanced synthesis of hyaluronic acid (HA) with recombinant Corynebacterium glutamicum as production host is achieved in this work. Hyaluronan synthase (HAS), which is a membrane protein acting as a key enzyme in HA biosynthesis, impacts both HA yield and its molecular weight. Cell morphology, which includes size, shape, and surface area, has a large impact on the expression and activity of HAS. Therefore, deliberate regulation of cell morphology holds the potential to enhance HA production. Here, we constructed three modules, namely the transporter module, the morphology tuning module and the HA synthesis module. The transporter module contains a strong constitutive promoter Ptuf and arabinose transport protein used to control the maximum amount of inducer entering the cell, thus reducing excessive cell deformation. The morphology tuning module contains an arabinose-inducible weak promoter PBAD and a cell-division-relevant gene used to sense intracellular inducer concentrations and achieve different degrees of change in cell size. These two modules work together, described as a dual-valve regulation, to achieve fine-tuning of cell morphology, resulting in a 1.87-fold increase in cell length and a 2.08-fold increase in cell membrane. When combined with the HA synthesis module, the HA titer reached 16.0 g/L, which is 1.6 times the yield reported in the previous morphology-engineered strain. Hence, for the first time, a morphologically engineered strain resulting in both high cell density and HA titer was constructed.