Metabolic engineering of Agrobacterium sp. ATCC31749 for curdlan production from cellobiose

Curdlan is a commercial polysaccharide made by fermentation of Agrobacterium sp. Its anticipated expansion to larger volume markets demands improvement in its production efficiency. Metabolic engineering for strain improvement has so far been limited due to the lack of genetic tools. This research aimed to identify strong promoters and to engineer a strain that converts cellobiose efficiently to curdlan. Three strong promoters were identified and were used to install an energy-efficient cellobiose phosphorolysis mechanism in a curdlan-producing strain. The engineered strains were shown with enhanced ability to utilize cellobiose, resulting in a 2.5-fold increase in titer. The availability of metabolically engineered strain capable of producing β-glucan from cellobiose paves the way for its production from cellulose. The identified native promoters from Agrobacterium open up opportunities for further metabolic engineering for improved production of curdlan and other products. The success shown here marks the first such metabolic engineering effort in this microbe.