High-level production of maltobionic acid from high-maltose corn syrup by genetically engineered Pseudomonas taetrolens

Maltobionic acid (MBA) has recently emerged as an important material in various industries. Here, we showed that quinoprotein glucose dehydrogenase (GDH) from Pseudomonas taetrolens could convert maltose into MBA by heterologously expressing this enzyme in MBA non-producing Escherichia coli. We homologously expressed GDH in P. taetrolens to improve intracellular maltose-oxidizing activity and MBA production. We optimized culture conditions, then applied these conditions to batch fermentation by recombinant P. taetrolens in a 5-L bioreactor. The MBA production, yield, and productivity of batch fermentation using high-maltose corn syrup (HMCS), an inexpensive maltose source, were 200 g/L, 95.6 %, and 6.67 g/L/h, respectively. Although the MBA productivity from HMCS was 70.1 % of that compared with pure maltose as the substrate, HMCS was a better substrate for commercial MBA production, considering the cost was 1.1 % of that of pure maltose. The present findings provide an economically feasible strategy with which to produce MBA.