Efficient Production of Lactobionic Acid Using Capable of Synthesizing Pyrroloquinoline Quinone.

Lactobionic acid (LBA) is an emerging chemical that has been widely utilized in food, cosmetic, and pharmaceutical industries. We sought to produce LBA using . LBA can be produced from lactose in , which is innately unable to produce LBA, by coexpressing a heterologous quinoprotein glucose dehydrogenase (GDH) and a pyrroloquinoline quinone (PQQ) synthesis gene cluster. Using a recombinant strain, we successfully produced LBA without additional supplementation of PQQ, and changing the type of heterologous GDH improved the LBA production titer and productivity. To further enhance LBA production, culture conditions, such as growth temperature and isopropyl-β-d-1-thiogalactopyranoside concentration, were optimized. Using optimized culture conditions, batch fermentation of the recombinant strain was performed using a 5 L bioreactor. After fermentation, this strain produced an LBA titer of 209.3 g/L, a yield of 100%, and a productivity of 1.45 g/L/h. To our best knowledge, this is the first study to produce LBA using heterologous GDH in an strain without any additional cofactors. Our results provide a simple method to produce LBA from lactose in a naturally non-LBA-producing bacterium and lay the groundwork for highly efficient LBA production in , which is one of the most versatile metabolite-producing bacterial hosts.