Enhancement of Lactobionic Acid Productivity by Homologous Expression of Quinoprotein Glucose Dehydrogenase in .

This is the first study on improving lactobionic acid (LBA) production capacity in by genetic engineering. First, quinoprotein glucose dehydrogenase (GDH) was identified as the lactose-oxidizing enzyme of . Of the two types of GDH genes in , membrane-bound (GDH1) and soluble (GDH2), only GDH1 showed lactose-oxidizing activity. Next, the genetic tool system for was developed based on the pDSK519 plasmid for the first time, and GDH1 gene was homologously expressed in . Recombinant expression of the GDH1 gene enhanced intracellular lactose-oxidizing activity and LBA production of in flask culture. In batch fermentation of the recombinant using a 5 L bioreactor, the LBA productivity of the recombinant was approximately 17% higher (8.70 g/(L h)) than that of the wild type (7.41 g/(L h)). The LBA productivity in this study is the highest ever reported using bacteria as production strains for LBA.