Cellulose production from glucose using a glucose dehydrogenase gene (gdh)-deficient mutant of Gluconacetobacter xylinus and its use for bioconversion of sweet potato pulp

A gene fragment encoding a putative pyrroloquinoline quinone glucose dehydrogenase (PQQ GDH) was cloned from a bacterial cellulose (BC)-forming acetic acid bacterium, Gluconacetobacter xylinus (= Acetobacter xylinum) strain BPR2001, which was isolated as a high BC producer when using fructose as the carbon source. A GDH-deficient mutant of strain BPR2001, namely GD-I, was then generated via gene disruption using the cloned gene fragment. Strain GD-I produced no gluconic acid but produced 4.1 g·l−1 of BC aerobically in medium containing glucose as the carbon source. The ability of strain GD-I to convert glucose to BC was approximately 1.7-fold higher than that of the wild type. Strain GD-I was also able to produce 5.0 g·l−1 of BC from a saccharified solution, which was derived from sweet potato pulp by enzymatic saccharification. Supplementation of ethanol during aerobic cultivation further increased the concentration of BC produced by strain GD-I to 7.0 g·l−1. The rate of conversion from glucose to BC under these cultivation conditions was equivalent to that of strain BPR2001 cultivated with fructose as the carbon source.