Effect of Culture Conditions on Cellulose Production by a Komagataeibacter xylinus Strain

Bacterial cellulose (BC) is an abundant biopolymer with a wide range of potential industrial applications. However, the industrial application of BC has been hampered by inefficient production. This study aims to investigate the influence of a spontaneous mutation that results in decreased cellulose production by a Komagataeibacter xylinus strain. The yields of cellulose are significantly different under different culture conditions, which imply that the shearing force is responsible for the selection of spontaneous mutants. Fermenter culture conditions under shake-flask culture conditions are further simulated. The shearing force activates the conversion of microbial cells to Cel(-) mutants, and the accumulation of water-soluble exopolysaccharides is observed. The Cel(+) cells under agitated culture are not easily converted into Cel(-) mutants upon the addition of water-soluble exopolysaccharides synthesized by K. xylinus and a viscous polysaccharide, such as xanthan gum. The conversion ratio of Cel(+) cells to Cel(-) mutants is strongly related to the shearing force and viscosity of the fermentation broth. The synthetic pathways of bacterial cellulose and water-soluble polysaccharides are independent of each other at the genetic level. However, a substrate competitive relationship between these two polysaccharides is found, which is significant in terms of the optimization of cellulose production in commercial processes.