Degree of Polymerization of Cellulose from Acetobacter xylinum BPR2001 Decreased by Cellulase Produced by the Strain

Abstract

Acetobacter xylinum produces both cellulase and bacterial cellulose, but some report believed that this cellulase activity does not decrease the degree of polymerization (DP) of bacterial cellulose during cultivation. A. xylinum subsp. sucrofermentans BPR2001 produces two enzymes that hydrolyze CM-cellulose and cellotriose, respectively. We examined the effect of the two cellulase activities on the DP of bacterial cellulose when bacterial cells were cultured with agitation at pH 4, where little cellulase is produced, and at pH 5, where much cellulase is produced. The weight-average degree of polymerization (DP_w) of bacterial cellulose remained in the range of 14, 000 of 16, 000 during cultivation at pH 4, but at pH 5, the DP_w decreased from 16, 800 to 11, 000. The mechanical strength of a sheet prepared from the bacterial cellulose produced at pH 4 was higher than those of BC produced at pH 5. These results suggest that the two cellulase activities cause the decrease in DP and deterioration of physical properties of bacterial cellulose seen during cultibation.