Production of bacterial cellulose by Acetobacter xylinum BPR2001 using molasses medium in a jar fermentor.

Bacterial cellulose (BC) production by Acetobacter xylinum subsp. sucrofermentans BPR2001 using molasses medium was carried out in a jar fermentor. When molasses was subjected to H(2)SO(4)-heat treatment, the maximum BC concentration increased to 76% more than that achieved using untreated molasses, and the specific growth rate increased 2-fold. When the initial sugar concentrations in the H(2)SO(4)-heat treated molasses were varied from 23 g/l to 72 g/l, BC concentration, production rate, and yield were maximum at sugar concentrations of 23 g/l and 37 g/l, and production of by-products, such as polysaccharides and CO(2), was lower than at sugar concentrations of 48 g/l and 72 g/l, indicating that maintaining a lower molasses concentration is essential for efficient BC production in jar fermentors, this being due mainly to the complex nature of molasses. Molasses has a clear advantage over pure sugars as a carbon source from an economic viewpoint.

Features of bacterial cellulose synthesis in a mutant generated by disruption of the diguanylate cyclase 1 gene of Acetobacter xylinum BPR 2001.

The diguanylate cyclase 1 (DGC1) (dgc1) gene in Acetobacter xylinum BPR 2001--a bacterial cellulose (BC) producer--was cloned and sequenced, and a DGC1 gene-disrupted mutant, strain DD, was constructed. The production and structural characteristics of the BC formed by DD were compared with those of the parental strain BPR 2001. BC production by DD was almost the same as that by BPR 2001 in static cultivation and in shake flask cultivation. However, in a jar fermentor DD produced about 36% more BC than the parental strain. DD produced suspended particle materials that cannot aggregate owing to their random structural characteristics in static cultivation; more uniformly dispersed BC pellicles and smaller BC pellets are produced on average in a jar fermentor, as reflected by the higher BC production by DD than by the parental strain in a jar fermentor. Micrographs of BC produced by DD revealed that the width of cellulose ribbons assemblies decreased as a result of differences in the ultrastructure and mechanism of formation of BC between the two strains. These results reveal that disruption of the dgc1 gene, which catalyzes synthesis of c-di-GMP (an effector of BC synthase), is not fatal for BC synthesis, although it affects BC structure.