No abstract

Bacterial cellulose (BC) production was realized in a batch cultivation of Acetobacter xylinum subsp. sucrofermentans BPR2001 in a 50-L internal-loop airlift reactor. When the bacterium was cultivated with air supply, 3.8 g/L of BC was produced after 67 hours. When oxygen-enriched gas was supplied, the concentration of BC was doubled and the production rate of BC was 0.116 g/L. h, which was two times higher than that of air-supplied culture and comparable to that in a mechanically agitated stirred-tank fermentor. Bacterial cellulose produced by the airlift reactor formed a unique ellipse pellet (BC pellet), different from the fibrous form which was produced in an agitated stirred-tank fermentor. The BC-pellet suspension was demonstrated to have a higher volumetric oxygen transfer coefficient than the fibrous BC suspension in a 50-L internal-loop airlift reactor. The mixing time of BC-pellet suspension in the airlift reactor was also shorter than that in water.

Acetan is a water-soluble polysaccharide produced by a bacterial cellulose (BC) producer, Acetobacter xylinum. An acetan-nonproducing mutant, EP1, was generated from wild-type A. xylinum BPR2001 by the disruption of aceA, which may act to catalyze theˆrst step of the acetan biosynthetic pathway in this bacterium. EP1 produced less BC than the wild-type strain. However, when EP1 was cultured in a medium containing acetan, BC production was stimulated and theˆnal yield of BC was equivalent to that of BPR2001. The culture broth containing acetan was more viscous and the free cell number was higher than that of the broth without the polysaccharide, so acetan may hinder the coagulation of BC in the broth. The addition of 1.5 g W l agar also increased BC production; we concluded that acetan and BC syntheses were not directly related on the genetic level.

The new iTACT-HBsAg assay appears to detect total HBsAg with high sensitivity, even in the presence of HBsAb, and may useful in identifying subclinical or occult HBV carriers.

Acetobacter xylinum BPR2001 produces water-insoluble bacterial cellulose (BC) and a water-soluble polysaccharide called acetan in corn steep liquor-fructose medium. Acetobacter xylinum EP1, which is incapable of acetan production was derived by disrupting the aceA gene of BPR2001. The BC production by EP1 (2.88 g/L) was lower than that by BPR2001 (4.6 g/L) in baffled-flask culture. When purified acetan or agar was added to the medium from the start of cultivation, the BC production by EP1 was enhanced and the final BC yield of EP1 was almost the same as that of BPR2001. A similar improvement of BC production by EP1 by the addition of agar was also confirmed by cultivation in a 50-L airlift reactor. From these results, the role of acetan in BC production is associated with the increase in the viscosity of the culture medium which may hinder coagulation of BC and cells in the culture, thereby accelerating the growth of BPR2001 and BC production by BPR2001.