Vitreoscilla hemoglobin (VHb) gene driven by the constitutive bla promoter was expressed in the cellulose-producing Acetobacter xylinum. The expressed VHb was biochemically active and could enhance cell growth in a shaken culture containing cellulase. VHb-expressing A. xylinum (VHb(+)) exhibited a specific growth rate 50% higher than that of the host strain (VHb(-)). Probably because of its faster growth rate, the size of tentacled cellulose beads produced by VHb(+) was about 20% of that produced by VHb(-) after 2 days cultivation in a shake-flask. When cultured statically, the amount of cellulose pellicle produced by VHb(+) could be 2-fold that produced by VHb(-). Cellulose pellicle concentration of 11 g/L was obtained for VHb(+), whereas 6 g/L was obtained for VHb- after 6 days of microaerobic incubation.