The influence of broth exchange ratio on bacterial cellulose (BC) production by repeated-batch culture using Acetobactor xylinum subsp. sucrofermentans BPR3001A was investigated. When repeated-batch cultures were conducted at various broth exchange ratios (a), the highest BC production rate (0.43 g l(-1) h(-1)) and BC yield (28%) were obtained at alpha of 0.9. With a larger alpha than 0.9, the ATP content was lower than that at a of 0.9 and the culture time was prolonged, resulting in a lower BC production rate. On the other hand, with a smaller a than 0.9 the dissolved oxygen could not be maintained at 10% of air saturation and CO2 evolution from fructose increased, resulting in a lower BC yield, whereas the ATP content maintained higher level than that at a of 0.9. When six cycles of repeated-batch culture were conducted with a of 0.9, at least four cycles of repeated-batch culture were possible with a BC production rate of 0.42 g l(-1) h(-1) and a BC yield of 28% on average, and BC productivity was 2.5 times higher than that in single batch culture. (C) 2002 Elsevier Science Ltd. All rights reserved.