Abstract: B.hifidunlis one species of bifidobacteria living in the human large intestine.The in vitro studies on B.bifidum are usually performed in submerged fermentation (SmF) system.xt.hich is not true real gut environment.In this patper the growth characteristics of B.bifidum in solid state fermentation (SSF) system (water content of media.54.5% and 68.8%).compared ti,ith SmF were studied.The results show:(1) Besides lactic acid(LA)and acetic acid (AA) B.billdum in SSF secretes propionic acid (PA) and butyric acid (BA).however it only produces LA and AA in SmF .It is assumde that in human large intestine B.bifidum can secretes PA and BA. which appear to be beneficial ic regulate microeubiosis and to improve the human health. The ratio of LA to AA in SSF (1 .26 ~ 1 .62: 1) differs from that in SmF(1 .2) .(2) In SSF cell membrane fatty acids measured at the twelfth hour of fermentation show increased levels of C 16: 0 and C 18: 1 and decreased level of C 18:0 These changes may be related to the production of PA and BA .(3)There are a lower growth rapid.a less viable count longer logarithmic growth phase and death phase for B.bifidum cultivated in SSF than those in SmF.

Key words: Bifidobacterium bifidum, Solid state fermentation, Propionic acid, Butyric acid, Membrane fatty acid