Production of recombinant β -galactosidase derived from Lactobacillus plantarum by Pichia pastoris was investigated in 5 -L bioreactor. A kinetic model of methanol feeding at the exponential rate was established and the effect of specific growth rate on the β -galactosidase production was examined. In methanol induction phase, four specific growth rates, 0.010/h, 0.029/ h, 0.043/h and 0.058/h, were investigated. The specific growth rate was found to play a significant role on the β-galactosidase production. The maximum β-galactosidase production (60 U/mL) was achieved at a specific growth rate of 0.029/h. Compared with the regular feeding strategy, the exponential feeding of methanol could afford higher β-galactosidase production, especially during
the later stage of methanol induction.