(A) The R-AFP yields of different expression times from the same batch. (B) Optimization of R-AFP expression in different inocula. Sf9 cells were grown in 1-litre shaking flasks to exponential phase (2 × 106 cells/ml). The virus titres were 2 × 107 pfu/ml, with different volumes of the infectious baculovirus inocula (1:50, 1:100 and 1:500) and were monitored at different times (0, 24, 48, 72 and 96 h). R-AFP protein expression reached the highest level of approximately 1.5 mg/l at a 1:100 volume of the infectious baculovirus inocula when harvested at 96 h post-infection. n=10, *P<0.05 compared with different infectious baculovirus inoculas 1:500 volume groups.