Aims: To maximize spore production by Bacillus amyloliquefaciens B128, and its antagonism to the fungal pathogen Botrytis elliptica B061. Methods and Results: In the 5-l stirred-tank bioreactor (STR), with the 0.5 vvm aeration rate, an agitation rate of 200 rev min(-1) significantly enhanced the spore yield compared to the same in 300 rev min(-1) cultivations. In a 20-l airlift bioreactor (ALR) the maximal spore production was further increased with a controlled aeration rate of 2.5 vvm operated in a 24-mesh net-draft tube mode, and no pH control cultivation. This spore yield in the 20-l ALR was five- and eightfold higher; in addition the cultivation period was 19 h shorter, compared to that obtained from shaker flask and in the 5-l STR cultivations respectively. Conclusions: Although culture conditions are still to be optimized, by using an ALR with net-draft tube, a scaling up from shaker flasks and STR to ALR of spore production by the strain B128 is technically feasible. Significance and Impact of the Study: The spore yields obtained using bioreactors were much higher than those previously reported. The freshly produced spore preparations from the B128 strain significantly antagonized the grey mould pathogen B. elliptica.