Effects of fertilization rate and crop rotation on diazotrophic cyanobacteria in paddy field

Abstract

The best culture medium composition for the production of bikaverin by Gibberella fujikuroi in shake-flasks, i.e. 100 g glucose l−1; 1 g NH4Cl l−1; 2 g rice flour l−1; 5 g KH2PO4 l−1 and 2.5 g MgSO4 l−1, was obtained through a fractional factorial design and then scaled-up to a fluidized bioreactor. The effects of carbon and nitrogen concentrations, inoculum size, aeration, flow rate and bead sizes on batch bikaverin production using immobilized G. fujikuroi in a fluidized bioreactor were determined by an orthogonal experimental design. Concentrations of up to 6.83 g bikaverin l−1 were obtained when the medium contained 100 g glucose l−1 and 1 g NH4Cl l−1 with an inoculum ratio of 10% v/v, an aeration rate of 3 volumes of air per volume of medium min−1, and a bead size of 3 mm. Based on dry weight, the bikaverin production was 30–100 times larger than found in submerged culture and approximately three times larger than reported for solid substrate fermentation.