FACTORS AFFECTING GIBBERELLIC-ACID PRODUCTION BY FUSARIUM-MONILIFORMEIN SOLID-STATE CULTIVATION ON STARCH

The production of gibberellic acid (GA3) by Fusarium moniliforme M-712 1 in solid-state culture was evaluated in flask cultures as well as in 3-l horizontal rotary reactors. The highest production rate of GA3 wa s with 80% (w/v) maize flour mixed with wheat bran. The optimum initia l moisture content was inversely dependent on the ambient relative hum idity. The initial water activity range for optimal growth and GA3 acc umulation was about 0.98 to 0.99, which is unusually high for a filame ntous fungus. A low O2 concentration resulted in a much decreased GA3 yield and the appearance of a yellow to reddish pigmentation in the my celium. The lag phase was short and rapid growth continued for up to 2 days in the rotary reactor, with a maximum specific growth rate of 0. 12 h-1. The maximum rate of GA3 production occurred during the subsequ ent 3 to 10 days of incubation and the final GA3 concentration reached was 18.7 mg to 19.3 mg/g dry culture. The point of maximum GA3 accumu lation after 10 to 12 days of incubation was usually marked by a sharp increase in pH.