SCREENING OF A STRAIN OF GIBBERELLA-FUJIKUROI FOR IMPROVED MICROBIAL CONVERSION OF (-)-KAURENE

To increase the amounts of gibberellins produced by the microbial conv ersion of (-)-kaurene with Gibberella fujikuroi, a screening of ten G. fujikuroi strains was conducted. The G. fujikuroi IFO 9977 strain was found to lead to the largest yields of gibberellins. The formation of gibberellins from (-)-kaurene with the IFO 9977 strain was 1.4 times larger than obtained with the IFO 30337 strain which previously was fo und to produce the largest conversion. The biological activities of th e gibberellins from (-)-kaurene with the IFO 9977 strain, as indicated by the elongation of the second leaf sheath of dwarf rice, tan-ginbou zu (Oryza sativa L. cv.), were the most of the ten strains used. Furth ermore, the effect of the substrate concentration on the formations of gibberellins also was investigated using the most active strain indic ated by the screening tests. Gibberellin formations decreased with inc reasing substrate concentrations in the culture medium.