EFFECTS OF C N RATIO, N-CONTENT, PH, AND INCUBATION-TIME ON GROWTH AND GIBBERELLIN PRODUCTION BY AZOSPIRILLUM-LIPOFERUM/

Different C/N ratios did not substantially affect growth of Azospirill um lipoferum Al op 33. However, under an initial concentration of NH4C l 1.25 g l(-1) (C/N ratio 12.5) and pH 6.8, exopolysaccharide producti on was observed. This was correlated with a higher survival of the mic roorganism measured as colony forming units (CFU), and a substantial i ncrease in gibberellin production (426 pg ml(-1) of gibberellin A(3) a ccumulated after 5 d of culture), as measured by capillary gas chromat ography-mass spectrometry-selected ion monitoring (GC-MS-SIM) with deu terated internal standards. The identification of gibberellin A(1) by selected ion monitoring, and of gibberellin A(3) by full spectrum was confirmed. The optimal production of gibberellin A(3) by pure cultures of A Azospirillum lipoferum Al op 33 was obtained by accumulation aft er several days in the stationary phase, under conditions of high viab ility for the bacterium.