THE EFFECT OF VARIED TEMPERATURE ON THE KINETICS OF METABOLISM OF GIBBERELLA FUJIKUROI IN STIRRED CULTURE

Abstract

The metabolism of Gibberclla Jujikuroi in stirred culture has been studied at varied temperatures over the range 8–40 °C. Two nitrogen-limited media were used, which differed only in the initial concentration of ammonium tartrate. Economic and rate constants have been derived at each stage of fermentation, and methods of relating these to temperature discussed. Each has been related to temperature both by a linear plot, and according to the Van"t Hoff – Arrhenius model.There was no significant difference between the results from the two media early in fermentation. During the storage and maintenance phases all specific rates were considerably lower on the more concentrated medium.The minimum temperature for growth was below 8 °C. Many parameters showed a discontinuity in the range 17–20 °C, and most optima were in the range 29–32 °C. At 38 °C growth ceased when the dry weight was about 2 mg/g of unfiltered broth, and no growth occurred at 40 °C.The contribution of nitrogen to dry weight was virtually independent of temperature. The glucose contribution tended to decrease slightly with increasing temperature over the whole range. The phosphate contribution was constant in the range 8–20 °C, and decreased greatly with increasing temperature from 20 to 36 °C. The magnesium contribution decreased markedly with increasing temperature over the whole range.Two general forms of relation between rate constants and temperature were found. One, a typical "skew" curve with "tail-off' at the lower temperatures, was obtained with the specific growth rate, the nitrogen and glucose quotients, the specific rate of glucose uptake in the maintenance phase, and the gibberellic acid productivity. The second relation showed a marked discontinuity in the range 17–20 °C, above which the increase with increasing temperature was less than at the lower temperatures. This form of curve was obtained with the phosphate, magnesium, and carbohydrate quotients, the linear growth rate, the rate of increase in mycelial dry weight, fat and carbohydrate in the storage phase, and the rate of glucose, phosphate, and magnesium uptake in the same period.