Thermokinetic investigation of effect of temperature on optimum NaCl concentration for petroleum bacterial growth

The power–time curves of growth of three strains of petroleum bacteria at different NaCl concentrations at 40.0 and 50.0 °C have been determined by using a 2277 Thermometric Thermal Activity Analyser. An equation of a power–time curve, ln[αPK/P(t)−1]=ln[(αK−N0)/N0]−αkt, was established based on the generalized logistic equation, where P(t) is the thermal power at time t, K the carrying capacity, PK=P0K, P0 the thermal power of one cell, N0 the bacterial population at time zero, α=(k−D)/k. The method of four observed points with the same time interval was used to calculate the value of PK. The growth rate constant k and the death rate constant D were calculated. The NaCl concentration of optimum growth rate of petroleum bacteria at 40.0 and 50.0 °C, respectively, have been obtained according to the curves k−D versus NaCl concentration, which are 0.26, 0.54 and 0.57 mol l−1 for B-1, B-2 and B-3, respectively, at 50.0 °C, 0.26, 0.55 and 0.56 mol l−1 for B-1, B-2 and B-3, respectively, at 40.0 °C. The results indicated that the effect of temperature on NaCl concentration of optimum growth rate was small.