The kinetic growth of unialga Chlorella vulgaris was investigated in mixed-culture fed-batch chemos tat reactors, with special reference to temperature and pH. The experiments were carried out at looe to 40 o e, pH was controlled from 3.0 to 11.5 in a series of reactors, and glucose at a concentration of 75 mg/L was fed as the sole source of organic carbon. The maximum growth rate of 0.50 day-I was obtained at pH of about 6.31 to 6.84, and the optimum temperature was 32.4°e. The activation energy of the growth-limiting reaction and the enthalpy change for the enzyme-inactivation reaction were 24.5 and 253.36 kJI mole, respectively. The saturation constants for hydrogen ion, KH' and hydroxyl ion, KoH, were temperature-dependent. At temperatures below optimum, KH increased when temperature increased, but KOH decreased. Above the optimum temperature, KH decreased and KoH increased with temperature. Water Environ. Res.. 69,64 (1997).The pH and temperature are among the important environmental parameters governing the activities and growth rates of algae in waste stabilization ponds. Temperature of the surrounding environment is known to influence the biomass composition, nutrient requirements, nature of metabolism (Pirt, 1971), and the metabolic reaction rates (Novak, 1974) because microorganisms do not have the ability to regulate their internal temperature (Esener et aI., 198]).

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