Effects of temperature and pH on the kinetic growth of unialga Chlorella vulgaris cultures containing bacteria

Abstract

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]).

Engineering Aspects Related to the Use of Microalgae for Biofuel Production and CO2 Capture from Flue Gases

“…As it can be observed from Fig. 6, the kinetic model proposed by Mayo (1997) well describes the fact that each strain of microalgae has a relatively narrow optimal range of pH and most microalgal species are favored by neutral pH.…”

“…However, pH variation not only represents a fundamental indicator of the evolution of photosynthetic activity but can also, in turn, strongly affect the growth kinetics of microalgae influencing the distribution of carbon dioxide species and carbon availability thus causing direct physiological effects (Cornet et al 1995;Chen and Durbin 1994). Moreover, in microalgal cultures, the hydrogen ion is recognized to be a noncompetitive inhibitor near neutral conditions, while it can limit photosynthetic growth and substrate utilization rates at very low or very high pH levels (Mayo 1997). Furthermore, pH can affect the enzymatic activity of intra-and extracellular carbonic anhydrase, thus influencing the carbon capture mechanism of some microalgal strains (Concas et al 2012).…”

“…Furthermore, pH can affect the enzymatic activity of intra-and extracellular carbonic anhydrase, thus influencing the carbon capture mechanism of some microalgal strains (Concas et al 2012). In order to evaluate the dependence of growth rate upon pH, the following expression has been proposed by Mayo (1997):…”

“…can be considered as a noncompetitive substrate when the medium pH is high while displays an inhibition effect when the pH of the medium is low (Mayo 1997). The resulting dependence of growth rate from pH is depicted in Fig.…”

Cultivation Of Microalgae (Chlorella vulgaris) For Biodiesel Production

“…Further increase in temperature (38 °C) led to an abrupt interruption of microalgal growth, and later the cells dead. The (20) found that the maximum growth rate was obtained at pH of about 6.31 to 6.84, and the optimum temperature was 32.4 °C. By (21) Ch.…”