Abstract
Two thermotolerant methylotrophic bacterial isolates (EM1, EM2) capable of growing in mineral salts medium, containing 50 mM methanol as the sole carbon and energy source, were studied. The maximum specific growth rates of EM1 and EM2 in batch culture were 1.39 h⁻¹ and 0.8 h⁻¹, respectively. Growth of the two tested microorganisms was influenced by different growth conditions, including methanol concentration, temperature, and pH values. They differed in their tolerance to methanol concentration. The optimum growth temperature of EM1 and EM2 were 50°C and 55°C, respectively. The highest specific growth rate (µmax) of EM1 and EM2 were observed at the optimum pH 7.4 and 8.0, respectively. In chemostat continuous culture of the isolate EM1, there was an increment in the different growth parameters; methanol concentration, oxygen consumption, and CO₂ production. Moreover, the metabolic and cell growth rate monitored as cell dry weight (mg/ml) and protein content in whole cells were also increased.