An obligatory type II methanotroph Methylosinus trichosporium OB3b was cultivated on methanol as a sole carbon and energy source. The effects of methanol concentration, pH, temperature, nitrogen source and phosphate concentration on cell growth were investigated and the results were compared with the growth on methane which had been studied previously. When (NH,),SO, was used as a nitro gen source, the maximal specific growth rate (p,,,,,) on methanol was 0.20hr-´ and the carbon conversion efficiency(CCE) was 43%. In comparison, on methane, A4,,,, and CCE were 0.08hr-´ and 32%, respectively. Ammonia was found to be a better nitrogen source for methanol-growing cells. Cell yielc on nitrogen(YX/) was the same regardless of nitrogen source as 7.14g dry cells/g N, but the yield or ´methanol(Yx1) was higher with ammonia(0.8g dry cells/g MeOH) than with nitrate(0.64g dry cells/€ MeOH). Optimal pH and temperature were 7.0 and 301C, respectively. Methanol inhibition on cel growth was observed at above 0.5%(v/v). Inhibition by phosphate was observed at above 60mM although the inhibition on methanol dehydrogenase activity started at a much lower level of 20mM.
Based on the experimental findings, the cellular physiology of M. trichosporium OB3b growing on the two closely-related carbon sources were discussed extensively.
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