Methylosinus trichosporium OB3b oxidized methane to methanol in the presence of a high concentration of Cu2+ Further oxidation of methanol to formaldehyde was prevented by adding 200 mm NaCl which acted as a methanol dehydrogenase H inhibitor. The bacterium, 0.6 mg dry cell ml(-1), in methane/air (1:4, v/v) at 25degreesC in 12.9 mM phosphate buffer (pH 7) containing 20 mm sodium formate and 200 mm NaCl accumulated 7.7 mM methanol over 36 h.