Cell yields of bacteria grown on methane.

Several mixed cultures of methane-oxidizing bacteria have been isolated. Among them, culture HR (consisting of two gram-negative rods, one 0.5 x 1.0 mu, the other 0.8 x 2 to 3 mu) was found to be the fastest-growing and to give the highest yields. Optimal conditions for rapid growth and high cell yields from methane were found to be: 30 C, NH(4) as nitrogen source, and pH 6.5. Requirements for CO(2) and Cu were observed. Under these conditions, generation times of approximately 3 hr and cell yields from methane between 65 and 70% could be attained. Culture HR can utilize methane, methanol, ethyl alcohol, 1-propanol, n-butyl alcohol, and glucose, but not propane, for growth. Yeast and beef extracts are inhibitory. Carbon balances demonstrate that few if any products other than cells and CO(2) are produced from methane under the growth conditions used. Cell analyses for carbon, hydrogen, nitrogen, and amino acid content of culture HR were also made.