Batch production of protein from ethane and ethane-methane mixtures.

A culture of Graphium grows upon natural gas and a mineral salt solution. Ethane is the preferred substrate but methane is co-utilized. A stirred-tank type fermentor was used to study batch growth. Maximum production rate of biomass was 80 mg/liter.hr, at pH 4, using simple synthetic supporting medium with ammonium sulfate as a nitrogen source. This rate was observed after 40 hr of fermentation. A doubling time of 3.7 hr was observed. The corresponding specific growth rate was 0.187 per hr. A magnetic drive fermentor was used to study the effect of continuous recycle of gases in a gas-tight system. The rate of oxygen utilization is approximately 2.1 times higher than for ethane. Oxygen must not be allowed to become limiting in recycle gases. The calculated efficiency of overall biomass synthesis averages 30%. Hyphal and unicellular tissue of Graphium contains 52% protein. It compares favorably with standard FAO protein in its content of amino acids.