Production of a Gaseous Saturated-hydrocarbon Mixture by Rhizopus japonicus under Aerobic Conditions

The microbial production, by the genus Rhizopus, of a gaseous saturated-hydrocarbon mixture was studied under aerobic conditions. Rhizopus strains, comprising 13 strains of 9 species, were tested as to their ability to produce a gaseous hydrocarbon mixture. Except for one strain, all the strains tested produced more than two kinds of gaseous hydrocarbons simultaneously when grown in nutrient broth containing glucose. Rhizopus japonicus IFO 4758 was selected as being typical of these producers of mixed gaseous hydrocarbons. When this organism was cultivated in a synthetic medium supplemented with l-cysteine under aerobic conditions, the maximum production of the total gaseous hydrocarbon mixture reached ca. 10 nl/ml culture broth/hr. The gaseous hydrocarbon mixture produced was composed mainly of paraffin hydrocarbons, i.e., ca. 74% pentane, ca. 16% propane and a trace amount of methane. The ratios of saturated to unsaturated, and even to odd number hydrocarbons produced by this fungus were 95 : 5 and 90: 10, respectively. The biosynthetic pathways for the production of these gases are discussed in comparison with the biosynthetic pathways for ethylene and isobutene in microorganisms.