Isolation of noninhibitory strains of Zymonomas mobilis

Zymononas mobilis is a potentially useful organism for commercial biological ethanol production. Z. mobilis has the ability to antagonize the growth of a wide variety of bacteria and fungi. The factor(s) responsible is a low-molecular-weight, agar-diffusible, heat- and protease-resistant, broad-spectrum activity which is produced by all strains tested. A Z. mobilis strain lacking the ability to inhibit other microorganism would be of obvious value. The authors describe the use of N-methyl-N'-nitro-N-nitrosoguanidine to derive such isolates from a wild-type strain. Although the underlying genetic basis is unknown, the isolation of noninhibitory strains is the first step in the genetic analysis of growth inhibition caused by Z. mobilis . Intergeneric inhibition may have important consequences for the industrial application of Z. mobilis . If growth-inhibibitory factors are produced during fermentation, Z. mobilis may have detrimental effects on a coculture system at the expense of productivity.