INFLUENCE OF ETHANOL ON THE HOPANOID CONTENT AND THE FATTY-ACID PATTERN IN BATCH AND CONTINUOUS CULTURES OF ZYMOMONAS-MOBILIS

By TLC, GLC and mass spectrometric methods, 1,2,3,4-tetrahydroxypentane-29-hopane (THBH) was shown to occur in Z. mobilis. This compound contributed up to 20% to the total lipids. The fatty acid pattern and the content of hopanoids (hopene, hopanol and THBH) were determined in batch and continuous cultures. In late exponential cells from batch cultures the relative amount of palmitic acid was increased partially at the expense of cis-vaccenic acid, when the initial glucose concentrations were increased. In a batch culture, THBH reached a maximum value in the early exponential growth phase. In an anaerobic continuous culture with a low glucose feed concentration, the THBH content and the relative amount of cis-vaccenic acid were low. The contribution of both compounds increased strongly with increasing glucose feed concentrations (i.e., at higher steady-state ethanol concentrations). The same result was found with aerobic continuous cultures which produced significant amounts of acetaldehyde and acetic acid, in addition to ethanol and CO2. The stability and permeability of the cytoplasmic membrane of the ethanol-producing bacterium Z. mobilis was regulated by variations in the distribution of hopanoids and fatty acids.