The selection and characterization of Zymomonas mobilis for ethanol production from Jerusalem artichoke (Helianthus tuberosus L.) juice was investigated. Growth and ethanol production of four Z. mobilis strains isolated in Thailand, that is, TISTR 405, TISTR 548, TISTR 550 and TISTR 551, were compared with those of the type strain Z. mobilis ZM4 (NRRL B-14023) at different temperatures. Among the strains tested, TISTR 548 gave the highest ethanol concentration at 30 to 35°C, as compared to the others. Therefore, this strain was chosen for ethanol production from Jerusalem artichoke juice after acid hydrolysis. The influence of some fermentation factors such as sugar concentration, pH of the fermentation medium, inoculation size and nitrogen source on ethanol production from Jerusalem artichoke juice was determined. The results show that the maximum ethanol concentration (95.9 g/L) with 98% of the theoretical ethanol yield was obtained when the fermentation was carried out in a medium containing 250 g/L total sugars, pH 5.0, inoculation size at 10% and using 0.5 g/L diammonium phosphate as nitrogen source. The maximum theoretical ethanol yield obtained in this study was higher than those previously reported.
Key words: Ethanol production, Zymomonas mobilis, thermotolerant microorganism, Jerusalem artichoke.
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