Alcoholic fermentation from sweet sorghum: Some operating problems
2000
Strehalano, P. | M.L., Della-Dupuy | Phowchinda, O.(Laboratoire de Genie Chimique, UMR-CNR 5503 (France))
In Thailand, ethanol production from sweet sorghum may be a new option to solve the serious problem of fossil oil, to improve agricultural economy and also to reduce the pollution in environment. Kinetic studies on synthetic medium (single and mixed sugars) showed that the proportion between sugars does not influence the behaviour of the selected yeast., Saccharomyces cerevisiae. The initial concentration of inoculum from three levels, 3.10**(6), 10.16**(6), 15.10**(6), cells/mL were experimented to find a good economical compromise. The 10.16**(6) cells/mL initial inoculation seems to be a suitable concentration for the industrial process. In the same context, the kinetics of sugar consumption and ethanol production from different cycles (runs with 3.10**(6) and 15.10**(6) cell/mL intial concentration) showed the stability of the selected strain. In order to use sweet sorghum juice as a fermentation substrate, the concentrations between pure culture of S. cerevisiae and a contaminous yeast, Brettanomyces bruxellensis, were tested on glucose 50 g/L. S. cerevisiae always succeeded in implantation more than 50 percent but Brettanomyces bruxellensis has never dissappeared form the medium (minimum 5 to 10 percent). Then 150 g/L glucose concentration was used, and S. cerevisiae was inoculated during the lag period of the contaminant, if was found that S. cerevisiae could not develop more than 10.16**(6) cells/mL. To avoid contamination, the different growth kinetics of both strains must be considered. The experiment showed that operating methods and process control greatly influence the contamination implantation.
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