The thermotolerant, ethanol-producing yeast strain, Kluyveromyces marxianus IMB3, has been immobilized in calcium alginate matrices. The ability of the biocatalyst to produce ethanol from cane molasses originating in Guatemala, Honduras, Senegal, Guyana and the Philippines was examined. In each case the molasses was diluted to yield a sugar concentration of 140 g/l and fermentations were carried out in batch-fed mode at 45 degrees C. During the first 24 hours, the maximum ethanol concentrations obtained ranged from 43-57 g/l with optimum production on the molasses from Honduras. Ethanol production during subsequent re-feeding of the fermentations at 24-hour intervals over a 120-hour period, decreased steadily to concentrations ranging from 20-36 gn and it was found that ethanol productivity remained highest in fermentations containing the molasses from Guyana. When each set of fermentations was re-fed at 120 h and allowed to continue for 48 h, ethanol production again increased to a maximum with concentrations ranging from 25-52 g/l. It was also found however, that increasing the time between re-feeding at this stage in fermentation had a detrimental effect on the functionality of the biocatalyst.
|Published (in print/issue) - May 1997