Abstract
Problem Statement: Some component of fermentation medium showed to reduce the Saccharomyces cerivisae production of ethanol. Approach: This study was designed to evaluate the role of some fermentation parameters in affecting ethanol productivity from beet molasses BM by Saccharomyces cerevisiae CAIM13. Results: Increase in cell concentration (inoculums size) of the yeast above 3.6×105 cells/100 mL decreased the ethanol yield. The yeast could tolerate ethanol concentration up to 10% but failed to grow at concentration of 12 and 15%. Employment of a bench-scale tank fermenter enhanced the fermentation efficiency. 77% of BM sugars were assimilated after 48h giving a concentration of 5.4% ethanol. Utilization of a cell-recycling technique showed that the tested organism was capable of performing four fermentation cycles. The mud-free, H2SO4-treated beet molasses TBM was superior to sucrose in the repeated batch fermentation technique. A continuous-flow fermentation technique employing immobilized yeast cells yielded maximum ethanol productivity after 6 days. Conclusion: The present investigation has demonstrated the importance of some fermentation parameters in improving the alcoholic fermentation technology of BM. When free cells of S. cerevisiae. In the case of immobilized cells, the continuous-flow technique speared superior to the repeated batch-fermentation technique in production of alcohol from TBM.
Highlights
MATERLALS AND METHODSDuring recent years, production of ethanol by fermentation on a large scale has been of considerable interest to meet to increased demand for new sources of energy (Akhir et al, 2009; Turhan et al, 2010)
Cell-recycling technique: The yeast obtained after 48h in the stirred–tank fomenter was allowed to settle, the supernatant culture broth was siphoned off and 4liters of fresh fermentation medium were added under aseptic conditions
The utilization of a cell-recycling technique showed that test organism was capable of performing 4 fermentation cycles and that relatively high fermentative activity was attained in the first reuse of the cells Table 3
Summary
Production of ethanol by fermentation on a large scale has been of considerable interest to meet to increased demand for new sources of energy (Akhir et al, 2009; Turhan et al, 2010). Preparation of yeast inoculum’s: To initiate yeast growth, inocula from 3day old slants were transferred to 250 mL Erlenmeyer flasks, each containing 50 mL of a medium composed of (g L−1): glucose 10, peptone 5, yeast extract, malt extract 3. Cell-recycling technique: The yeast obtained after 48h in the stirred–tank fomenter was allowed to settle, the supernatant culture broth was siphoned off and 4liters of fresh fermentation medium were added under aseptic conditions. Aeration and stirring rates were reduced to 0.5 L min−1 and 100rpm at the end of 24 h incubation at 30oC when good yeast growth was usually observed. The utilization of a cell-recycling technique showed that test organism was capable of performing 4 fermentation cycles and that relatively high fermentative activity was attained in the first reuse of the cells Table 3 Under these conditions, the added sugars were almost totally assimilated with the
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