Investigation of ethanol fermentation in industrial strains of Saccharomyvces cerevisiae

• Main Author: Pornpukdeewattana, Soisuda
• Published: University of Nottingham 2011
• Subjects: 579.563
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588080

The aim of this investigation was to assess the impact of yeast strain, initial glucose concentration and fermentation temperature on fermentation kinetic parameters. In this study two industrial Saccharomyces cereviaise strains were investigated, LAL 7 and Ethanol Red. The strains were hexose utilization competent but could not utilize pentoses. Tolerance was assessed in aerobic and anaerobic conditions to the following fermentation stresses: osmotic stress induced by sorbitol, NaCI and high glucose fermentations; ethanol stress; and thermal stress. It was observed that Ethanol Red was more tolerant than LAL 7 to all conditions applied. However, LAL 7 possessed a greater capacity to utilize glucose and complete attenuation of fermentation at all scales assessed. During fermentation it was noted that viability for LAL 7 was particularly impaired suggesting its suitability for pitch and ditch fermentation practices only. In contrast Ethanol Red was more robust and could potentially be applied to recycled or continuous fermentation practices. Finally a companson was made of the fermentation kinetic parameters exhibited by Ethanol Red and LAL 7 during fermentation at the 5L scale. Although the initial and final viabilities as well as growth rates of both strains differed, completion of fermentation occurred at a similar time and ethanol yields were also similar. Differences in the concentration of trehalose accumulated during fermentation were noted with Ethanol.Red producing more of this intracellular carbohydrate than LAL 7. It is proposed that this reflects the superior stress tolerance of the former and it is suggested that trehalose accumulation may be an effective stress selection criteria for strains for bioethanol fermentation.