Kinetics and thermodynamics of ethanol production by a thermotolerant mutant of Saccharomyces cerevisiae in a microprocessor-controlled bioreactor

Abstract

Aims: The present investigation deals with the development of thermotolerant mutant strain of yeast for studying enhanced productivity of ethanol from molasses in a fully controlled bioreactor. Methods and Results: The parental culture of Saccharomyces cerevisiae ATCC 26602 was mutated using UV treatment. A single thermotolerant mutant was isolated after extensive screening and optimization, and grown on molasses medium in liquid cultures. The mutant was 1AE45-fold improved than its wild parent with respect to ethanol productivity (7AE2 g l )1 h )1 ), product yield (0AE44 g ethanol g )1 substrate utilized) and specific ethanol yield (19AE0 g ethanol g )1 cells). The improved ethanol productivity was directly correlated with titres of intracellular and extracellular invertase activities. The mutant supported higher volumetric and product yield of ethanol, significantly (P £ 0AE05) higher than the parental and other strains. The mutated cultures produced 1AE8-and 2AE6-fold more extracellular and intracellular invertase productivity, respectively, than that produced by its wild parent at 40°C. Thermodynamic studies revealed that the cell system exerted protection against thermal inactivation during formation of products. Conclusions: A mutant derivative of Sacchromyces cerevisiae with improved productivity of ethanol and invertases has been obtained, which showed concomitant improvement in thermostability of endogenous metabolism for formation of both ethanol and invertases. Significance and Impact of the Study: The results of the present study are of commercial value as the mutant can be used for ethanol production in parts of Pakistan where the temperature may go up to 40°C in April. Ethanol product yield coefficient and volumetric productivity, revealed the hyper-productivity of ethanol from molasses at 40°C, which is not appropriate for wild organism.

Isolation and Identification of Local Ethanol Tolerant Yeast Populating Distillation and Milling Sites in Nigeria

“…The expected differences over the time course may address the integrity of the cell membrane in addition to the organisms' acidification activity. Since the pH optima for both inhibited and uninhibited ethanol fermentation is reported to be about 5.5, the data in this study is in line with established data [24]. In the broth cultures containing varying concentrations of ethanol, there seems to be an addition metabolic by-product that may account for differences in energetic level that helped the cells maintain their physiological state.…”

All-Polyamide Composite Coated-Fabric as an Alternative Material of Construction for Textile-Bioreactors (TBRs)

“…Ethanol yield 96.3% of the theoretical maximum was attained using average ethanol concentration during the stationary phase. Ethanol specific productivity and substrate-specific consumption rate of 4.0 g/L/h and 0.7 g/g/h were attained in the bioreactor, which are comparable to the reported values from sugarcane-based ethanol production facilities [31,32]. …”

Enrichment of a continuous culture of Saccharomyces cerevisiae with the yeast Issatchenkia orientalis in the production of ethanol at increasing temperatures

“…In the present work, I. orientalis was able to perform cell division and to produce ethanol at temperatures in which the cell division and ethanol production by S. cerevisiae (>40°C) were increasingly constrained. As P. membranifaciens and I. orientalis are not able to assimilate sucrose [3], the propagation of these two yeasts in sugarcane syrup having sucrose as the main carbon source depends on the production of invertase by S. cerevisiae [32]. Saccharomyces cerevisiae is known to produce the highest levels of ethanol within the range of 30-35°C, while the capability of producing ethanol from glucose by I. orientalis was maximal at 42°C as shown in the present work.…”