THERMOTOLERANCE OF ENCAPSULATED YEAST

There is a growing concern about the enhanced global warming caused by excessive CO2 emissions. Therefore alternative fuels are in focus today in order to replace fossil fuels. Production of bioethanol by fermentation can be a suitable substitute for fossil fuel, if it can be produced from lignocellulosic materials. However, there are still several problems to solve before second generation bioethanol can be produced in a stable and economically feasible way. One problem is e.g. the thermotolerance of Saccharomyces cerevisiae, which is the most commonly used yeast for ethanol production. Yeast with high thermotolerance is desirable especially in tropical countries where cooling is today necessary to keep the reactor at an appropriate temperature, and also in simultaneous saccharification and fermentation processes where the enzymes which work together with the yeast have an optimal temperature which is higher than the yeast can survive. Our group is investigating the effect encapsulation has on yeast. The yeast is enveloped inside spherical polyelectrolyte membranes, where the cells are kept close together in capsules of approximately 4 mm in diameter (Figure 1). Previous studies have shown that the encapsulated yeast is more tolerant against inhibitors and we have now also shown that the encapsulated yeast become more thermotolerant