35] Large-scale production of photo-cross-linkable resin-immobilized yeast and its application to industrial ethanol production

Abstract

This chapter describes the technology for a continuous ethanol fermentation process developed by means of immobilized living cells using yeast cells and specially designed artificial resins. Yeast that has the ability to make ethanol was screened from Saccharomyces genus and mixed with prepolymers of photo-cross-linkable resin, then it was illuminated with an active ray (for example, chemical lamp) to change the prepolymers into three-dimensional cross-linked polymers in which yeast was entrapped. The fermentation temperature was kept at about 30–32° and the pH at 4–5. As a result of a bench-scale test (10 liters of ethanol a day) and pilot plant test (250 liters of ethanol a day), the constant activity of the yeast and high ethanol yield on sugar during long-term operation were confirmed, and it was also established that the ethanol productivity was several times that of conventional suspended-state batch system fermentation. Research work on alcohol fermentation using immobilized microorganisms has recently been reported by a number of researchers. Tabulation in the chapter shows ethanol production by different immobilization processes reported by these researchers as compared with conventional process in which yeast cells are not immobilized.