Behaviour of Saccharomyces cerevisiae cells entrapped in a polyacrylamide gel and performing alcoholic fermentation

Summary The behaviour of Saccharomyces cerevisiae cells entrapped in a polyacrylamide gel was studied during their continuous function in an ethanol-producing reactor. Polymerization destroys 40% to 80% of the cells, depending on their physiological state. A three day adaptation phase is required before ethanol production stabilizes and this phase corresponds to an increase in cell concentration in the gels and to protein synthesis. The amounts of DNA, glucan, glycogen and trehalose are different in entrapped and free cells. Microscopic observation shows that 75% to 85% of the cells lose their integrity and that the remainder appear to multiply normally. Within a gel particle, both viability and fermentation activity are heterogeneous. A high percentage of cells have low viability and low fermentation activity. A proportion of cells remains capable of forming colonies and these cells have higher fermentation activity and are preferentially localized at the surface of gel particles.