3.4.1 Preparation of immobilized yeast cells
Of the various methods used for continuous fermentation, that
employing the use of immobilized yeast cells was selected. Methods of yeast
immobilization evaluated included collagen casting, acetic acid-lactic acid
cellulose microencapsulation, chitosan/glutar-aldehyde molding,
carrageenan-entrapping method, and calcium alginate gel-entrapping. Of these,
the calcium alginate gel-entrapping method was preferred because of its high
enzymatic activity, simple manner of preparation, and stability.
Preparation of a uniform calcium alginate gel, necessitated
maintaining the viscosity of the mixture of calcium alginate and yeast cells
between 1000 and 2000 cps. The addition of a nonionic surfactant and an
unsaturated fatty acid at the time of gelling was also found to improve cell
retention and enzyme activity. Preparation of immobilized yeast cells is
outlined in Fig 3-15.
Figure 3.15 - Immobilization of