Comparative study between yeasts immobilized on alumina beads and on membranes prepared by two routes

RESUMO

Alumina channeled beads and rough surface membranes prepared from aqueous sols of fibrillar pseudoboehmite are able to immobilize yeasts for ethanol fermentation of sugar solutions. This paper describes comparative results of assays carried out with yeasts immobilized onto alpha-alumina beads and membranes prepared under two different conditions of processing and firing. The fermentation tests evaluated by the decrease of fermentable sugars, referred as Brix degrees per hour, indicated that the yeasts immobilized on beads had similar performance, probably because their surfaces, even being morphologically different, presented the same value of open porosity. One type of membrane (asymmetrical; precursor pseudoboehmite; firing temperature 1,150liC; crystal structure; alpha-alumina) had better performance than the other type (asymmetrical; precursor fibrillar pseudoboehmite plus aluminum hydroxiacetate mixture; 1,150liC; alpha-alumina) because the yeast cells entered into their porous interior through the surface slits, were immobilized and their growth was easier than on the external surface.