title: Corn starch gel for yeast cell entrapment. A view for catalysis of wine fermentation.
abstract: A new biocatalyst was prepared by immobilization of Saccharomyces cerevisiae AXAZ-1 yeast cells in the matrix of corn starch gel. This biocatalyst was used for repeated batch fermentations of glucose and grape must at various sugar concentrations (110-280 g/L) and low-temperature winemaking (5 degrees C). The biocatalyst retained its operational stability for a long period, and it was proved to be capable of producing dry and semisweet wines. The produced wines were analyzed for volatile byproducts by GC and GC-MS, and the results showed an increase in the number and amount of esters by immobilized cells. In addition, an increase in the percentages of esters and a decrease in those of alcohols with the drop of fermentation temperature were reported. The activation energy (E(a)) was lower (approximately 36%) and the reaction rate constant (k) was higher (approximately 78% at 30 degrees C and approximately 265% at 15 degrees C) in the case of immobilized cells compared to free cells, especially at low temperatures. These results show that corn starch gel may act as a promoter for the enzymes that are involved in the process or as a catalyst of the alcoholic fermentation and can explain the capability of immobilized cells for extremely low-temperature winemaking. Therefore, these results open a new way for research to find new catalysts in biotechnological processes.
authors.affiliation: Food Biotechnology Group, Department of Chemistry, University of Patras, GR-26500 Patras, Greece.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Kandylis
authors.forename: Amalia
authors.initials: A
authors.lastname: Goula
authors.forename: Athanasios A
authors.initials: AA
authors.lastname: Koutinas
mesh_terms: D002384:Catalysis; D018914:Cells, Immobilized / Q000737:chemistry / Q000378:metabolism*; D004952:Esters / Q000032:analysis; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D007700:Kinetics; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism*; D013213:Starch / Q000737:chemistry; D014835:Volatilization; D014920:Wine / Q000032:analysis*; D003313:Zea mays / Q000737:chemistry
chemical_list: D004952:Esters; D000431:Ethanol; D013213:Starch