Kandylis Panagiotis, Goula Amalia, Koutinas Athanasios A
Food Biotechnology Group, Department of Chemistry, University of Patras, GR-26500 Patras, Greece.
J Agric Food Chem. 2008 Dec 24;56(24):12037-45. doi: 10.1021/jf802476w.
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.
通过将酿酒酵母AXAZ-1酵母细胞固定在玉米淀粉凝胶基质中制备了一种新型生物催化剂。该生物催化剂用于在各种糖浓度（110-280 g/L）下对葡萄糖和葡萄汁进行重复分批发酵以及低温酿酒（5℃）。该生物催化剂在很长一段时间内保持其操作稳定性，并且被证明能够生产干型和半甜型葡萄酒。通过气相色谱（GC）和气相色谱-质谱联用（GC-MS）对所生产葡萄酒的挥发性副产物进行了分析，结果表明固定化细胞产生的酯类数量和含量有所增加。此外，据报道随着发酵温度的降低，酯类的百分比增加而醇类的百分比降低。与游离细胞相比，固定化细胞的活化能（E(a)）较低（约36%），反应速率常数（k）较高（在30℃时约高78%，在15℃时约高265%），尤其是在低温下。这些结果表明玉米淀粉凝胶可能作为该过程中所涉及酶的促进剂或酒精发酵的催化剂，并且可以解释固定化细胞进行极低温酿酒的能力。因此，这些结果为在生物技术过程中寻找新催化剂的研究开辟了一条新途径。
