Immobilization of invertase in calcium alginate and calcium alginate-kappa-carrageenan beads and its application in bioethanol production

Invertase from Saccharomyces cerevisiae was entrapped in Ca-alginate and Ca-alginate-kappa-carrageenan matrix. Optimum pH for the free and immobilized invertase was found to be 4.5 and 5.5, respectively. The optimum hydrolysis temperature was 55 degrees C for both the free and immobilized forms. K-m values for free invertase and invertase entrapped in Ca-alginate and Ca-alginate-kappa-carrageenan beads were 15, 21, and 19 mM, respectively. Values of V-max for free invertase and invertase entrapped in Ca-alginate and Ca-alginate-kappa-carrageenan beads were 238, 186, and 197 mM min(-1), respectively. Invertase entrapped in Ca-alginate-kappa-carrageenan matrix had the highest pH and thermal stability, higher reusability with 71% retention in activity after nine batches of reuse and higher storage stability with 86% activity retention after 12 weeks at 4 degrees C, pH 4.5. Fermentation of cane molasses by yeast for bioethanol formation in the presence of free invertase at 30 degrees C, pH 5.0, led to an increase in ethanol production by 3%. However, the production increased by 9% when invertase entrapped in Ca-alginate-kappa-carrageenan was used as a catalyst.