Production, characterization and application of a thermostable polygalacturonase of a thermophilic mould Sporotrichum thermophile Apinis

摘要

The production of polygalacturonase (PGase) by Sporotrichum thermophile Apinis in stirred submerged fermentation (SmF) was high in comparison with that in static conditions. Yeast extract (0.25%) and citrus pectin (2%) at pH 7.0 and 45 degreesC supported a high enzyme production in flasks agitated at 200 rpm. An over-all 1.75-fold enhancement in PGase production was achieved as a result of optimization. The enzyme was optimally active at pH 7.0 and 55 degreesC, and exhibited t(1/2) of 4 h at 65 degreesC. The K-m and V-max values of the enzyme (for pectin) were 0.416 mg ml(-1) and 0.52 mumol mg(-1) min(-1), respectively. The PGase activity was stimulated by Mn2+ and Fe2+, but inhibited strongly by Mg2+, and slightly by Tween 80 and Triton X-100. Among the additives tested, beta-mercaptoethanol exerted a strong inhibitory effect, suggesting a critical role of disulphide linkages in maintaining a suitable conformation of the enzyme. An increase in the yield of banana, grape and apple juices was recorded due to the treatment of fruit pulps with the mixture of enzymes (pectinase, xylanases and cellulase) of S. thermophile as compared to that with only pectinase. The yield of fruit juices did not increase with enhanced titre of cellulase in the enzyme mixture. (C) 2004 Elsevier Ltd. All rights reserved.