Production of cocktail enzymes and partial purified pectinase utilizing lignocellulosic wastes by specific Didymella species

Abstract

Three possible novel Didymella species, isolated from Mango and Guava juices in Assiut, Egypt, were identified based on morphology and sequencing of the internal transcribed spacers region (ITS). The three strains could ferment five lignocellulosic residues, namely bean straw, corn cobs, rice husk, wheat bran, and wheat straw in solid-state fermentation (SSF) and produce cocktail enzymes (endoglucanase, exoglucanase, laccase, pectinase, and xylanase). Didymella sp. AUMC 15636 and AUMC 15637 produced the most endoglucanase, exoglucanase and xylanase activity (20 and 23, 10 and 17, 18 and 18 U/gds, respectively) on bean straw, and laccase (0.7 and 2.6 U/gds) on corn cobs and wheat bran, in addition to pectinase (37 and 26 U/gds) on rice husk and corn cobs, respectively. Didymella sp. AUMC 15640 released the maximum endoglucanase, exoglucanase, laccase, pectinase, and xylanase enzymes on the bean straw residues (24, 24, 10, 31 and 27 U/gds), respectively. Didymella sp. AUMC 15636 yielded 0.9 g crude pectinase per liter fermentation medium in submerged fermentation (SmF). At pH 6.0, a peak in pectinase activity (80 U/gds) was detected, which rose to 100 U/gds at 45 ºC. Presence of Mn 2+ ions activated the pectinase by 30% over the control. Zn 2+ and EDTA had no effect on pectinase activity, while sodium dodecyl sulfate and other ions lowered pectinase activity by 10 to 30%, while K + and Ca 2+ having the highest impact. The target of this study, which is advocated here by utilizing such strains, is to