| Summary: | A filamentous fungus producing polygalacturonase (29.2 U/mL) was isolated from orchard soil in northern Guangxi, and identified as Trichoderma koningiopsis. Using polygalacturonic acid as the substrate, the optimum reaction temperature of the enzyme was 50 ℃, and it maintained more than 70% of the maximum activity at 50 ℃ for 1 h, which was identified as a medium-high temperature tolerant enzyme. The enzyme had unique weakly acidic catalytic characteristics. The optimum reaction pH was 5.0, and it retained 73% of its maximum activity at pH 6.0, and was tolerant to pH 2.5–8.0. Zn2+ partially activated the enzyme activity, while Mn2+ inhibited the enzyme. It could depectinize five weakly acid fruit pulps (papaya, banana, banana, and white- and red-fleshed pitaya) but to different extents. The yield of juice of banana pulp increased by 24.4%, the viscosity of papaya pulp decreased by 82.5%, and the transmittance of red-fleshed pitaya pulp increased by 31.9%, indicating good depectinization efficiency for the three fruits. The polygalacturonase-producing strain has good prospects for its application in juice production from tropical and subtropical perishable fruits.
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