Pedrolli Danielle Biscaro, Gomes Eleni, Monti Rubens, Carmona Eleonora Cano
Departamento de Bioquímica e Microbiologia, Instituto de Biociências, Universidade Estadual Paulista - Unesp., Av. 24A, 1515, CEP 13506-900, Rio Claro, SP, Brazil.
Appl Biochem Biotechnol. 2008 Feb;144(2):191-200. doi: 10.1007/s12010-007-8059-1.
Polygalacturonases are part of the group of enzymes involved in pectin degradation. The aim of this work was to investigate some of the factors affecting polygalacturonase production by an Aspergillus giganteus strain and to characterize this pectinolytic activity. Several carbon sources, both pure substances and natural substrates, were tested in standing cultures, and the best results were obtained with orange bagasse and purified citrus pectin. On citrus pectin as sole carbon source, the highest extracellular activity (9.5 U/ml and 40.6 U/mg protein) was obtained in 4.5-day-old cultures shaken at 120 rpm, pH 3.5 and 30 degrees C, while on orange bagasse, the highest extracellular activity (48.5 U/ml and 78.3 U/mg protein) was obtained in 3.5-day-old cultures shaken at 120 rpm, pH 6.0 and 30 degrees C. Optimal polygalacturonase activity was observed in assays conducted at pH 5.5-6.5 and 55-60 degrees C. The activity showed good thermal stability, with half-lives of 90 and 30 min when incubated at 55 and 60 degrees C, respectively. High stability was observed from pH 4.5 to 8.5; more than 90% of the activity remained after 24 h in this pH range.
多聚半乳糖醛酸酶是参与果胶降解的酶类中的一部分。本研究的目的是探究影响巨大曲霉菌株产生多聚半乳糖醛酸酶的一些因素，并对这种果胶分解活性进行表征。在静置培养中测试了几种碳源，包括纯物质和天然底物，结果发现橙皮渣和纯化的柑橘果胶效果最佳。以柑橘果胶作为唯一碳源时，在4.5日龄、120 rpm振荡培养、pH 3.5和30℃条件下培养的菌株，胞外活性最高（9.5 U/ml和40.6 U/mg蛋白质）；而以橙皮渣为碳源时，在3.5日龄、120 rpm振荡培养、pH 6.0和30℃条件下培养的菌株，胞外活性最高（48.5 U/ml和78.3 U/mg蛋白质）。在pH 5.5 - 6.5和55 - 60℃条件下进行的测定中观察到多聚半乳糖醛酸酶的最佳活性。该活性表现出良好的热稳定性，在55℃和60℃下孵育时，半衰期分别为90分钟和30分钟。在pH 4.5至8.5范围内观察到高稳定性；在此pH范围内24小时后仍保留超过90%的活性。
