Juhász Tamás, Egyházi Anita, Réczey Kati
Department of Agricultural Chemical Technology, Budapest University of Technology and Economics, Szent Gellért tér 4, Budapest, 1521 Hungary.
Appl Biochem Biotechnol. 2005 Spring;121-124:243-54.
The hydrolysis of cellulose to the water-soluble products cellobiose and glucose is achieved via synergistic action of cellulolytic proteins. The three types of enzymes involved in this process are endoglucanases, cellobiohydrolases, and beta-glucosidases. One of the best fungal cellulase producers is Trichoderma reesei RUT C30. However, the amount of beta-glucosidases secreted by this fungus is insufficient for effective cellulose conversion. We investigated the production of cellulases and beta-glucosidases in shake-flask cultures by applying three pH-controlling strategies: the pH of the production medium was adjusted to 5.8 after the addition of seed culture with no additional pH adjustment performed, the pH was adjusted to 6.0 daily, and the pH was maintained at 6.0 by the addition of Tris-maleate buffer to the growth medium. Different carbon sources Solka Floc 200, glucose, lactose, and sorbitol were added to standard Mandels nutrients. The lowest beta-glucosidase activities were obtained when no pH adjustment was done regardless of the carbon source employed. Somewhat higher levels of beta- glucosidase were measured in the culture filtrates when daily pH adjustment was carried out. The effect of buffering the culture medium on beta-glucosidase liberation was most prominent when a carbon source inducing the production of other cellulases was applied.
纤维素通过纤维素分解蛋白的协同作用水解为水溶性产物纤维二糖和葡萄糖。参与此过程的三种酶是内切葡聚糖酶、纤维二糖水解酶和β-葡萄糖苷酶。里氏木霉RUT C30是最佳的真菌纤维素酶产生菌之一。然而，该真菌分泌的β-葡萄糖苷酶量不足以实现有效的纤维素转化。我们通过应用三种pH控制策略，研究了摇瓶培养中纤维素酶和β-葡萄糖苷酶的产生：在添加种子培养物后将生产培养基的pH值调至5.8，之后不再进行额外的pH调节；每天将pH值调至6.0；通过向生长培养基中添加马来酸三羟甲基氨基甲烷缓冲液将pH值维持在6.0。在标准曼德尔营养素中添加了不同的碳源，即Solka Floc 200、葡萄糖、乳糖和山梨醇。无论使用何种碳源，不进行pH调节时获得的β-葡萄糖苷酶活性最低。每天进行pH调节时，在培养滤液中测得的β-葡萄糖苷酶水平略高。当使用诱导产生其他纤维素酶的碳源时，缓冲培养基对β-葡萄糖苷酶释放的影响最为显著。
