Pearson Carrie R, Heng Meng, Gebert Mark, Glatz Charles E
Department of Chemical Engineering, Iowa State University, Ames, IA 50011, USA.
Biotechnol Bioeng. 2004 Jul 5;87(1):61-8. doi: 10.1002/bit.20098.
Association of extracellular protein product with flocculated cells reduces product yield. Here, partitioning of the enzyme subtilisin between the liquid and polyelectrolyte-flocculated and sedimented Bacillus increased as the polymer dosage was increased beyond that necessary to obtain optimum floc character (brain floc) for cell removal by centrifugation. Partitioning to the cell floc is partly physical entrapment at all polymer dosages; however, at higher levels there is also direct interaction between the polyelectrolyte and enzyme. Enzyme loss was not likely due to pH denaturation during the flocculation process because conditions were within the stable pH range of the enzyme. The direct interaction between polyelectrolyte and enzyme was characterized through turbidimetric titrations and partitioning studies. Neither changes in the polymer feed concentration nor the method of polymer addition reduced the enzyme loss at dosages optimal for cell removal.
细胞外蛋白质产物与絮凝细胞的结合会降低产物产量。在此，随着聚合物用量增加至超过通过离心去除细胞所需的最佳絮凝特性（脑絮凝）所需用量时，酶枯草杆菌蛋白酶在液体与聚电解质絮凝及沉淀的芽孢杆菌之间的分配增加。在所有聚合物用量下，酶向细胞絮凝物的分配部分是物理截留；然而，在较高用量时，聚电解质与酶之间也存在直接相互作用。酶损失不太可能是由于絮凝过程中的pH变性，因为条件处于酶的稳定pH范围内。通过比浊滴定和分配研究对聚电解质与酶之间的直接相互作用进行了表征。在用于细胞去除的最佳用量下，聚合物进料浓度的变化或聚合物添加方法均未降低酶损失。
