Whittington P N, George N
Biological Treatment Division, Warren Spring Laboratory, Department of Trade and Industry, Stevenage, Hertfordshire, United Kingdom SG1 2BX.
Biotechnol Bioeng. 1992 Aug 5;40(4):451-8. doi: 10.1002/bit.260400402.
The optimization of microbial flocculation for subsequent biomass separation must relate the floc properties to separation process criteria. The effects of flocculant type, dose, and hydrodynamic conditions on floc formation in laminar tube flow were determined for an Escherichia coli system. Combined with an on-line aggregation sensor, this technique allows the flocculation process to be rapidly optimized. This is important, because interbatch variation in fermentation broth has consequences for flocculation control and subsequent downstream processing. Changing tube diameter and length while maintaining a constant flow rate allowed independent study of the effects of shear and time on the flocculation rate and floc characteristics. Tube flow at higher shear rates increased the rate and completeness of flocculation, but reduced the maximum floc size attained. The mechanism for this size limitation does not appear to be fracture or erosion of existing flocs. Rearrangement of particles within the flocs appears to be most likely. The Camp number predicted the extent of flocculation obtained in terms of the reduction in primary particle number, but not in terms of floc size.
为了实现后续生物质分离，微生物絮凝的优化必须将絮凝体特性与分离过程标准联系起来。对于大肠杆菌系统，测定了絮凝剂类型、剂量和流体动力学条件对层流管流中絮凝体形成的影响。结合在线聚集传感器，该技术可使絮凝过程迅速得到优化。这一点很重要，因为发酵液的批次间差异会对絮凝控制及后续下游加工产生影响。在保持流速恒定的情况下改变管径和管长，能够独立研究剪切力和时间对絮凝速率及絮凝体特性的影响。较高剪切速率下的管流提高了絮凝的速率和完整性，但减小了达到的最大絮凝体尺寸。这种尺寸限制的机制似乎并非现有絮凝体的破碎或侵蚀。絮凝体内颗粒的重新排列似乎是最有可能的原因。坎普数能够预测絮凝程度，即根据初级颗粒数量的减少来预测，但无法根据絮凝体尺寸进行预测。
