生物反应工程教学课件-Assignment-I.pdfVIP

Problems for Chapter 2 2.1. Cell concentration using membranes A battery of cylindrical hollow-fibre membranes is operated at steady state to concentrate E. coli suspension from a fermenter. 350 kg min1 fermented broth is pumped through a stack of hollow-fibre membranes as shown in Figure P2.1. The broth contains 1% E. coli ; the rest may be considered as water. Buffer solution enters the annular space around the membrane tubes at a rate of 80 kg min1; because the broth in the membrane tubes is under pressure, water is forced across the membrane into the buffer. E. Coli Cells in the broth are too large to pass through the membrane poles and pass out of the tubes as a concentrated product. The aim of this system is to produce a E. coli suspension containing 6% biomass. Figure P2.1 Hollow-fibre membrane for concentration of E. coli fermented broth Fermentation broth Hollow-fibre membrane Buffer solution (a) What is the flow rate from the annular space? (b)What is the flow rate of E. coli cell suspension from the membrane tubes? Assume that the cells are not active, i.e. they do not grow. Also assume that the membrane does not allow any molecules other than water to pass from annulus to inner cylinder, or vice versa. 2.2. Membrane bioreactor A battery of cylindrical membranes similar to that shown in Figure P2.1 is used for an extractive bioconversion. Extractive bioconversion means that fermentation and extraction of product occur at the same time. Yeast cells are immobilized within the membrane walls. A 10% glucose in water solution is passed through the annular space at a rate of 40 kg h1. An organic solvent, such as 2-ethyl-1,3-hexanediol, also enters the inner tube at a rate of 40 kg h1. Because the membrane is constructed o