Membrane technology and biotechnology

Abstract

The rapidly growing field of biotechnology, which now encompasses sophisticated fermentation processes utilizing normal and genetically altered microorganisms, biochemical conversions employing immobilized enzymes and cells, and the production of biological products from mammalian cell cultures, is demanding increasingly more efficient and economic means of culturing microorganisms, of recovering and isolating costly labile products, and of disposing of objectionable toxic wastes. Membrane and membrane-separation technology is finding increasing attention today as a means for solving these problems. Continuous crossflow filtration with microporous or ultrafiltration membranes is now being used to separate cells from supernatant in whole fermentation broths with high product recovery, and elimination of a major waste-disposal problem. Reverse osmosis and ultrafiltration are receiving increased attention as a means for concentrating fermentation liquors to facilitate final product recovery, or for demineralizing or removing colloidal impurities from product-containing solutions to improve product yield and purity. Hollow-fiber membrane devices have been found to serve as excellent “artificial capillary beds” for the maintenance of mammalian cell cultures; such devices are now being used as artificial organs, and for the production of hormones, viruses, vaccines, and antibodies for diagnostic and therapeutic uses. Recently, hollow-membrane fibers have been shown to be attractive media for the growth and support of microbial (bacteria, yeast, etc.) populations at very high cell densities (10 12/cm 3), and may provide the basis for a new family of high-capacity, continuous-production bioreactors. Immobilized enzyme reactors, which employ membranes as matrices for enzyme containment, are now gaining increasing popularity for the conduct of continuous biochemical transformations. In addition, enzyme-containing membranes are showing considerable promise in the development of novel electrochemical and thermo-chemical sensors for detection and measurement of complex biochemical substances; such sensors are expected to play an important role in the design of control instrumentation for biochemical manufacturing processes.