ABSTRACT
Several factors are creating increased interest in the production of fuels and chemicals via bioconversion. Bioconversion provides a route to organic chemicals and fuels that does not depend on petroleum feedstocks. Increasing petroleum prices have occurred in the past and are anticipated in the future; the supplies of petroleum are decreasing and disruptions to supplies can occur anytime. Biocon version provides a new potential market for grain products. The environmental effects of bioconversion are relatively benign by comparison to synthetic (petroleum-based) chemical conversion (Busche, 1989; Young, 1989). The pro duction of fuels and chemicals from biomass via bioconversion could decrease the net production of greenhouse gases. In addition, bioconversion provides an alternative method for disposing of wastes; many industrial wastes are suitable feedstocks for bioconversion. Recent developments in molecular biology and in separations technology have also increased the potential of bioconversion for the production of fuels and chemicals. The pertinent issues on this topic have been described and evaluated by Leeper and Andrews (1991) and Leeper et al. (1991). However, product recovery costs remain a major barrier to increased use of bioconversion for the production of fuels and chemicals. Advances in separation technology are vital to the successful development of a bioconversion-based fuels and chemicals industry. Most organic chemical products of bioconversion are produced in low concentration in water. Recovery of these products is energy
intensive and expensive. The integration of membrane technology separations into product recovery processing may reduce the energy requirements and costs of product recovery in bioconversion. In this vein, the status of membrane technology for the recovery of fuels and organic chemicals produced via bioconversion is reviewed. This review is an update of a previous review on the subject of membrane separations in the production of alcohol fuels (Leeper, 1986). In this chapter, data and literature published since the previous review are compiled and discussed. Products that are discussed in this review include ethanol, acetone, butanol, isopropanol, and other organic fuels/chemicals produced by fermentation. Separa tion technologies that are discussed include pervaporation (PV), vapor permeation (VPe), reverse osmosis (RO), membrane extraction (perstraction), and electro dialysis (ED). Ultrafilatration (UF) is not discussed in this chapter. The literature on UF in biotechnology is expansive. In addition, the primary uses of UF in biotechnology involve concentration of cells, clarification of fermentation broth, and retention of cells in membrane bioreactors. UF applications in biotechnology are discussed by Strathmann (1985), Klinkowski (1983), Michaels and Matson (1985), Cheryan (1986), and Eykamp and Steen (1987). This chapter is limited to uses of membrane separation operations that directly increase the purity of fuels and organic chemicals produced by fermentation.
