A continuous membrane bioreactor for ester synthesis in organic media: I. Operational characterization and stability

The feasibility of continuous ester synthesis in a membrane bioreactor (MBR ) by a recombinant cutinase from Fusarium solani pisi was investigated, usi ng the optimal conditions previously attained by medium engineering. The objective was to analyze the MBR behavior as a differential or an integ ral reactor. The main component of the reactor was an anisotropic ceramic m embrane with 15,000 NMWCO. The operating variables included the influence o f substrates ratio and flow rate on the conversion degree and on the produc tivity. The highest conversion degree was obtained using 1M of hexanol and 0.1M of butyl acetate as acyl donor. The use of these substrate concentrati ons led to a conversion degree of 79.3% and a specific productivity of 41 g hexyl acetate/(d . g cutinase), when the permeate flow rate was 0.025 mL/m in. The increase of flow rate to 0.4 mL/min decreased the conversion to 35. 6% although, the productivity was enhanced to 294 g product/day g enzyme. The MBR characterization involved the calculations of mass balance, recircu lation rate, conversion per pass, number of cycles, and hydraulic residence time. The operational stability was also evaluated in a longterm experiment over 900 hours and the enzyme half-life was estimated to be approximately 2 year s. (C) 2000 John Wiley & Sons, Inc.