Although many methods for enzyme immobilization have been described in patents and publications, relatively few processes employing immobilized enzymes have been successfully commercialized. The cost of most industrial enzymes is often only a minor component in overall process economics, and in these instances, the additional costs associated with enzyme immobilization are often not justified. More commonly the benefit realized from enzyme immobilization relates to the process advantages that an immobilized catalyst offers, for example, enabling continuous production, improved stability and the absence of the biocatalyst in the product stream. The development and attributes of several established and emerging industrial applications for immobilized enzymes, including high-fructose corn syrup production, pectin hydrolysis, debittering of fruit juices, interesterification of food fats and oils, biodiesel production, and carbon dioxide capture are reviewed herein, highlighting factors that define the advantages of enzyme immobilization.

Suberin from the roots of carrots (Daucus carota), parsnip (Pastinaca sativa), rutabaga (Brassica napobrassica), turnip (Brassica rapa), red beet (Beta vulgaris), and sweet potato (Ipomoea batatas) was isolated by a combination of chemical and enzvmatic techniques. Finely powdered suberin was depolymerized with 14% BFs in methanol, and soluble monomers (20-50% of suberin) were fractionated into phenolic (< 10 % ) and aliphatic (13-35%) fractions. The aliphatic fractions consisted mainly of w-hydroxyacids (29-43%), dicarboxylic acids (16-27%), fatty acids (4-18%), and fatty alcohols (3-6%). Each fraction was subjected to combined gas-liquid chromatography and mass spectrometry. Among the fatty acids very long chain acids (>C2o) were the dominant components in all six plants. In the alcohol fraction C18, C20, C2, and C24 saturated primary alcohols were the major components. C16 and Ci8 dicarboxylic acids were the major dicarboxylic acids of the suberin of all six plants and in all cases octadec-9-ene-1,18-dioic acid was the major component except in rutabaga where hexadecane-1 ,16-dioic acid was the major dicarboxylic acid. The composition of the w-hydroxyacid fraction was quite similar to that of the dicarboxylic acids; 18-hydroxy-octadec-9-enoic acid was the major component in all plants except rutabaga, where equal quantities of 16-hydroxyhexadecanoic acid and 18-hydroxvoctadec-9-enoic acid (42% each) were found. Compounds which would be derived from 18-hydroxyoctadec-9-enoic acid and octadec-9-ene-1, 18-dioic acid by epoxidation, and epoxidation followed by hydration of the epoxide, were also detected in most of the suberin samples. The monomer composition of the six plants showed general similarities but quite clear taxonomic differences.A polymeric material derived from lipids constitutes the structural component of the outer layer of plants, whereas pro-

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Enzymatic reactions with surface-bound substrates present an interesting problem in biomolecular surface science, as they require us to consider traditional enzyme kinetics in the context of protein adsorption. These reactions are important in such applications as detergent enzyme additives, food processing, and contact lens cleaning. We study the interaction of a serine protease (subtilisin) with an immobilized substrate (bovine serum albumin) surface through the simultaneous use of surface plasmon resonance and surface plasmon enhanced fluorescence techniques. We measure adsorbed enzyme concentrations and substrate cleavage rates in situ and compare the reactivities with those in solution. By varying the ionic strength of the reaction environment and studying several single point mutations of subtilisin, we find the adsorption behavior of the enzyme is strongly influenced by its electrostatic interactions with the charged bovine serum albumin surface. The surface reactivity of each of the mutants is coupled to its adsorption properties. On the basis of these findings, we propose a modified Michaelis-Menten enzyme surface adsorption and reaction model.

We describe an optical technique for the measurement of macromolecular adsorption at the solid/liquid interface when multiple species are present. The technique combines surface plasmon resonance (SPR) with simultaneous surface plasmon enhanced fluorescence (SPEF). The relative ease of construction and linear correlation between SPR and SPEF signals make the technique amenable for coadsorption studies or multiple ligand binding experiments. Here, we demonstrate the utility of the technique with a biotin/ avidin/BSA "sandwich" experiment. We then apply SPR/SPEF for the simultaneous monitoring of enzyme adsorption and substrate cleavage of a protease interacting with a substrate surface.