Enzyme-enhanced solvent extraction

Fullbrook (1983) used proteolytic enzymes and carbohydrases to enhance oil recovery of finely milled slurries of melon seeds, soybeans and rapeseeds. Better yields of oil recoveries were obtained when hexane was added to the aqueous slurries, however, the amounts were significantly lower than the Soxhlet extractable oils in the samples. 

Studies conducted by Sosulski et al, (1988) on canola show that enzyme treatment of canola flakes could improve oil recovery by 4.0% and 7.7% 

The major drawback of this process is the long incubation periods needed for optimum oil recovery. The additional cost of enzymes on top of solvent cost could also be of concern although it is possible that solvent usage could be drastically reduced for enzyme treated materials. The quality characteristics of the extracted oil and the meal may, on the other hand, be important factors in considering this process for industrial use. 

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Conventional methods for extracting oils involve three basic approaches physical, chemical and a combination of both. In all cases the fundamental mechanism is to rupture the cell structure of the oil-bearing plant or animal materials and subsequently or simultaneously remove the oil. Enzymes have found use in oil extraction and their applications can be categorized as enzymes that assist pressing, enzymes that enhance solvent extraction and enzymes that assist aqueous extraction. 

The first step for the design of an EMR is to select the type of reactor. Extractive membrane reactors are desirable when one of the substrates or products is poorly soluble in aqueous solution or when an undesirable by-product has to be separated, as the membrane acts as a solvent extraction step [99]. Immobilized enzyme reactors are usually applied with materials that enable enhancement of enzymatic stability or preserve enzyme from deactivation by a direct contact with an organic solvent [99]. Finally, direct-contact membrane reactors are the most versatile alternative in processes with soluble compounds. 

The solvent extraction can be enhanced by utilizing carbohydrate-hydrolyzing enzymes, for instance pectinase, cellulase, hemicellulase, and many other enzymes, which can be used to disintegrate the plant cell-wall matrix leading to more efficient release of phenolic compounds [36]. Enzymatic-assisted extraction has been applied for superior extraction of pol3q)henolic compounds from different biomaterials, such as black currant juice press residues [37, 38], pigeon pea leaves [39], and grape pomace [40]. 

Tween 85 is used extensively for RME [84]. Russell and coworkers [234] used Tween 85/isopropanol microemulsions in hexane to solubilize proteins and not only showed >80% solubilization of cytochrome C at optimum conditions, but also proved that Tween 85 does not have a detrimental effect on the structure, function, and stability of subtilisin and cytochrome C. There are other reports available on the extraction and purification of proteins using Tween 85-RMs and also on the stability of protein activity in these systems [234]. It has also been shown that Tween 85-RMs can solubilize larger amounts of protein and water than AOT. Tween 85 has an HLB of 11, which indicates that it is soluble in organic solvents. In addition, it is biodegradable and can be successfully used as an additive in fertihzers [235,236]. Pfammatter et al. [35] have demonstrated that RMs made of Tween 85 and Span 80 can be successfully used for the solubilization and growth of whole cells. Recently, Hossain et al. [84] showed an enhanced enzymatic activity of Chromobacterium viscosum Hpase in AOT/Tween 85 mixed reverse micellar systems when compared to that in classical AOT-RMs. This is due to the modification of the interface in AOT-RMs caused by the co-adsorption of Tween 85, and increased availability of the oHve oil molecules (substrate) to the enzyme. 

Surface enhanced laser desorption/ionization (SE-LDI) is a variant of MALDI in which the MALDI probe is derivatized with various substances that have affinity for the analyte. The probes are then used to extract the analyte directly from mixtures thus avoiding sample loss through more complicated procedures such as column chromatography. Contaminants can be washed from the probe with appropriate buffers or solvents leaving the purified analyte ready for analysis. Many adsorbents have been used typical examples are hydrophobic or ionic compounds, enzymes, various receptors, antibodies, and nucleic acids. Although most applications have been reported with proteins, the technique is potentially applicable to any type of compound for which a specific adsorbent can be attached to the probe. 

Attempts to enhance the low stability by supporting the enzyme on low melting agar has been carried out successfully [51]. Supercritical carbon dioxide was also used as solvent/reagent for semi-purified phenylphosphate carboxylase extracted from T. aromatica [52]. 

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