Obtaining monoglycerides by esterification of glycerol with palmitic acid using some high activity preparations of Candida antarctica lipase B

Enzyme-Coated Micro-Crystals: An Almost Forgotten but Very Simple and Elegant Immobilization Strategy

The immobilization of enzymes using protein coated micro-crystals (PCMCs) was reported for the first time in 2001 by Kreiner and coworkers. The strategy is very simple. First, an enzyme solution must be prepared in a concentrated solution of one compound (salt, sugar, amino acid) very soluble in water and poorly soluble in a water-soluble solvent. Then, the enzyme solution is added dropwise to the water soluble solvent under rapid stirring. The components accompanying the enzyme are called the crystal growing agents, the solvent being the dehydrating agent. This strategy permits the rapid dehydration of the enzyme solution drops, resulting in a crystallization of the crystal formation agent, and the enzyme is deposited on this crystal surface. The reaction medium where these biocatalysts can be used is marked by the solubility of the PCMC components, and usually these biocatalysts may be employed in water soluble organic solvents with a maximum of 20% water. The evolution of these PCMC was to chemically crosslink them and further improve their stabilities. Moreover, the PCMC strategy has been used to coimmobilize enzymes or enzymes and cofactors. The immobilization may permit the use of buffers as crystal growth agents, enabling control of the reaction pH in the enzyme environments. Usually, the PCMC biocatalysts are very stable and more active than other biocatalysts of the same enzyme. However, this simple (at least at laboratory scale) immobilization strategy is underutilized even when the publications using it systematically presented a better performance of them in organic solvents than that of many other immobilized biocatalysts. In fact, many possibilities and studies using this technique are lacking. This review tried to outline the possibilities of this useful immobilization strategy.

Protein-Coated Microcrystals, Combi-Protein-Coated Microcrystals, and Cross-Linked Protein-Coated Microcrystals of Enzymes for Use in Low-Water Media

Protein-coated microcrystals (PCMC) are a high-activity preparation of enzymes for use in low-water media. The protocols for the preparation of PCMCs of Subtilisin Carlsberg and Candida antarctica lipase B (CAL B) are described. The combi-PCMC concept is useful both for cascade and non-cascade reactions. It can also be beneficial to combine two different specificities of a lipase when the substrate requires it. Combi-PCMC of CALB and Palatase used for the conversion of coffee oil present in spent coffee grounds to biodiesel is described. Cross-linked protein-coated microcrystals (CL-PCMC) in some cases can give better results than PCMC. Protocols for the CLPCMC of Subtilisin Carlsberg and Candida antarctica lipase B (CAL B) are described. A discussion of their applications is also provided.

Oleochemical industry future through biotechnology

Lipases are the most widely used class of enzymes in organic synthesis. Enzymatic processes have been implemented in a broad range of industries as they are specific, save raw materials, energy and chemicals, environmentally friendly and fast in action compared to conventional processes. The most notable benefit is the moderate process temperature and pressure with no unwanted side reactions. In the past two decades, intensive research was carried out towards enzymatic synthesis of oleochemicals. This review has a sharp focus on the current implemented enzymatic processes for producing different oleochemicals such as fatty acids, glycerin, biodiesel, biolubricant and different alkyl esters via different processes including hydrolysis, esterification, transesterification and intraesterification.

High activity preparations of lipases and proteases for catalysis in low water containing organic solvents and ionic liquids

Simple precipitation of enzymes has shown impressive catalytic efficiencies in organic solvents. In asmuch as these can be recovered after the reaction, these can be viewed as immobilized preparations just like more extensively used cross-linked enzyme aggregates (CLEAs). This chapter describes three protocols which use these enzyme precipitated and rinsed with propanol/some other appropriate organic solvent. The first two protocols show their applications in ionic liquids for a transesterification reaction and a kinetic resolution. The third protocol presumably incorporates an "imprinting" effect so that the precipitates are now able to efficiently catalyze transesterification of tributyrin with tertiary alcohols.

Alpha chymotrypsin coated clusters of Fe3O4 nanoparticles for biocatalysis in low water media

Background

Enzymes in low water containing non aqueous media are useful for organic synthesis. For example, hydrolases in such media can be used for synthetic purposes. Initial work in this area was carried out with lyophilized powders of enzymes. These were found to have poor activity. Drying (removing bulk water) by precipitation turned out to be a better approach. As enzymes in such media are heterogeneous catalysts, spreading these precipitates over a large surface gave even better results. In this context, nanoparticles with their better surface to volume ratio provide obvious advantage. Magnetic nanoparticles have an added advantage of easy separation after the reaction. Keeping this in view, alpha chymotrypsin solution in water was precipitated over a stirred population of Fe₃O₄ nanoparticles in n-propanol. This led to alpha chymotrypsin activity coated over clusters of Fe₃O₄ nanoparticles. These preparations were found to have quite high transesterification activity in low water containing n-octane.

Results

Precipitation of alpha chymotrypsin over a stirred suspension of Fe₃O₄ nanoparticles (3.6 nm diameter) led to the formation of enzyme coated clusters of nanoparticles (ECCNs). These clusters were also magnetic and their hydrodynamic diameter ranged from 1.2- 2.6 microns (as measured by dynamic light scattering). Transmission electron microscopy (TEM), showed that these clusters had highly irregular shapes. Transesterification assay of various clusters in anhydrous n-octane led to optimization of concentration of nanoparticles in suspension during precipitation. Optimized design of enzyme coated magnetic clusters of nanoparticles (ECCN 3) showed the highest initial rate of 465 nmol min^-1 mg^-1protein which was about 9 times higher as compared to the simple precipitates with an initial rate of 52 nmol min^-1 mg^-1 protein.

Circular Dichroism (CD)(with a spinning cell accessory) showed that secondary structure content of the alpha Chymotrypsin in ECCN 3 [15% α-helix, 37% β-sheet and 48% random coil] was identical to the simple precipitates of alpha chymotrypsin.

Conclusion

A strategy for obtaining a high activity preparation of alpha chymotrypsin for application in low water media is described. Such high activity biocatalysts are useful in organic synthesis.