CLEAs aggregates

Immobilized enzymes, particularly LAC, have been employed in the degradation of triclosan. The immobilization of LAC from Coriolopsis polyzona through the formation of cross-linked enzyme aggregates (CLEAs) and their subsequent use in an FBR for the removal of endocrine disrupting compounds [42] produced the complete removal of triclosan, nonylphenol, and bisphenol A (5 mg L-1 each) at a HRT of 150 min. The application of CLEAs in a perfusion basket reactor [43]... 

Effective and simple immobilization of enzymes can be obtained by the cross-linking of enzyme aggregates, so-called CLEAs [55]. In this way, essentially any enzyme, including crude preparations, can be transformed into a heterogeneous type of material, insoluble in both water and organic solvents, that is stable and recyclable with high retention of the enzyme s original activity [56], These enzyme preparations are, therefore, of special value for both bio-bio and bio-chemo cascade processes. 

The 3-pyridinecarboxyaldehyde 58 is highly water soluble, and so the spontaneous cyanide addition to give racemic cyanohydrin cannot be suppressed unless the aqueous pH is lowered below 3.5, which is not tolerated by the enzymes. The only available option is to operate in a 100% organic solvent system. This was recently made possible by the availability of the cross linked enzyme aggregate particles (CLEAs), which can tolerate organic solvents [64]. The individual precipitated protein molecules are chemically bonded to one another through the formation... 

The commercially available CLEA particles of hydroxynitrile lyases (HNLs) from cassava and almond were used to produce both enantiomers. The use of dichloromethane, free hydrogen cyanide, and low temperatures was important for improving the cyanohydrin stereoselectivity and suppressing the background reaction. The aggregate particles were easily separated from the reaction by filtration followed by washing, and up to ten times reuse was demonstrated. 

The cross-linked aggregates of MeHNL also showed themselves to be highly active and robust catalysts. Optimized procedures give MeHNL CLEAs with activity recoveries up to 93% measured by a synthetic assay [75]. As observed earlier for PaHNL CLEAs [74], this result is in contrast with the photometric assay, indicating that a fast assay severely underestimates the recovery of initial activity because of rate-limiting diffusion [75]. 

The conversion of benzaldehyde by the encapsulated HNLs afforded mandelo-nitrile in 96-98% yield and 97-99% for all three enzymes. Free and entrapped HfoHNL catalyzed the conversion of hexanal with 94% , whereas ee-values of only 85 and 87% could be achieved with MeHNL and PaHNL preparations, respectively, limited by the intrinsic enantioselectivity of the enzymes (Table 9.4). Furthermore, the CLEAs from HfoHNL and PaHNL suffered from activity loss under the reaction conditions in contrast to MeHNL CLEA, indicating that the cross-linked aggregates from MeHNL are particularly robust and necessitate only traces of water to keep the catalytic activity [87]. 

Sheldon, R.A., Sorgedrager, M.J. and Janssen, M.H.A. (2007) Use of cross-linked enzyme aggregates (CLEAs) for performing biotransformations. Chim. Oggi — Chemistry Today, 25, 62. 

Cross-linked CPO aggregates in the pores of mesocellular foams The CPO-CLEAs (cross-linked enzyme aggregates) supported in mesocellular foams were more stable against leaching than conventional catalysts prepared by physical adsorption of CPO on the same support [10]... 

Immobilization of Enzymes Cross-linked Enzyme Aggregates (CLEAs) 405... 

Cross-hnked enzyme aggregates (CLEA) are prepared by first aggregating enzymes via the addition of predpitants such as ammonium sulfate, acetone. 

Schoevaait R, Wolbers MW, Golubovic M et al. (2004) Preparation, optimization and structures of cross-linked enzyme aggregates (CLEAs). Biotechnol Bioeng 87 754-762 Schuleit M, Luisi PL (2001) Enzyme immobDization in silica-hardened organogels. Biotechnol... 

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