In the past couple of decades, cross linked enzyme aggregates (CLEAs) have emerged as a novel and versatile carrier free immobilization technique. The immobilization of enzymes as cross linked enzyme aggregates (CLEAs) involves precipitation of an enzyme from aqueous solution followed by cross linking with a bi-functional reagent. It is worth noting that many parameters alter the enzyme precipitation and the aggregate cross linking and hence affect the activity and stability of CLEAs. Therefore to endorse CLEAs for industrial application, each newly synthesised CLEA is characterized. This review intends to investigate the effects of various parameters, such as the nature and purity of the enzyme, the nature and amount of precipitant, the nature and amount of cross linker, the cross linking time, the pH and temperature during CLEA preparation and washing and separation techniques on the activity and stability of CLEAs. The major parameters such as catalytic properties, particle size and morphology, stability and reusability required for approval of industrial applicability of newly synthesized CLEAs are critically reviewed. Furthermore the scope of CLEAs in non-aqueous solvent, the development of one pot cascade processes and the design of different types of enzyme reactors is also discussed.

Parameters in preparation and characterization of cross linked enzyme aggregates (CLEAs)

Carrier free co-immobilization of alpha amylase, glucoamylase and pullulanase as combined cross-linked enzyme aggregates (combi-CLEAs): a tri-enzyme biocatalyst with one pot starch hydrolytic activity.

https://ro.uow.edu.au/cgi/viewcontent.cgi?article=7455&context=eispapers

Direct immobilization of laccase on titania nanoparticles from crude enzyme extracts of P. ostreatus culture for micro-pollutant degradation

Enzyme-based catalysis has become one of the most important disciplines in organic synthesis and plays a noteworthy role in the establishment of many chemical industries, e.g. fine chemical...

Modifying bio-catalytic properties of enzymes for efficient biocatalysis: a review from immobilization strategies viewpoint

Biocatalysis has emerged in the last decade as a pre-eminent technology for enabling the envisaged transition to a more sustainable bio-based economy. For industrial viability it is essential that enzymes can be readily recovered and recycled by immobilization as solid, recyclable catalysts. One method to achieve this is via carrier-free immobilization as cross-linked enzyme aggregates (CLEAs). This methodology proved to be very effective with a broad selection of enzymes, in particular carbohydrate-converting enzymes. Methods for optimizing CLEA preparations by, for example, adding proteic feeders to promote cross-linking, and strategies for making the pores accessible for macromolecular substrates are critically reviewed and compared. Co-immobilization of two or more enzymes in combi-CLEAs enables the cost-effective use of multiple enzymes in biocatalytic cascade processes and the use of “smart” magnetic CLEAs to separate the immobilized enzyme from other solids has raised the CLEA technology to a new level of industrial and environmental relevance. Magnetic-CLEAs of polysaccharide-converting enzymes, for example, are eminently suitable for use in the conversion of first and second generation biomass.

/pdf/cleas-combi-cleas-and-smart-magnetic-cleas-biocatalysis-in-a-4zas31n72p.pdf

Megha Nimbalkar

Papers

Porous cross linked enzyme aggregates (p-CLEAs) of Saccharomyces cerevisiae invertase