3.5 Applications of Nanotechnology for the Immobilization of Enzymes and Bioconversion

41

[22]. Bioconjugation of cellulase to graphene oxide hydrogel showed higher stability

and activity. This bioconjugated enzyme was effectively utilized for the hydrolysis

of lignocellulosic biomass, and it increased the hydrolysis of sugar beet pulp [23].

Hydrogel-based ionic liquid-tolerant immobilized cellulase system was built [24].

This system improved the in situ saccharification of biomass [24]. Calcium alginate

immobilized cellulase exhibited high reusability and easy recovery during the

hydrolysis of carboxymethyl cellulose [25]. Hence, immobilized enzymes can be

applied onto the polysaccharide wastes for the easy recovery of antioxidants, sugars,

and other metabolites.

3.4.4

Lipids as Substrates

The valorization of lipid waste is highly significant with respect to environmental

impact and economy. High value-added products like lubricants, biodiesel, surfac-

tants, and so on can be obtained from waste oils by enzymatic treatment. Polymeric

resins have also been practiced to obtain biodiesel, surfactants, fatty acids, etc., from

waste oils by immobilizing lipases on them [3]. The higher levels of biodiesel were

obtained from the waste cooking oil using multi-enzyme system based on covalently

immobilized lipases from Rhizomucor miehei and lipase B from Candida antarctica.

These enzymes were immobilized onto epoxy-functionalized silica. Very high pro-

duction (91.5%) of fatty acid methyl esters (FAME) has been recorded after 10 hours

of reaction time [26].

Near carbon dioxide neutrality makes biodiesel as environmental-friendly fuel.

Immobilized lipases will become the sustainable catalysts for the production of

biodiesel due to their reusability, efficiency, and easy separation. Lipid wastes

from different sectors will drive the need for immobilized lipases. Lipase

from C. rugosa was immobilized onto composite of Fe3O4 and poly(glycidyl-

methacrylate-co-methacrylic acid). This immobilized enzyme gave the 92% yield

of biodiesel from the transesterification reaction of soybean oil, and this lipase was

easily recovered by applying external magnetic field [27]. Immobilized lipase EQ3

was used along with commercial lipozyme RMIM for the conversion of coconut oil

into liquid wax esters which can be used in the manufacture of cosmetics and skin

care products [28]. Lipase immobilized on the activated carbon was used for the

synthesis of aromatic esters [29].

3.5

Applications of Nanotechnology for the

Immobilization of Enzymes and Bioconversion

Nanoparticles generally have two drawbacks while they have been used as carriers

for the enzymes: first one is clump formation due to temporary dispersion with

sonication process and second one is difficulty during separation due to their small

size. Superparamagnetism is one solution for these problems, where a material

becomes magnetic only in the existence of a magnetic field. Particles of such

materials can be easily dispersed in the solution and recovered by the usage of a