Biocatalysis has become an important part of the synthesis of organic products in the chemical and pharmaceutical industries. Scientists have used nanotechnology in enzyme immobilization strategies, which has significantly increased biocatalysis, improving the production of various vital products.
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What is Biocatalysis?
Biocatalysis is a process that uses natural substances, especially enzymes, to increase the rate of a chemical reaction. Scientists have claimed that enzymes are responsible for catalyzing hundreds of reactions, including the production of cheese, alcohol and biofuel.
Following technological advances, researchers have better understood the structure and functionality of enzymes, helping to design enzymes with improved activity, stability, sustainability, and substrate specificity.
Various biocatalytic processes have been used in the chemical, fragrance, pharmaceutical, food and agricultural industries. Biocatalysis-based research involves discovering new biocatalysts, identifying target reactions, biocatalyst engineering, and modeling processes.
Nanotechnology and Biocatalysts
Enzymes immobilized on support materials offer several advantages, such as high catalytic efficiency, minimal reaction time, increased reuse, simpler downstream processing for continuous scale operation, and a high enzyme-substrate ratio, which reduces operating cost. Enzyme immobilization in various nanomaterials has helped to overcome the shortcoming related to conventional enzyme immobilization processes.
Enzyme immobilization in nanomaterials, also known as nanobiocatalyst, has effectively boosted the reaction process. Various nanostructures, for example nanopores, nanocomposites, nanotubes, nanosheets and nanorods, are used to immobilize biocatalysts. Various enzymes, including beta-glucosidases, lipases, and cellulase, have been reported to be effectively immobilized in various nanoparticles, such as polymeric magnetic nanofibers, manganese dioxide, chitosan magnetic microspheres.
There are different types of nanobiocatalysts, such as transition metal oxide (for example, titanium dioxide nanosulfate), alkaline earth metal oxides (for example, nano calcium oxide), mixed metal oxide (e.g., iron-tin nanomaterials) and supported metal oxide (e.g., nano potassium fluoride / calcium oxide-magnesium oxide). Some of the characteristics of nanobiocatalysis are high activity, stability, selectivity, energy efficiency and ease of separation of the reaction mixture.
In biofuel production, nanobiocatalysts such as graphene, fullerene, titanium dioxide (TiO2) and ferric oxide (Fe3O4) increase the conversion efficiency of biomass. Studies have shown that small nanoparticles with an increased surface area strongly influence their catalytic property by improving the availability of active catalytic sites.
The raw material used to synthesize nanobiocatalysts is sunflower oil, rapeseed oil, soybean oil, jatropha oil and olive oil. Some of the widely used methods for the synthesis of nanobiocatalysts are co-precipitation, sol-gel, sol-gel self-combustion and impregnation.
Depending on the binding capacity of the carrier material to the enzyme, the immobilization process has been classified as covalent bonding, entrapment / encapsulation, crosslinking, and adsorption. In addition, a combinational strategy is also used to better bind nanoparticles with enzymes.
The role of the nanobiocatalyst in the biocatalysis process
There is a high demand for magnetic nanoparticles due to their outstanding immobilizing effect, increased surface-to-volume ratio, and quantum property. These nanoparticles are used to immobilize enzymes, such as cellulase and lipase, for the production of biofuel from a marine microalga (Chlorella salina). Magnetic nanoparticles are popularly used for biocatalysis because they can be easily recovered by a magnetic field.
The scientists said that immobilized enzymes help the large-scale production of biodiesel due to the reuse effect of immobilized enzymes several times. In addition to producing biofuels, immobilized enzymes are also used in the food, pharmaceutical and chemical industries.
Cellulase is an important enzyme used for large-scale production of biofuel. This enzyme is obtained from fungi (e.g., Penicillium, Trichoderma, Aspergillus) and bacteria (e.g., Pseudomonas and Bacillus). In the production of biofuels, scientists have immobilized cellulase enzymes in nanomaterials such as silica, nickel, carbon nanotubes and graphene, which has increased the reuse of the enzyme and decreased the operating cost.
Studies have shown that immobilized cellulase has a higher functional stability than the free enzyme in a wider range of pH and temperatures. These studies have also reported that cellulase immobilized on magnetic nanoparticles produced twenty times higher glucose concentrations compared to free cellulase.
For bioethanol production, cellulosic biomass has been converted to glucose by the process of co-immobilization of cellobiohydrolase D and β-glucosidase A into superparamagnetic nanoparticles. This technique has shown greater enzymatic stability and improved production.
Scientists have also successfully immobilized lipases in magnetic nanocarriers, which not only maintained the specificity, but also improved the stability of the enzyme over a wide range of pH and temperatures.
Studies have shown that lipase from porcine pancreas immobilized on surface-modified magnetic nanoparticles showed improved stability and specificity. In addition, immobilized lipase was easily recovered and reused effectively. Interestingly, for lipase immobilization, metal nanocarriers improved the catalytic efficiency of the enzyme.
Future perspective
Despite the immense potential of biofuels as an alternative source of energy, the commercialization of the biofuel production process has not been up to par. This is mainly due to the lack of efficient biomass conversion techniques in a cost effective manner. The application of nanotechnology in biocatalytic reactions has opened the door to the production of biofuel in a cost-effective way. Currently, scientists have focused on increasing the reuse of nanobiocatalysts, improving their catalytic property, selectivity and stability.
Because nanotechnology-based solutions have been successfully implemented in many industries, scientists are optimistic that in the future, the application of nanobiocatalysts will improve the commercial production of biofuel and other economically important bioproducts.
Continue reading: What is nanochemistry?
References and future readings
Tsriwong, K. and Matsuda, T. (2022) Recent Advances in Enzyme Immobilization Using Nanotechnology for Biocatalysis. Research and development of organic processes.
Sharma, A. et al. (2022) The impact of nanoparticle-based enzyme immobilization on biocatalysis. Nanomaterials for Biocatalysis, pp.149-168. TWO:
Singh, N. et al. (2020) Nanoimmobilized biocatalysts and their potential biotechnological applications in bioenergy production. Materials Science for Energy Technologies, 3, p. 808-824.
Misson, M. et al. (2015) Advances in nanobiocatalysts and bioprocessing applications. Journal of the Royal Society, Interface, 12 (102), 20140891. https://doi.org/10.1098/rsif.2014.0891
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