Abstract
Cellulase from Aspergillus niger was immobilized on a synthesized TiO2–lignin hybrid support. The enzyme was effectively deposited on the inorganic–organic hybrid matrix, mainly via physical interactions. The optimal initial immobilization parameters, selected for the highest relative activity, were pH 5.0, 6 h process duration, and an enzyme solution concentration of 5 mg/mL. Moreover, the effects of pH, temperature, and number of consecutive catalytic cycles and the storage stability of free and immobilized cellulase were evaluated and compared. Thermal and chemical stability were significantly improved, while after 3 h at a temperature of 50 °C and pH 6.0, the immobilized cellulase retained over 80% of its initial activity. In addition, the half-life of the immobilized cellulase (307 min) was five times that of the free enzyme (63 min). After ten repeated catalytic cycles, the immobilized biocatalyst retained over 90% of its initial catalytic properties. This study presents a protocol for the production of highly stable and reusable biocatalytic systems for practical application in the hydrolysis of cellulose.
Highlights
Cellulases are classified as hydrolytic enzymes [1] and include at least three types of biocatalysts: endo-(1,4)-β-D-glucanase (EC 3.2.1.4), exo-(1,4)-β-D-glucanase (EC 3.2.1.91), and β-glucosidases (EC 3.2.1.21) [2,3,4]
Cellulases are responsible for the process of depolymerization of cellulose by delamination of the cell walls, which is a consequence of cellulose hydrolysis [1,6]
Commercial cellulases have been available for several decades, and have found applications in several important branches of industry, in the wood and cellulose-paper industries, as well as in other branches including the conservation of thermoplastic polymers and plastics, bioconversion of cellulosic materials to organic solvents, fermentation processes, detergents, textiles, laundry, and the food and feed industries [9]
Summary
Cellulases are classified as hydrolytic enzymes [1] and include at least three types of biocatalysts: endo-(1,4)-β-D-glucanase (EC 3.2.1.4), exo-(1,4)-β-D-glucanase (EC 3.2.1.91), and β-glucosidases (EC 3.2.1.21) [2,3,4] They are produced by bacteria and microbes; the main enzyme acquisition process is based on fungi, which provide the highest production index [1,5,6]. Cellulases are responsible for the process of depolymerization of cellulose by delamination of the cell walls, which is a consequence of cellulose hydrolysis [1,6] These biocatalysts have numerous practical applications in many fields of industry and agriculture. In view of the broad application of these enzymes, it is necessary to develop novel and more stable materials to enable the aforementioned processes to be carried out more efficiently
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