Immobilization of Cellulase on a Functional Inorganic–Organic Hybrid Support: Stability and Kinetic Study

Abstract

Abstract:Cellulase from Aspergillus niger was immobilized on a synthesized TiO 2 -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.

Synergistic Degradation of Dye Wastewaters Using Binary or Ternary Oxide Systems with Immobilized Laccase

“…Regarding the degradation of dyes at 5 • C, a significant reduction in process efficiency can be noticed. This fact is caused by conformational changes in the laccase structure [43] and a reduction of enzymatic activity at low temperatures, as was previously reported [44]. Nevertheless, it is worth mentioning that even at high temperature, degradation of the selected dyes occurs more efficiently than simple sorption, which means that the enzyme works and its activity is visible even at 5 and 50 • C. Reda et al also investigated the effect of temperature on the degradation efficiency of synthetic dyes (including Methyl Red, Congo Red, Trypan Blue, RBBR and Aniline Blue) using laccase immobilized on various supports, such as Ca-alginate, agarose-agar, alginate-gelatin mixed gel, and polyacrylamide gel [45].…”

Adsorption Kinetics of Cellulase and Xylanase Immobilized on Magnetic Mesoporous Silica

“…The charged surface of the support and its ionic interaction with the enzyme were the cause of the shifts in pH optimum after immobilization [49]. This might be explained by the fact that, in a basic environment, ionic groups present in the xylanase molecules result in an electrostatic repulsion that influences the three-dimensional structure of the enzyme, leading to disruption and destruction of the active sites of the xylanase, and thus impairing its catalytic properties [52]. An increase in alkalinity in the reaction system up to pH 8 resulted in a decrease in activity by 67.31 % and 39.63 % of the immobilized cellulase and xylanase as obtained in the systems with a pH of 5 and 3.…”

“…Moreover, the catalytic properties are significantly better in acidic than in alkaline conditions. This might be explained by the fact that, in a basic environment, ionic groups present in the xylanase molecules result in an electrostatic repulsion that influences the three-dimensional structure of the enzyme, leading to disruption and destruction of the active sites of the xylanase, and thus impairing its catalytic properties [52]. As shown in Fig.…”

Immobilized Biocatalysts

“…The immobilized cells retained 100% metabolic activity for at least 10 working cycles. An inorganic/organic hybrid support TiO 2 -lignin was employed by Zdarta et al [44] for the immobilization of a cellulase from Aspergillus niger. As is to be seen from the fact that the half-life of the immobilized cellulase was five times that of the free enzyme and over 90% of its initial catalytic was retained after ten repeated cycles, the hybrid support contributed to a significant improvement of the enzyme's thermal and chemical stability.…”