Immobilized enzyme

About: Immobilized enzyme is a research topic. Over the lifetime, 15282 publications have been published within this topic receiving 401860 citations.

Kinetic studies of lipase from Candida rugosa: a comparative study between free and immobilized enzyme onto porous chitosan beads.

Abstract: The search for an inexpensive support has motivated our group to undertake this work dealing with the use of chitosan as matrix for immobilizing lipase. In addition to its low cost, chitosan has several advantages for use as a support, including its lack of toxicity and chemical reactivity, allowing easy fixation of enzymes. In this article, we describe the immobilization of Candida rugosa lipase onto porous chitosan beads for the enzymatic hydrolysis of olive oil. The binding of the lipase onto the support was performed by physical adsorption using hexane as the dispersion medium. A comparative study between free and immobilized lipase was conducted in terms of pH, temperature, and thermal stability. A slightly lower value for optimum pH (6.0) was found for the immobilized form in comparison with that attained for the soluble lipase (7.0). The optimum reaction temperature shifted from 37 degrees C for the free lipase to 50 degrees C for the chitosan lipase. The patterns of heat stability indicated that the immobilization process tends to stabilize the enzyme. The half-life of the soluble free lipase at 55 degrees C was equal to 0.71 h (Kd = 0.98 h(-1)), whereas for the immobilized lipase it was 1.10 h (Kd = 0.63 h(-1)). Kinetics was tested at 37 degrees C following the hydrolysis of olive oil and obeys the Michaelis-Menten type of rate equation. The Km was 0.15 mM and the Vmax was 51 micromol/(min x mg), which were lower than for free lipase, suggesting that the apparent affinity toward the substrate changes and that the activity of the immobilized lipase decreases during the course of immobilization.

Tuning Pore Heterogeneity in Covalent Organic Frameworks for Enhanced Enzyme Accessibility and Resistance against Denaturants

Abstract: Achieving high-performance biocomposites requires knowledge of the compatability between the immobilized enzyme and its host material. The modular nature of covalent organic frameworks (COFs), as a host, allows their pore geometries and chemical functionalities to be fine-tuned independently, permitting comparative studies between the individual parameters and the performances of the resultant biocomposites. This research demonstrates that dual pores in COFs have profound consequences on the catalytic activity and denaturation of infiltrated enzymes. This approach enforces a constant pore environment by rational building-block design, which enables it to be unequivocally determined that pore heterogeneity is responsible for rate enhancements of up to threefold per enzyme molecule. More so, the enzyme is more tolerant to detrimental by-products when occupying the larger pore in a dual-pore COF compared to a corresponding uniform porous COF. Kinetic studies highlight that pore heterogeneity facilitates mass transfer of both reagents and products. This unparalleled versatility of these materials allows many different aspects to be designed on demand, lending credence to their prospect as next-generation host materials for various enzyme biocomposites catalysts.

Screen-printed biosensors using different alcohol oxidases

Abstract: Low-cost screen-printed sensors consisting of a platinum working electrode, a carbon counter electrode, and an Ag/AgCl pseudo-reference electrode were fabricated for the development of alcohol oxidase biosensors. The sensors were fabricated as amperometric transducers for the detection of alcohols in batch systems. A mixture of alcohol oxidase (AOD) with poly(carbamoyl)sulfonate (PCS) hydrogel was used for enzyme immobilization onto the platinum electrodes. Alcohol oxidases from different sources such as from Hansenula sp., from Candida boidinii and from Pichia pastoris were used for immobilization. The performances of the resulting different sensors has been compared and characterized with respect to enzyme load, pH and temperature dependence, response time, recovery time, linear range and sensitivity. The relative response of sensors for different alcohols was measured to evaluate the selectivity of the sensors. The effect of ascorbic acid and sodium sulfite as electrochemical interferents on the sensor’s performance was investigated. The continuous operation and storage stability of the sensors were also evaluated. Most of the characterization parameters were found to be superior for sensors with immobilized AOD from Hansenula sp. The sensors were also tested with wine samples. The results obtained by the newly developed biosensors were compared to results obtained by pycnometry, the well-established reference method as well as gas chromatograph method.