Probing the limitations for recycling cellulase enzymes immobilized on iron oxide (Fe3O4) nanoparticles
Document Type
Article
Publication Date
3-1-2014
Abstract
A major determining factor for a viable cellulosic ethanol industry is the utilization of cellulase enzymes in a more cost-efficient manner during the hydrolytic process. The hydrophobic nature of the enzyme and inhibition by reaction intermediates and end products greatly decreases its efficacy following the initial reaction. To improve efficiency and lower enzyme costs, a method for recycling cellulase enzymes by immobilization on Fe3O4 nanoparticles was evaluated. The Fe3O4 particles used had a mean diameter of 13 nm and carbodiimide activation was employed for enzyme immobilization. The immobilized enzyme complex retained 30.2 % of the free enzyme activity and was successfully recycled six times with a reduction in activity following each recycle. An activity loss of 47.5 % resulted following the initial hydrolysis reaction, after which a more gradual loss ensued. A protein assay performed on the reaction supernatant confirmed varying degrees of enzyme detachment following each recycle. However, immobilized enzymes were determined to have higher stability as compared to free enzyme when assessing their activities over time. Following 72 h of hydrolysis, immobilized enzymes retained 57.9 % of their activity, which was slightly better than the 51.2 % retained by free enzyme. From a practicality point of view, a performance comparison of enzyme-bound nanoparticles over all recycles determined that total reducing sugars produced after 96 h of hydrolysis was 76.8 % of that produced by a single reaction with free enzyme, therefore indicating a need for deeper understanding and improvements in the enzyme recycling process. Further probing indicated that the contribution from enzyme activity loss far exceeds any possible losses from enzyme detachment. © 2013 Springer-Verlag Berlin Heidelberg.
Publication Source (Journal or Book title)
Biomass Conversion and Biorefinery
First Page
25
Last Page
33
Recommended Citation
Jordan, J., & Theegala, C. (2014). Probing the limitations for recycling cellulase enzymes immobilized on iron oxide (Fe3O4) nanoparticles. Biomass Conversion and Biorefinery, 4 (1), 25-33. https://doi.org/10.1007/s13399-013-0089-z