Mass Transfer and Reaction in Hydrolysis of Coconut Husk Using Immobilized Enzyme on Chitosan Magnetic Nanoparticle

Abstract

A more sustainable energy source is needed to fulfill the increasing demand for energy. In Indonesia, biomass waste utilization as biofuel source shows high potential. Coconut husk is a biomass comprised of cellulose and hemicellulose that can converted to reducing sugar through enzymatic hydrolysis and can be further converted into biofuel. However, enzymatic hydrolysis is expensive, as enzyme is soluble and cannot be separated after use. Immobilization is a technique where an enzyme is trapped onto an insoluble inert support material so that the enzyme can be recovered and reused. Chitosan magnetic nanoparticles (CMNP) are used in this experiment as the support as it is cheap and readily available. Since coconut husk is insoluble, mass transfer phenomena remains a major bottleneck in hydrolysis due to limitations in the substrate to enzyme accessibility, especially when the enzyme is immobilized on an insoluble material like CMNP. If only mass transfer resistance is accounted, hydrolysis only occurs on the enzyme particles’ surface. The mass transfer coefficients obtained are 0.0000723, 0.0368, 0.0295 in respect of A. niger cellulase, T. reesei cellulase, and T. longibrachiatum xilanase. Higher coefficients values contribute proportionally to higher yield. If the reaction is assumed to occur uniformly within the spherical immobilized enzyme, then the substrate will diffuse molecularly through the enzyme, where internal mass transfer is no longer negligible. Thiele’s Modulus obtained are 2.197, 0.0368, 0.0795 in respect of A. niger cellulase, T. reseei cellulase, and T. longibrachiatum xilanase. A smaller value in Thiele’s Modulus (ϕ ≤ 1) shows that diffusion occurs at a faster rate than the enzymatic reaction.