Title

Enzymatic Hydrolysis of Paulownia Pulp

Date of Award

4-3-2018

Semester of Degree

May

Document Type

Open Access Thesis

Major Professor

Shijie Liu

Steering Committee Member

Bandaru V. Ramarao

Steering Committee Member

Gary M. Scott

Steering Committee Member

Thomas E. Amidon

Abstract

As one of the most abundant polymers on earth, cellulose is an important industrial raw material and source of renewable energy. The enzymatic hydrolysis of cellulose to glucose by cellulase is one of the major methods to convert lignocellulosic biomass to biofuel and biomaterials. Enzymatic hydrolysis, catalyzed by cellulase, is a heterogeneous reaction, which is influenced by characteristics of cellulose (e.g. crystallinity, the degree of polymerization and accessible surface area) and other biomass components (lignin and hemicellulose). In this study paulownia pulp, after hot-water pretreatment and delignification was utilized as the substrate while a preparatory commercial cellulase composed of endoglucanase, exo-glucanase, and β-glucosidase was employed as the catalyst. The effect of temperature and pH were investigated. In the temperature experiment, the highest yield of sugar was reached at 55°C in 72 hours. For the pH, the highest conversion was achieved at 4.8 in 96 hours. Kinetic studies were performed with different enzyme loadings. Proton NMR was used for the quantification of glucose and cellobiose. The highest glucose yield in 166 hours was found to be 62.5% at 18.5FPU/g while cellobiose remained at a low and constant concentration during the process. A kinetic model was developed based on a proposed mechanism to explain the production of glucose. The hydrolysis rate was found to increase with increasing temperature at short reaction times, while decrease with increasing temperature at long reaction times. The kinetic model optimized with one set of data was further tested with a different set of enzymatic hydrolysis data.

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