Effect of cellulose physical characteristics, especially the water sorption value, on the efficiency of its hydrolysis catalyzed by free or immobilized cellulase

• Published in: Journal of biotechnology 2012-01, Vol.157 (1), p.246-252
• Main Authors: Ogeda, Thais L., Silva, Igor B., Fidale, Ludmila C., El Seoud, Omar A., Petri, Denise F.S.
• Format: Article
• Language: English
• Subjects: active sites; Adsorbed cellulase; Adsorption; Biological and medical sciences; biopolymers; Biotechnology; catalysts; catalytic activity; cellobiose; Cellulase - chemistry; Cellulase - metabolism; Cellulose; Cellulose - chemistry; Cellulose - metabolism; Cellulose - ultrastructure; cotton; crystal structure; endo-1,4-beta-glucanase; Enzymes, Immobilized - chemistry; Enzymes, Immobilized - metabolism; Equipment Reuse; Eucalyptus; Free cellulase; Fundamental and applied biological sciences. Psychology; Fungal Proteins - chemistry; Fungal Proteins - metabolism; glucose; Hydrolysis; immobilized enzymes; phosphoric acid; polymerization; Porosity; recycling; sorption; Trichoderma - enzymology; Water - chemistry; Water - metabolism; Water sorption
• ISSN: 0168-1656; 1873-4863
• DOI: 10.1016/j.jbiotec.2011.11.018

► Strong cellulose water sorption ability favors cellulose enzymatic hydrolysis. ► Cellulose physical characteristics had no effect on the efficiency of immobilized cellulase. ► Immobilized cellulase could be reused six times without appreciable loss of catalytic activity. Cellulase, an enzymatic complex that synergically promotes the degradation of cellulose to glucose and cellobiose, free or adsorbed onto Si/SiO2 wafers at 60°C has been employed as catalyst in the hydrolysis of microcrystalline cellulose (Avicel), microcrystalline cellulose pre-treated with hot phosphoric acid (CP), cotton cellulose (CC) and eucalyptus cellulose (EC). The physical characteristics such as index of crystallinity (IC), degree of polymerization (DP) and water sorption values were determined for all samples. The largest conversion rates of cellulose into the above-mentioned products using free cellulase were observed for samples with the largest water sorption values; conversion rates showed no correlation with either IC or DP of the biopolymer. Cellulose with large water sorption value possesses large pore volumes, hence higher accessibility. The catalytic efficiency of immobilized cellulase could not be correlated with the physical characteristics of cellulose samples. The hydrolysis rates of the same cellulose samples with immobilized cellulase were lower than those by the free enzyme, due to the diffusion barrier (biopolymer chains approaching to the immobilized enzyme) and less effective contact between the enzyme active site and its substrate. Immobilized cellulase, unlike its free counterpart, can be recycled at least six times without loss of catalytic activity, leading to higher overall cellulose conversion.