Synthesis and characterization of cellulase dextran conjugates

Cellulases are most commonly used in textile, paper, detergent and food industries. The conditions used in biotechnical processes (temperature, pH) may be different from the physiological conditions in which enzymes operate optimally. Hence, the studies which aim to increase the stability of enzymes by gene technology and/or chemical modification are becaming important. The traditional division of cellulase is based on its mode of action. Exo- enzymes cleave sugar units from the ends of polysaccharide chain, whereas endo-enzymes make more random cuts along the chain. Exo and endo enzymes act cooperatively, or synergistically on cristalline substrates. The current hypothesis to explain endo-exo synergism of cellulase is that endo-acting enzymes provide new chain ends for the exo-acting enzymes. In this study, cellulase from Aspergillus niger was examined. The purchased cellulase was purified by using size exclution column chromatography with Sephadex G- 50, and PBS buffer, pH 7,2 Dekstran (Mw 75 000) was covalently bound to enzyme after oxidation to its aldehyde derivative by using NaIO4. Dekstran-cellulase covalent conjugates were synthesized in different ratio. Conjugates was analysed with HPLC and GPC (4 detectors UV, light scattering, refractive index, viscocity) systems. The activities of the pure enzymes and conjugates has been measured after 0, 30, 60 minutes waiting at 40oC, 50o C, 60oC, 70o C, 80o C for pH 5. The optained results showed that the activities of two conjugates ( Molar ratio 1/5, 1/1 ) were higher than pure enzyme, whreas the other two conjugates has similar activities with enzyme. Key words: Aspergillus niger cellulase, Cellulase-Dextran conjugates, activity, GPC, HPLC, Zeta-sizer