Cellulose Enzyme Degradation Of Cellulose Role In Ionic Liquids

In this paper, three acetate-based ionic liquid was synthesized to study the initial enzymeactivity, the residual enzyme activity and thermal stability of cellulose enzyme were in them.We found that the optimum pH for the cellulase enzyme to survive4.7in our work, andmeanwhile, the existence of ionic liquids can inhibit the activity of cellulase enzyme. Theinhibition effect would be greater along with the concentration of ionic liquids The inhibitioneffect of ionic liquids on cellulose enzyme activity is decreased in the order [Emim] OAc>[Bmim] OAc>[C6mim] OAc. The optimum temperature of cellulose enzyme in buffersolution is45℃, when those in the ionic liquids with low concentration and highconcentration is50℃and70℃, respectively, which means that ionic liquids with highconcentration is bennifit for the maintain of cellulose enzyme activity in higher tempurature.Taking the conclusions above into consideration, the use of10%[Emim] OAc ionic liquidswould give a very good degradation effect on cellulose enzyme, which is helpful to run the"one-step" degradation reaction.Under general situations, the optimum degradation conditions for cellulose enzyme is asfollows:0.1g cellulose,45℃, pH value of4.7, dosage of enzyme is0.15g under24h, andthe best degradation rate was28.3%.In the system of10%[Emim] OAc,"one-step" route was used on the cellulose enzymedegradation reaction with orthogonal experiments. The results showed that, the influencingfactors of the degradation rate is in the order temperature> pH> enzyme dosage> reactiontime, and the best conditions is50℃, pH=4.7,0.18g,24h, under which the hydrolysis rateof cellulose to sugar was46.9%, when it by the "two-step" process can reach61.4%.Comparing these three methods, we can see that enzyme degradation rate by the one-stepprocess was1.7times of that under conventional conditions, at the same time, which by atwo-step process was2.2times of the degree under conventional conditions. These resultsshown that ionic liquid is conducive to the dissolution of cellulose, and in favor of thedegradation of cellulose by cellulose enzyme. The use of one-step process could avoid the tedious processes of dissolution and regeneration, with enzymatic hydrolysis sugar rateimproved. So we could make a conclusion that one-step method is superior to other two ways.Through the characterization of cellulose and regenerated cellulose, it can be seen thatcellulose treated by ionic liquid would not take derivatization reaction, but with a transferfrom cellulose Ⅰinto cellulose Ⅱ. The crystal transfer destroyed the original crystalline ofcellulose, and the degree of crystallinity is reduced greatly; the refractory macromolecularstructure of cellulose was translate to the easily dissolving small molecules, thus increase theaction point of cellulase, with strengthened the ability of cellulose enzyme on the degradationof cellulose.