Preparation Of Magnetic Biochar Immobilized Cellulase And Its Application In Hydrolysis Of 1,4-Glycosidic Bonds

As the global economy advances,the depletion of fossil fuel and the resultant serious environmental pollution become obvious.The development of renewable resources such as biomass proves to be become an urgent priority.the immobilization of cellulase on various support is considered as a green approach for the production of glucose from hydrolysis of cellulose,in which efficient catalytic activity and good reusability are simultaneously satisfied and it is even applicable in harsh conditions.as a new type of support with high specific surface area and porous structure,biochar is easy to prepare and magnetizable,which endow it with unique advantages in the field of immobilized enzymes.Therefore,in this thesis,magnetically separable biochar as a support was designed and prepared from different biomasses and was subsequently used to immobilize cellulase.The optimal preparation conditions forthe magnetic biochar were studied;the optimal immobilization conditions for immobilizing cellulase and the relative enzyme activities at different p H and temperature conditions were investigated,and the adsorption mechanism of cellulase adsorption by the magnetic biochar was explored.Finally,the effect of different biochar with immobilized enzyme on the hydrolysis of 1,4-glycosidic bonds using different model reactant was demonstrated.The main contents and related results are as follows:(1)The formation of Fe3O4 in the magnetic biochar support was significantly influenced by the calcination temperature and calcination time.The structure of Fe3O4 was destroyed under over 600?;60min.The optimum calcination conditions for the preparation of magnetic biochar from the three raw materials were: Metasequoia at 500?;60min;Bamboo powder at 600?;60min;Miscanthus at 600?;60min.(2)The optimal immobilization conditions for the immobilization of cellulase on magnetic biochar are as follows: the immobilization temperature is 50?,and the input amount of the support is 50 mg;the maximum cellulase immobilization capacity of the magnetic biochar carrier reaches 484.36 mg/g;The optimal enzyme activity conditions of immobilized cellulase were p H=5,60?,the optimal enzyme activity conditions of free cellulase were p H=5,50?,and the temperature tolerance of immobilized enzyme was improved compared with free enzyme;The results were found to be close to the Freundlich model(R2=0.832)by fitting model equations to the adsorption process of cellulase on magnetic biochar;the results were close to the pseudo-second-order model(R2=0.982)by fitting model equations to the adsorption mechanism,indicating that the adsorption process included physical adsorption and chemical adsorption,and the adsorption rate was determined by both physical adsorption and chemical adsorption.(3)The optimal yields of cellulase immobilized on magnetic biochar in the hydrolysis of cellobiose,dextran and microcrystalline cellulose were 932.5 mg/g,218.5 mg/g,and 643mg/g,respectively;When cellobiose was used as the reaction substrate and the feeding ratio was 7:1,the glucose yield was 977.13 mg/g,and the conversion rate was 97.71%;the glucose yield reached 705.8 mg/g at 5h,977.13mg/g at 24 h,The yield of 5h of hydrolysis reached 72.23% of 24h;the immobilized enzyme still maintained 51.76% of the initial activity after 10-time reusability.