Xylanase, a glycoside hydrolase, is widely used in the food, papermaking, and textile industries; however, most xylanases are inactive at high temperatures. In this study, a xylanase gene, CFXyl3, was cloned from Cellulomonas flavigena and expressed in Escherichia coli BL21 (DE3). To improve the thermostability of xylanase, four hybrid xylanases with enhanced thermostability (designated EcsXyl1–4) were engineered from CFXyl3, guided by primary and 3D structure analyses. The optimal temperature of CFXyl3 was improved by replacing its N-terminus with the corresponding area of SyXyn11P, a xylanase that belongs to the hyperthermostable GH11 family. The optimal temperatures of the hybrid xylanases EcsXyl1–4 were 60, 60, 65, and 85°C, respectively. The optimal temperature of EcsXyl4 was 30 C higher than that of CFXyl3 (55°C) and its melting temperature was 34.5°C higher than that of CFXyl3. After the hydrolysis of beechwood xylan, the main hydrolysates were xylotetraose, xylotriose, and xylobiose; thus, these hybrid xylanases could be applied to prebiotic xylooligosaccharide manufacturing.
To meet the needs of the underwater vehicle hovering control, the paper developed a digital simulator for water system entities hovering underwater vehicle physics platform. A vector equation of motion underwater vertical transport is created and the deep manipulation of the equations of motion and equilibrium equations is given. Therefore, the underwater vehicle motion parameters is obtained. The injection pressure of the water tank drainage model is established. To further improve the accuracy and make the simulation results close to the actual test, the media flow conduit model, the movement model of the electro-hydraulic ball valve, slothing model of three DOF coupled fluid and multivariate function generator model is established. The motion parameters are also carried into these models to obtain correction coefficient for objective function. The results show that the proposed system has good performance in control precision, synchronization, response time and steady-state error which can meet the engineering requirements of simulating the process of hovering control of actual underwater vehicle.
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