The role of water on the equilibrium of esterification by immobilized lipase packed-bed column reactor
SummaryThe role of water on the continous synthesis of geranyl esters by immobilized lipase fromHumicola lanuginosa No. 3 was studied in a packed-bed column reactor (PBR) installed with a molecular sieve column for water extraction. The conversion degress by PBR were highly influenced by the water concentration throughout the reaction which acted as a determinant on the reaction equilibrium. Almost 100% conversion of geranyl laurate could be achieved under the optimum water-controlled conditions. The stability of the PBR system was for 35 days with the half-life of 38 days.
Characteristics of poly(AAc5‐co‐HPMA3‐cl‐EGDMA15) hydrogel‐immobilized lipase of Pseudomonas aeruginosa MTCC‐4713
Four series of noble networks were synthesized with acrylic acid (AAc) copolymerized with varying amount of 2-hydroxy propyl methacrylate or dodecyl methacrylate (AAc/HPMA or AAc/DMA; 5:1 to 5:5, w/w) in the presence of ethylene glycol dimethacrylate (EGDMA; 1, 5, 10, 15, and 20%, w/w) as a crosslinker and ammonium per sulfate (APS) as an initiator. Each of the networks was used to immobilize a purified lipase from Pseudomonasaeruginosa MTCC-4713. The lipase was purified by successive salting out with (NH4)2SO4, dialysis, and DEAE anion exchange chromatography. Two of the matrices, E15a, i.e. [poly (AAc5-co-DMA1-cl-EGDMA15)] and I15c, i.e. [poly (AAc5-co-HPMA3-cl-EGDMA15)], that showed relatively higher binding efficiency for lipase were selected for further studies. I15c-hydrogel retained 58.3% of its initial activity after 10th cycle of repetitive hydrolysis of p-NPP, and I15c was thus catalytically more stable and efficient than the other matrix. The I15c-hydrogel-immobilized enzyme showed maximum activity at 65°C and pH 9.5. The hydrolytic activity of free and I15c-hydrogel-immobilized enzyme increased profoundly in the presence of 5 mM chloride salts of Hg2+, NH4+, Al3+, K+, and Fe3+. The immobilized lipase was preferentially active on medium chain length p-nitrophenyl acyl ester (C:8, p-nitrophenyl caprylate). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4636–4644, 2006
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.