PROCESS BIOCHEMISTRY, vol.113, pp.270-280, 2022 (SCI-Expanded)
The immobilization of xylanase from Trichoderma longibrachiatum via ion exchange on 3-propylsulfonic acid (Xyl/Si-SO3) and 3-aminopropyl (Xyl/Si-NH3) functionalized silica gel and covalently on 3-carboxypropyl (Xyl/ Si-COOH) and silica gel functionalized with 3-aminopropyl and modified with glutaraldehyde (Xyl/Si-Glu) were performed and the prepared biocatalysts were used for clarification of orange juice. The supports and immobilized biocatalysts were characterized by scanning electron microscopy, and thermal gravimetric analysis. Free and all immobilized xylanase samples showed maximal catalytic activity at pH 6.0. The free xylanase and Xyl/SiNH3 had a maximal catalytic activity at 50 degrees C, while Xyl/Si-Glu, Xyl/Si-COOH and Xyl/Si-SO3 exhibited their maximal catalytic activities at 60 C. The Xyl/Si-Glu showed 4.2-fold higher thermal stability than the free xylanase at 50 degrees C and pH 6.0. The clarity of orange juice was increased by 74.7, 73.6, 59.3, 60.3, and 78.8 % respectively by using free xylanase, Xyl/Si-Glu, Xyl/Si-COOH, Xyl/Si-SO3 and Xyl/Si-NH3 at 50 degrees C after 180 min treatment time. The reusability studies showed that Xyl/Si-Glu, Xyl/Si-COOH, Xyl/Si-SO3 and Xyl/Si-NH3 retained 77, 71, 11 and 16 %, respectively, of their initial activities after 10 reuses. These results show that Xyl/ Si-Glu and Xyl/Si-COOH are better potential candidates than Xyl/Si-SO3 and Xyl/Si-NH3 in fruit juice clarifying processes.