Diisooctyl 2,5-furandicarboxylate (DEF), an ester derivative of 2,5-furandicarboxylic acid (FDCA, a bio-based platform chemical), resembles the physical and chemical properties of phthalates. Due to its excellent biodegradability, DEF is considered a safer alternative to the hazardous phthalate plasticizers. Although FDCA esters are currently mainly produced by chemical synthesis, the enzymatic synthesis of DEF is a green, promising alternative. The current study investigated the biosynthesis of DEF by Candida antarctica lipase B (CALB) immobilized on macroporous resins. Out of five macroporous resins (NKA-9, LX-1000EP, LX-1000HA, XAD-7HP, and XAD-8) evaluated, the LX-1000EP epoxy resin was identified as the best carrier for CALB, and the XAD-7HP weakly polar resin was identified as the second best. The optimal immobilization conditions were as follows: CALB (500 μL) and LX-1000EP (0.1 g) were incubated in phosphate butter (20 mM, pH 6.0) for 10 h at 35°C. The resulting immobilized CALB (EP-CALB) showed an activity of 639 U/g in the hydrolysis of p-nitrophenyl acetate, with an immobilization efficiency of 87.8% and an activity recovery rate of 56.4%. Using 0.02 g EP-CALB as the catalyst in 10 mL toluene, and the molar ratio of 2,5-dimethyl furanediformate (1 mmol/mL) and isooctyl alcohol (4 mmol/mL) that was 1:4, a DEF conversion rate of 91.3% was achieved after a 24-h incubation at 50°C. EP-CALB had similar thermal stability and organic solvent tolerance compared to Novozym 435, and both were superior to CALB immobilized on the XAD-7HP resin. EP-CALB also exhibited excellent operational stability, with a conversion rate of 52.6% after 10 repeated uses. EP-CALB could be a promising alternative to Novozym 435 in the biomanufacturing of green and safe plasticizers such as DEF.
Keywords: diisooctyl 2,5-furandicarboxylate; enzyme catalysis; macroporous epoxy resin.
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