Bromelain Immobilized onto Diamine-functionalized Electrospun Polyvinyl Chloride Fibers as a Durable Heterogeneous Catalyst

The best condition to produce smooth polyvinyl chloride (PVC, M.W. ∼6.4×10⁴ g/mol) fibers (572±171 nm) was 10 % w/v PVC in a mixture of tetrahydrofuran and dimethyl sulfoxide (4:1 by volume) with 5 % w/w Tween 20, 15 kV, 10 cm, and 3 ml/h. PVC fibers were subjected to plasma surface treatment to make them more hydrophilic. Diameters of the treated fibers were 549±99 nm. Next, the PVC fibers were treated with ethylene diamine (EDA) and p-phenylenediamine (PDA) to obtain PVC-EDA and PVC-PDA, respectively. Bromelain was immobilized onto PVC-EDA and PVC-PDA by an aid of 1 % w/v glutaraldehyde to receive PVC-EDA-bromelain and PVC-PDA-bromelain with good tensile strengths of ∼19 and ∼14 MPa, respectively. The activities of free and immobilized bromelain were assayed by casein as a substrate and a spectrophotometer at 275 nm. Bromelain loadings on PVC-EDA-bromelain and PVC-PDA-bromelain were 88.10±3.54 and 36.38±18.10 mg/g of fibers, respectively. The kinetic activities of bromelain, PVC-EDA-bromelain, and PVC-PDA-bromelain were 11.31±2.17, 0.31±0.03, and 2.15±1.34 min⁻¹, respectively. PVC-EDA-bromelain and PVC-PDA-bromelain could be reused at least 9 times with > 50 % relative activities and endured heat (50–90 °C) better than free bromelain did. Their relative activities were > 70 % after storage at 90 °C for 20 min.