Xylanase enzyme from novel strain and its immobilization onto metal organic framework MOF for fruit juice clarification

Bacillus pumilus, a bacterial strain was isolated from agricultural soil and used for xylanase enzyme (Xy) production under the submerged fermentation technique. The (Xy) enzyme had an optimum temperature at 50℃ (maximum activity from 45–60 °C) and was active at broad pH range (5.0–8.0) with an optimum pH at around 6.3 as evaluated from response surface methodology studies. This enzyme after purification (purification; 2.87 folds, specific activity; 64.3 U/mg) was immobilized onto MOF_Cu-BTC (a copper ion-based metal organic framework) and was used for clarification of freshly squeezed fruit juice (pineapple and pomegranate). The study revealed an improved catalytic efficiency (V_max from 1.252.5 to 1.361 U/mL/mg of support) and greater half-life of the immobilized system (77–99 min). The activation energy decreased from that required for the free system (37.59–25.63 kJ/mol). The reusability of the enzyme improved after immobilization where 61% of the enzyme’s activity was retained after 21 cycles of usage. The MOF_Xy-Cu-BTC system showed improved clarification (47.58–57.97% for pineapple, and 15.34–18.3 for pomegranate) thereby showing its effectiveness in commercial juice clarification process.