Immobilization of Phospholipase A1 and its Application in Soybean Oil Degumming

Phospholipase A(1) (PLA(1)), or Lecitase (R) Ultra, was immobilized on three different supports, calcium alginate (CA), calcium alginate-chitosan (CAC), and calcium alginate-gelatin (CAG), and crosslinked with glutaraldehyde. The results indicated that PLA(1)-CA retained 56.2% of the enzyme's initial activity, whereas PLA(1)-CAC and PLA(1)-CAG retained 65.5 and 60.2%, respectively. Compared with free PLA(1), the optimal pH of immobilized PLA(1) shifted to the basic side by 0.5-1.0 pH units and the pH/activity profile range was considerably broadened. Similarly, the temperature-optima of PLA(1)-CAC and PLA(1)-CAG increased from 50 to 60 degrees C, and their thermal stability increased with relative activities of more than 90% that covered a wider temperature range spanning 50-65 degrees C. In a batch oil degumming process, the final residual phosphorus content was reduced to less than 10 mg/kg with free PLA(1), PLA(1)-CAC and PLA(1)-CA in less than 5, 6 and 8 h respectively while PLA(1)-CAG was only able to reduce it to 15 mg/kg in 10 h. When the PLA(1)-CAC was applied in a plant degumming trial, the final residual phosphorus content was reduced to 9.7 mg/kg with 99.1% recovery of soybean oil. The recoveries of immobilized PLA(1)-CAC and activity of PLA(1) were 80.2 and 78.2% respectively. Therefore, it was concluded that PLA(1)-CAC was the best immobilized enzyme complex for the continuous hydrolysis of phospholipids in crude vegetable oils.