Cross-linked enzyme aggregates of arylamidase from Cupriavidus oxalaticus ICTDB921: process optimization, characterization, and application for mitigation of acrylamide in industrial wastewater

Acrylamidase produced by Cupriavidus oxalaticus ICTDB921 was recovered directly from the fermentation broth by ammonium sulfate (40-50%) precipitation and then stabilized by cross-linking with glutaraldehyde. The optimum conditions for the preparation of cross-linked enzyme aggregates of acrylamidase (acrylamidase-CLEAs) were using 60 mM glutaraldehyde for 10 min at 35 degrees C and initial broth pH of 7.0. Acrylamidase-CLEAs were characterized by SDS-PAGE, FTIR, particle size analyzer and SEM. Cross-linking shifted the optimal temperature and pH from 70 to 50 degrees C and 5-7 to 6-8, respectively. It also altered the secondary structure fractions, pH and thermal stability along with the kinetic constants, K-m and V-max, respectively. A complete degradation of acrylamide similar to 1.75 g/L in industrial wastewater was achieved after 60 min in a batch process under optimum operating conditions, and the kinetics was best represented by Edward model (R-2 = 0.70). Acrylamidase-CLEAs retained similar to 40% of its initial activity after three cycles for both pure acrylamide and industrial wastewater, and were stable for 15 days at 4 degrees C, retaining similar to 25% of its original activity.