Pectin hydrolysis in a free enzyme membrane reactor: An approach to the wine and juice clarification

In this paper, a long-term investigation of the enzyme hydrolysis of pectin, using a free enzyme membrane reactor (FEMR), is presented. Production of crude enzymes (polygalacturonase and pectin lyase), in Aspergillus niger CECT 2088 cultures grown on an agricultural subproduct (apple pomace) as a low cost inducer, was also studied. Observing the retention of induced pectinases by the ultrafiltration membranes, the best FEMR configuration was achieved with the membrane of 10,000 nominal molecular weight limit (NMWL), since the biocatalyst was retained with no loss of enzyme activity. The monitoring of pectin hydrolysis in the FEMR was carried out by determining the viscosity and amount of reducing groups in both reaction mixture and permeate. A viscosity reduction of 88%, below the initial value, was reached in the reaction mixture only after 0.25 h of operation, while a gradual release of reduced sugars, in both reaction mixture and permeate, was detected. The FEMR was maintained in operation for 15 days, achieving an excellent catalytic efficiency.