Influence of immobilization parameters on endopolygalacturonase productivity by hybrid Aspergillus sp. HL entrapped in calcium alginate

Culture cells of the hybrid Aspergillus HL were immobilized in calcium alginate beads. Different spore concentrations and bead sizes produced surfaces with different mechanical resistances. Bead size of 2.2 mm made with 2% alginate and inoculum of 4 × 107 spores/ml gel was determined to be adequate to reduce bead fracture by 32%. The production of endopolygalacturonases (endoPG) was strongly dependent on the temperature alone or in interaction (P < 0.05) with others factors, particularly with the pH of the medium. High temperature (39 °C) increased the production of endoPG 10-fold in comparison with low temperature (27 °C) without modifying the growth of HL (2.2 g/l). Acid pH (2.8) facilitated the production of the enzyme (235 U/(l h−1)), achieving a reduction in growth of 71% in relation to the maximum obtained (3.2 g/l) at pH 4.5. The best endoPG efficiency was found at 39 °C, pH 2.8 using 5 ml of bead volume. Under these conditions, the immobilized cells doubled the production of endoPG in comparison with free cells, and minimum support cell detachment.