Screening of Aspergillus species for occurrence of lectins and their characterization

Out of 15 Penicillium species screened for lectin activities, P. griseofulvum and P. thomii were found to possess mycelial lectin activity. None of the species displayed extracellular or cell surface-bound lectin activity. Both species agglutinated rabbit erythrocytes. P. griseofulvum lectin showed specificity to human type O erythrocytes. While P. thomii lectin specifically agglutinated human type A erythrocytes. Highest lectin activities from P. thomii and P. griseofulvum were expressed after 8 and 7 days of growth, respectively. Lectins from both the species displayed a high binding affinity to chondroitin-6-sulphate, mucin, asialofetuin, D-sucrose, and D-trehalose. Ammonium sulphate at 50% saturation yielded 80% of the total lectin activity. Dialysis and ultrafiltration of the precipitates resulted in 1.79 and 3.46 fold purification of P. griseofulvum and P. thomii lectins, respectively. Both lectins showed pH optima between 7.0-8.0 and were stable near the neutral pH after 2 h. P. thomii lectin exhibited optimal activity at 35-40 degrees C, and P. griseofulvum lectin at 30-40 degrees C. P. thomii lectin showed a complete loss of activity above 40 degrees C, P. griseofulvum lectin was stable at or below 35 degrees C.