Proteolytic activity of wild fruits of Bromelia karatas L. of Yucatán, Mexico

Introduction: Bromeliads are a source of proteases that have not been fully studied. Objectives: To evaluate the proteolytic activity of wild fruits of Bromelia karatas L. under different temperature, pH and NaCl conditions, and to estimate the thermal stability of their proteases. Materials and methods: The effect of pH (6, 7, 8, 9, 10 and 12), incubation temperatures (30, 40, 50, 60 and 70 degrees C) and NaCl concentrations (5, 10 and 20 %) on the proteolytic activity of the fruits was compared. The thermal stability of the proteases was assessed at 30, 50 and 70 degrees C for 240 minutes. The molecular weights and isoelectric points of the proteases were estimated by non-reducing two-dimensional zymography. The data were analyzed using a one-factor ANOVA and Tukey's test (alpha = 0.05). Results and discussion: The proteolytic activity of B. karatas fruit extract (8.59 U.mg(-1)) was greater than that of Ananas comosus (L.) Merr. variety comosus (3.42 U.mg(-1)). The activity was higher at pH 6 and 7 and in concentrations lower than 5 % NaCl. Proteases were stable at 30 and 50 degrees C for 210 minutes. The two-dimensional zymogram, under non-reducing conditions, showed at least 40 light zones with apparent molecular weights between 27.3 and 290 kDa, potentially representing proteases. Conclusion: The proteases of B. karatas have potential for application in the food industry.