Characterization of detergent-stable proteases isolated from Citrus sinensis fruit peel

Saheed Ibraheem, Sylvia Malomo, Adedoyin Igunnu


Proteases are important group of enzymes with wide industrial applications including laundry. They have been isolated and characterized from different agro wastes but the use of Citrus sinensis fruit peel as a source of protease has not been reported.  In this study, low molecular weight (10-17 kDa) proteases were purified and characterized from C. sinensis fruit peel using a combination of ammonium sulphate precipitation, dialysis and sephadex G150 column chromatography. One unit of protease activity was defined as the amount of the enzyme required to liberate one microgramme (1 μg) of tyrosine from gelatin per minute at 37°C under standard assay conditions. The elution profile obtained from gel filtration chromatography depicted three peaks of protease activity designated as proteases I, II and III. The purification fold obtained for ammonium sulphate precipitation, dialysis and Proteases I, II and III fractions were 1.7, 3.85, 9.47, 9.84 and 8.47 respectively. The activities of Proteases I and II were significantly increased (p<0.5) in the presence of 5-10 % w/v, and 1-10 v/v % Tween 80 respectively. However, the activity of Protease III was not significantly affected (p>0.5) by Tween 80. Triton-X significantly increased (p<0.5) Protease II activity at 5 to 10% v/v concentrations but did not significantly affect (p>0.5) the activities of Proteases I and III between 1 to 10% v/v concentrations. SDS significantly increased (p<0.5) the activities of proteases I and II at 5-10 % w/v, and 1-10 w/v % respectively but did not significantly affect (p>0.5) Protease III activity. Findings from this study suggest that proteases from C. sinensis fruit peel are detergent stable which may be useful in laundry industries.

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