Catalytic hydrolysis of microcystin-LR peptides on the surface of naturally occurring minerals

Abstract

There are increasing concerns about detoxification of microcystin-LR (MC-LR) over the past few decades. Nevertheless, the removal of MC-LR in water by hydrolysis has not been addressed yet. The hydrolysis efficiencies of MC-LR by six natural minerals were investigated in the present study. Limonite displayed the highest activity among the screened six minerals, which is in accordance with the highest specific surface area (17.8 m2/g) and surface acidity. The hydrolysis of MC-LR was catalyzed by Lewis acid sites on limonite surface. The effects of temperature, pH reaction time and illumination on MC-LR hydrolysis catalyzed by limonite were then investigated. As expected, the high temperature, the addition of either acid or base and long reaction time could enhance the reaction rate, but UV light irradiation had little influence. These results give the indication that naturally occurring minerals can promote the hydrolysis of MC-LR, which gives a more universal view about the natural degradation of microcystins and could lead to more accurate predictions of the duration of microcystin toxicity in environment.