Detoxification mechanism of organophosphorus pesticide via carboxylestrase pathway that triggers de novo TAG biosynthesis in oleaginous microalgae

Abstract

Organophosphorus compounds exhibit a wide range of toxicity to mammals. In this study the effect of malathion on the growth and biochemical parameters of microalgae was evaluated. Three microalgae (Micractinium pusillum UUIND2, Chlorella singulari UUIND5 and Chlorella sorokiniana UUIND6) were used in this study. Among the three algal strains tested, Chlorella sorokiniana UUIND6 was able to tolerate 100 ppm of malathion. The photosynthetic pigments, the protein, carbohydrate and lipid contents of microalgal cells were also analyzed. About 90% degradation was recorded in 25 ppm, 50 ppm and 70% was recorded in 100 ppm of malathion by Chlorella sorokiniana. A mechanism of degradation of malathion by Chlorella sorokiniana is proposed in this study. Activity of carboxylesterase was increased in algal cells cultivated in malathion containing medium which confirmed that malathion degraded into phosphate. Increased amount of Malondialdehye (MDA) indicate the development of free radicals under the stress of malathion which substantialy increase de novo TAG biosynthesis, while increased level of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) suggested their association in scavenging of free radical.

Keywords: Biodegradation; Carboxylesterase; De novo TAG; Lipid; Organophosphorus.