Enhanced biodegradation of glyphosate by Chlorella sorokiniana engineered with exogenous purple acid phosphatase

Abstract

Organophosphate pesticides, particularly glyphosate, persist in aquatic environments due to widespread agricultural usage, posing substantial environmental and health risks. This study explores the bioremediation potential of genetically engineered Chlorella sorokiniana, expressing purple acid phosphatase (PAP) from Phaeodactylum tricornutum, for glyphosate biodegradation. The engineered strain (OE line) demonstrated complete glyphosate biodegradation at concentrations below 10 ppm within 4-6 days, surpassing the wild type (WT). Enhanced biodegradation in the OE line was attributed to increased growth and ATP levels due to the release of inorganic phosphate, indicating enhanced metabolic efficiency. Photosynthetic parameters, as well as chlorophyll, and carotenoid contents, were significantly improved, driving higher biomass accumulation. Metabolic shifts toward lipogenesis were observed, supported by the upregulation of triacylglycerol-related genes. Additionally, antioxidant enzyme activities (GPx, SOD, CAT) were elevated in the OE line, mitigating oxidative stress. Importantly, the overexpression of PAP activated and upregulated the level of endogenous CsPAP18, which displayed stable binding with glyphosate and its metabolite aminomethylphosphonic acid, highlighting the synergistic role of PAP and CsPAP18 in glyphosate biodegradation. The OE line effectively treated glyphosate-contaminated real wastewater, confirming the feasibility of engineered strain for environmental remediation. This study provides valuable insights into the potential of engineered microalgae for effective and sustainable wastewater treatment, specifically targeting the removal of organophosphate contaminants in freshwater environments.

Keywords: Bioremediation; Chlorella sorokiniana; Glyphosate; Purple acid phosphatase; Wastewater treatment.