Studies on the bioremediation potential of glyphosate by the green saltwater microalgae Chlorella vulgaris

Glyphosate (N-(phosphonomethyl)-glycine) C3H8NO5P is a major ingredient in various herbicides used in global agricultural practices. However, the financial benefits of its application come with concerns for human health and ecological preservation, highlighting the necessity to quantify and monitor glyphosate pollution. In this study we improved a protocol for residual glyphosate quantification in alkaline media based on the reaction between glyphosate and chromogenic reagent ninhydrin when exposed to a solution of sodium molybdate at 85-95°C, which produces a Ruhemann’s purple product with a VIS maximum absorption at a wavelength of 570nm. Furthermore, we screened green saltwater microalgae Chlorella vulgaris as a bioremediation agent using an acute toxicity test, concentration gradient exposure, and by measuring its ability to remove glyphosate from BG11 liquid media. The glyphosate calibration curve was linear for aliquots ranging at 2.5-20mg/L with a correlation coefficient of 0.991 and a limit of detection and quantification of 0.057mg/L and 0.191mg/L, respectively. C. vulgaris grew in BG11 medium with glyphosate concentrations ≤ 7.50mg/L, while the Lethal Dosage 50% value was estimated at 3.97mg/L with a 95% confidence interval. Finally, our findings demonstrated that C. vulgaris successfully reduced glyphosate concentrations from an alkaline medium by 47.71% within a period of eight days. Our findings indicate that while C. vulgaris couldn’t decrease glyphosate concentrations to EPA standards of 0.7mg/L, it does show potential as a bioremediation agent. Thus, further research is required towards its real-world application.