Kinetic study of glyphosate biodegradation by actinobacterial consortium RH1: implications for bioremediation

The excessive use of glyphosate herbicide in agriculture adversely affects the environment and soil health. Bioremediation using microbial consortia offers an efficient approach for transforming pesticides into less harmful products.

The study investigated glyphosate biodegradation by the RH1 consortium and identified suitable kinetic models to support bioremediation.

Glyphosate biodegradation was investigated at concentrations of 1-200 mg/L using the RH1 microbial consortium comprising four Streptomyces strains (SPA2, IT, Herb, and SC). These strains had been previously isolated and validated for their individual glyphosate-degrading capacity. Consortium activity was assessed under optimized conditions (30 °C, pH 7.2, and 4% inoculum). Degradation kinetics were modeled using several established approaches, including Haldane-Andrews, Yano and Koga, Tseng and Wayman, and Webb. Comparative functional analysis was further performed at 50 mg/L using total organic carbon (TOC) quantification and ATR-FTIR spectroscopy to distinguish consortium performance relative to single-strain treatments.

Following 15 days of incubation under optimized conditions, the RH1 consortium achieved high glyphosate removal efficiencies of 92.2%, 87.2%, 91.72%, 92.06%, 54.11%, and 37.085% at initial concentrations of 1, 10, 25, 50, 100, and 200 mg/L, respectively. Notably, at 50 mg/L the consortium demonstrated the highest degradation rate compared with pure-culture treatments. Kinetic evaluation indicated that the Haldane-Andrews model best described the degradation behavior (F = 65.49, P = 0.00074, R ² = 0.976). At the same concentration (50 mg/L), total organic carbon (TOC) decreased by 91.03%, corroborating substantial mineralization or conversion of organic constituents. ATR-FTIR spectroscopy further confirmed glyphosate transformation by showing alterations in the pesticide's chemical bonding patterns after biodegradation, consistent with structural modification of the molecule.

The RH1 actinobacterial consortium efficiently degraded glyphosate, fitting best to the Haldane-Andrews kinetic model. Significant TOC reduction and ATR-FTIR-confirmed structural changes indicate effective glyphosate transformation, highlighting RH1's potential for bioremediation of glyphosate-contaminated soils.