Biodegradation of Glyphosate by Soil Bacteria: Optimization of Cultivation and the Method for Active Biomass Storage

Conditions for obtaining the active biomass of Ochrobactrum anthropi GPK 3 and Achromobacter sp. Kg 16, bacteria which are able to degrade the herbicide glyphosate (N-phosphonomethylglycine), were investigated. In the batch culture, degradation was most effective in the medium with pH 6.0-7.0 and aeration at 10-60% of air saturation supplemented with glutamate and ammonium chloride as sources of carbon and nitrogen, respectively. Due to the adaptation of the cells and induction of the relevant enzymatic systems, the inoculum grown in the presence of glyphosate exhibited 1.5-2-fold higher efficiency of xenobiotic degradation than that grown with other sources of phosphorus (orthophosphate and methylphosphonic acid). The efficiency of the toxicant decomposition increased with an increase in a specific load of glyphosate, which the cells were subjected to during the initial stage of growth. The specific load was regulated both by the initial cell concentration and the concentration of the phosphorus source, and the effect was probably determined by its availability to microorganisms. Storage of the liquid biopreparation as a paste with stabilizers (ascorbate, thiourea, and glutamate) at room temperature for 50 days resulted in high level of bacteria viability and a degrading activity approximately equal to that obtained when the bacteria were maintained on the agar medium containing glyphosate at 4 degrees C with monthly transfers to the fresh culture medium.