8. Biological Limitations on Glyphosate Biodegradation

Glyphosate is currently considered the most important herbicide of the world due to its broad-spectrum activity, effectiveness, and loss of global patent protection. Its ubiquitous presence in the environment due to anthropogenic activities and recalcitrance has the potential to affect animal behavior and interfere with ecological processes. Despite its important role in the protection of crops, it is important to establish strategies to reduce potential human exposure or decrease its presence in the environment. To date, only one microbial enzyme known as C-P lyase is acknowledged to drive complete glyphosate mineralization. AMPA, the common metabolite product of glyphosate biodegradation, still possesses the unique C-P bond of phosphonates and retains it toxic profile and recalcitrance. Thus, it is important to consider glyphosate and AMPA biodegradation altogether. Nevertheless, the potential to develop a bioremediation process is mainly limited by the genetic regulatory system that governs the expression of the C-P lyase, as it strongly depends on low environmental levels of phosphate. Thus, the complete mineralization of this herbicide by the sole use of microorganisms would remain insufficient until (1) more research on additional genetic control mechanisms of C-P lyase expression are explored, (2) alternative enzymes are studied in detailed, or (3) more complex and elaborated processes are considered. This work explores the available information on glyphosate biodegradation over the course of 40 years of study, the different pathways involving the C-P lyase, the genetic and physiological regulatory system that governs these processes, and the factors limiting the development of glyphosate bioremediation technologies.