With a global production volume of above 1 million tons, glyphosate is a broadly used herbicide. At present, the commercial production of glyphosate involves various toxic compounds, reagents and wastes. In recent years, many countries, particularly China, have implemented stricter supervision of production of glyphosate, resulting in its continued price rise. For this reason, there is an urgent need to develop a green approach to the synthesis of glyphosate.
Recently, Gao Jiangtao’s research team from the College of Life Sciences of Fujian Agriculture and Forest University in China published a research paper in Nature Communications entitled, “Harnessing phosphonate antibiotics argolaphos biosynthesis enables a synthetic biology-based green synthesis of glyphosate,” which presents a green glyphosate which is successfully synthesized via synthetic biology.
The team leader of the research team at the earlier stage used genome mining technology to isolate two phosphonic micro molecule antibiotics, argolaphos A and B, from the crude extract of Streptomyces NRRL B-24309. Both compounds lead to a peptide bond formation via AMP and the non-standard amino acid N5-hydroxy-L-arginine, whilst AMP forms the precursor micro molecule for synthesis of glyphosate. The research team has used the heterologous expression and biological method to identify the six structural genes (AlpG-L) required by biosynthesis of AMP, having studied the biosynthesis pathway (Figure 1), which provides a basis for the engineering approach via synthetic biology (Figure 2).
Figure 1 Argolaphos biosynthetic gene cluster
Figure 2 Inorganic phosphate-to-glyphosate workflow via synthetic biology
Later, the research team used the promoter-insulator-RBS technique to improve the AMP yield out of Streptomyces lividans, enabling fermentation concentrations to reach 52 mg/L, which is 500 times greater than the original strain (Figure 3).
Figure 3 Increased AMP yield via promoter-insulator-RBS technique
In addition, the research team has developed an efficient and practical chemical process to convert AMP into glyphosate. The research team tried two synthetic approaches (Figure 4). In the end, it was found that reductive amination in water results in a more efficient synthesis of glyphosate. At room temperature, α-pic-BH3 is used to complete reductive amination 1h of AMP with glyoxylic acid in H2O and AcOH, leading to a glyphosate of higher yield. The same reaction was conducted on a larger scale (1 g), leading to glyphosate of similar yield.
Figure 4 Two approaches to AMP-to-chemical synthesis of glyphosate
To sum up, the research team could finally develop a green alternative for glyphosate production. The co-first authors include Chu Leixia, a doctoral student on the research team of the College of Life Sciences of Fujian Agriculture and Forest University, Luo Xiaoxia, a teacher from Tarim University and Zhu Taoting, a masters student at Fujian Agriculture and Forestry University; corresponding author is Gao Jiangtao, a professor at the College of Life Sciences of Fujian Agriculture and Forest University. The research work was participated in by Deng Zixin, an academician from Shanghai Jiaotong University and Zhang Lili, a teacher at Tarim University.
The research has had sponsorship from the National Natural Science Foundation (31870050), the Synthetic Biology Development Fund of the Ministry of Science and Technology (2021yfa0910502) and the Minjiang Scholarship Program.