Stereoselective synthesis of stable isotope‐labeled L‐α‐amino acids: Biosynthesis of 2H‐, 13C‐, and 15N‐labeled L‐serines

We have developed a stereospecific biosynthesis of 13C‐ and 15N‐labeled L‐serine which involves the serine‐type methylotroph Methylobacterium extorquens AM1. In this biosynthesis, C‐3 of serine is derived from methanol while C‐2, C‐1 and the α‐amino group are derived from glycine. By starting with the appropriate labeling precursor, we can produce any of the 2H, 13C and/or 15N isotopomers of L‐serine. Using a 5‐L culture, 40–50 millimoles of L‐serine are produced; L‐serine and glycine are recovered from the growth medium and then separated chromatographically.