Measurement of the 15N/14N ratio of phenylalanine in fermentation matrix by isotope ratio mass spectrometry

Objectives To determine the origin of 15N-labeled phenylalanine in microbial metabolic flux analysis using 15N as a tracer, a method for measuring phenylalanine δ15N using HPLC coupled with elemental analysis-isotope ratio mass spectrometry (EA-IRMS) was developed.