Rapid analysis of terpenes produced by fermentation using flow injection analysis coupled to APCI MS

Terpenes are an important class of chemicals widely used in consumer and industrial processes. Enzyme- and microorganism-based synthesis is of interest for producing terpenes because of the high selectivity and relatively low environmental impact of these methods compared to other synthetic strategies. Realizing these advantages requires engineering enzymes and microorganisms for good yield of desired products. Such engineering often requires screening hundreds to thousands of genetic variants. High-throughput, label-free screening methods that provide relative quantification and can be readily adapted to new analytes are attractive for decreasing the time required for engineering. We developed a flow injection analysis (FIA) method using atmospheric pressure chemical ionization (APCI) coupled to a quadrupole time-of-flight (Q-TOF) mass spectrometer for detection of terpenes in fermentation mixtures. The method was tested by screening 99 strain variants producing a sesquiterpenoid at 1.3 injections per min with no observable carryover. Comparison of measured concentrations determined by gas chromatography-flame ionization detection (GC-FID) revealed good agreement between the methods with a correlation coefficient of 0.96. However, the GC method required 7 min per injection. Experimental parameters that can be adjusted to improve throughput for the FIA-APCI-MS are also identified.