Multi-capillary Column Ion Mobility Spectrometry of Volatile Metabolites for Phenotyping of Microorganisms

Abstract

Rational strain engineering requires solid testing of phenotypes including productivity and ideally contributes thereby directly to our understanding of the genotype-phenotype relationship. Actually, the test step of the strain engineering cycle becomes the limiting step, as ever advancing tools for generating genetic diversity exist. Here, we briefly define the challenge one faces in quantifying phenotypes and summarize existing analytical techniques that partially overcome this challenge. We argue that the evolution of volatile metabolites can be used as proxy for cellular metabolism. In the simplest case, the product of interest is a volatile (e.g., from bulk alcohols to special fragrances) that is directly quantified over time. But also nonvolatile products (e.g., from bulk long-chain fatty acids to natural products) require major flux rerouting that result potentially in altered volatile production. While alternative techniques for volatile determination exist, rather few can be envisaged for medium to high-throughput analysis required for phenotype testing. Here, we contribute a detailed protocol for an ion mobility spectrometry (IMS) analysis that allows volatile metabolite quantification down to the ppb range. The sensitivity can be exploited for small-scale fermentation monitoring. The insights shared might contribute to a more frequent use of IMS in biotechnology, while the experimental aspects are of general use for researchers interested in volatile monitoring.

A rapid liquid chromatography‐electrospray ionization‐ion mobility spectrometry method for monitoring nine representative metabolites in the seedlings of cucumber and wheat

“…Under atmospheric conditions of IMS, different migration rates of gas‐phase ions pass through a weak electric field to achieve separation and detection [15, 16]. Recently, the incorporation of an ESI source into IMS has broadened its applications, so far covering biological medicine [17–19], food safety [20], agriculture [21, 22], and environmental pollution [23–26]. When combined with HPLC separation, the ESI‐IMS system can be used for both orthogonal separation and characterization of chemicals.…”

Biogenic Volatile Compounds for Plant Disease Diagnosis and Health Improvement

“…, 2016 ): and can act as inter- and intra-species signals in plants ( Yi et al, 2009 ), and therefore have potential as novel pesticides. In recent years, biogenic volatiles have been exploited to modulate plant physiology ( Sharifi and Ryu, 2016 ; Song et al, 2015 ), to detect diseased or stressed plants ( Jansen et al, 2011 ; Niinemets et al, 2013 ), and to discriminate between bacterial species ( Halbfeld et al, 2018 ; Lough et al, 2017 ; Spinelli et al, 2012 ; Wilson et al, 2004 ).…”