Rapid total volatile organic carbon quantification from microbial fermentation using a platinum catalyst and proton transfer reaction-mass spectrometry.

Heidi R Schoen,W Berk Knighton,Brent M Peyton

doi:10.1186/s13568-016-0264-2

Heidi R Schoen, W Berk Knighton + Show 1 more

Open Access

https://doi.org/10.1186/s13568-016-0264-2

Copy DOI

Journal: AMB Express	Publication Date: Oct 5, 2016
Citations: 7	License type: CC BY 4.0

Affiliation: Montana State University

Abstract

A novel analytical system was developed to rapidly and accurately quantify total volatile organic compound (VOC) production from microbial reactor systems using a platinum catalyst and a sensitive CO2 detector. This system allows nearly instantaneous determination of total VOC production by utilizing a platinum catalyst to completely and quantitatively oxidize headspace VOCs to CO2 in coordination with a CO2 detector. Measurement of respiratory CO2 by bypassing the catalyst allowed the total VOC content to be determined from the difference in the two signals. To the best of our knowledge, this is the first instance of a platinum catalyst and CO2 detector being used to quantify the total VOCs produced by a complex bioreactor system. Continuous recording of these CO2 data provided a record of respiration and total VOC production throughout the experiments. Proton transfer reaction-mass spectrometry (PTR-MS) was used to identify and quantify major VOCs. The sum of the individual compounds measured by PTR-MS can be compared to the total VOCs quantified by the platinum catalyst to identify potential differences in detection, identification and calibration. PTR-MS measurements accounted on average for 94 % of the total VOC carbon detected by the platinum catalyst and CO2 detector. In a model system, a VOC producing endophytic fungus Nodulisporium isolate TI-13 was grown in a solid state reactor utilizing the agricultural byproduct beet pulp as a substrate. Temporal changes in production of major volatile compounds (ethanol, methanol, acetaldehyde, terpenes, and terpenoids) were quantified by PTR-MS and compared to the total VOC measurements taken with the platinum catalyst and CO2 detector. This analytical system provided fast, consistent data for evaluating VOC production in the nonhomogeneous solid state reactor system.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0264-2) contains supplementary material, which is available to authorized users.

Highlights

Fungi and bacteria produce hundreds of volatile organic compounds (VOCs) with industrial applications including biofuels, insecticides, quorum sensing and biocontrol, flavor and aroma compounds, antibacterials and antifungals (Hung et al 2015; Kai et al 2009; Morath et al.2012; Strobel 2014)
The area under the VOC production curve can be integrated to find the total amount of VOCs produced during the experiment in parts per million carbon (ppm C), which can be converted to the mass of carbon using the flow rate, temperature and pressure of the system
The combination of Proton transfer reaction-mass spectrometry (PTR-MS), platinum catalyst and sensitive CO2 detector allowed for real-time VOC sampling with a quantitative determination of the compounds produced

Summary

Introduction

Fungi and bacteria produce hundreds of volatile organic compounds (VOCs) with industrial applications including biofuels, insecticides, quorum sensing and biocontrol, flavor and aroma compounds, antibacterials and antifungals (Hung et al 2015; Kai et al 2009; Morath et al.2012; Strobel 2014). Bioprospecting has identified many new microorganisms that produce valuable VOCs, and the types and amounts of these compounds often change with substrate, culturing conditions and growth phase (Bunge et al 2008; Kai et al 2009; Morath et al 2012; Strobel 2014). Extraction techniques may identify fewer VOCs than SPME GC–MS (Kai et al 2009; Morath et al 2012) Another analytical method, proton nuclear magnetic resonance can quantify VOCs quickly, but has poor sensitivity, cannot determine carbon length and some oxygenated VOCs cannot be measured because signals are confounded with sugar peaks (Mallette et al 2014)

Methods

Results

Conclusion