Abstract
Volatile hydrocarbon production by Ascocoryne sacroides was studied over its growth cycle. Gas-phase compounds were measured continuously with a proton transfer reaction-mass spectrometry (PTR-MS) and at distinct time points with gas chromatography-mass spectrometry (GC-MS) using head space solid phase microextraction (SPME). The PTR-MS ion signal permitted temporal resolution of the volatile production while the SPME results revealed distinct compound identities. The quantitative PTR-MS results showed the volatile production was dominated by ethanol and acetaldehyde, while the concentration of the remainder of volatiles consistently reached 2,000 ppbv. The measurement of alcohols from the fungal culture by the two techniques correlated well. Notable compounds of fuel interest included nonanal, 1-octen-3-ol, 1-butanol, 3-methyl- and benzaldehyde. Abiotic comparison of the two techniques demonstrated SPME fiber bias toward higher molecular weight compounds, making quantitative efforts with SPME impractical. Together, PTR-MS and SPME GC-MS were shown as valuable tools for characterizing volatile fuel compound production from microbiological sources.
Highlights
Ascocoryne sarcoides is an endophytic fungus recently isolated from Northern Patagonia and has the potential to produce a petroleum-like fuel (Mycodiesel®) directly from a cellulose fermentation process [Strobel, Knighton, Kluck, Ren, Livinghouse, Griffin, Spakowicz and Sears 2008]
The Henry’s Law constants calculated from the PTR data are consistent with those reported previously in the literature (Table 1), which indicates that the ions monitored are free from any interferences and the response of the proton transfer reaction-mass spectrometry (PTR-MS) is within the linear dynamic range of the instrument
The PTR-MS and solid phase microextraction (SPME) agree on the identification of the standard compounds with the exception of ethanol which was not detected by the SPME
Summary
Ascocoryne sarcoides is an endophytic fungus recently isolated from Northern Patagonia and has the potential to produce a petroleum-like fuel (Mycodiesel®) directly from a cellulose fermentation process [Strobel, Knighton, Kluck, Ren, Livinghouse, Griffin, Spakowicz and Sears 2008]. Ascocoryne sarcoides (NRRL 50072) has been reported to produce a series of straight chained and branched medium chain-length hydrocarbons of C5-C10 chain length, in the range of gasoline fuel, including. Recent studies have identified a variety of compounds produced by A. sarcoides on different media using headspace GC-MS on discrete solid phase microextraction (SPME) fiber samples [Griffin, Spakowicz, Gianoulis and Strobel 2010; Strobel et al 2008]. The SPME technique was introduced in the 1990’s [Arthur and Pawliszyn 1990], and SPME fibers have been used to identify and quantify complex volatile mixtures including hydrocarbons from water, soil, food and wine [Langenfeld et al 1996; Mallouchos et al 2002; Parkerton et al 2000; Robinson et al 2011]. Several studies have revealed instabilities with quantification by this method [Brás et al 2011; Weldegergis et al 2011; Zeng and Noblet 2002], so further evaluation of the quantitative use of the method for volatile mixtures from A. sarcoides was tested
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