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. 2019 Apr 4;24(7):1333.
doi: 10.3390/molecules24071333.

Effects of pH and Cultivation Time on the Formation of Styrene and Volatile Compounds by Penicillium expansum

Hye Won Kim  1 , Sang Mi Lee  2 , Jeong-Ah Seo  3 , Young-Suk Kim  4
Affiliations

Effects of pH and Cultivation Time on the Formation of Styrene and Volatile Compounds by Penicillium expansum

Hye Won Kim et al. Molecules. .

Abstract

Styrene can be formed by the microbial metabolism of bacteria and fungi. In our previous study, styrene was determined as a spoilage marker of Fuji apples decayed by Penicillium expansum, which is responsible for postharvest diseases. In the present study, P. expansum was cultivated in potato dextrose broth added with phenylalanine-which is a precursor of styrene-using different initial pH values and cultivation times. Volatile compounds were extracted and analyzed using gas chromatography-mass spectrometry (GC-MS) combined with stir-bar sorptive extraction. The 76 detected volatile compounds included 3-methylbutan-1-ol, 3-methyl butanal, oct-1-en-3-ol, geosmin, nonanal, hexanal, and γ-decalactone. In particular, the formation of 10 volatile compounds derived from phenylalanine (including styrene and 2-phenylethanol) showed different patterns according to pH and the cultivation time. Partial least square-discriminant analysis (PLS-DA) plots indicated that the volatile compounds were affected more by pH than by the cultivation time. These results indicated that an acidic pH enhances the formation of styrene and that pH could be a critical factor in the production of styrene by P. expansum. This is the first study to analyze volatile compounds produced by P. expansum according to pH and cultivation time and to determine their effects on the formation of styrene.

Keywords: Penicillium expansum; cultivation time; pH; phenylalanine metabolism; styrene; volatile compounds.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
The contents of volatile compounds derived from phenylalanine at different pH and cultivation times and their possible pathways in P. expansum. Notes: All values are mean values of relative peak area to that of internal standard ± standard deviation from three replicates. PAL—phenylalanine ammonia lyase, CADC—cinnamic acid decarboxylase, PAR—phenyl acetaldehyde reductase, CCMT—cinnamic acid carboxyl methyl transferase, AAD—aryl-aldehyde dehydrogenase. Error bars represent standard deviation of three replicates.
Figure 2
Figure 2
Partial least square-discriminant analysis (PLS-DA) score plot of volatile compounds produced by P. expansum according to pH and cultivation time.
See this image and copyright information in PMC

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