Development of a novel quantitative PCR assay as a measurement for the presence of geosmin-producing fungi

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To provide an efficient technique for monitoring the off-flavoured fungal compound geosmin.

Methods and Results:

Geosmin-associated gpe1 gene of Penicillium expansum displayed ≥99% similarity to cytochrome P450 gene of geosmin-producing P. restrictum, but ≤40% similarities to geosmin biosynthesis, non-cytochromic gene of Streptomyces avermitilis and cytochrome P450 genes of non-geosmin-producing Neotyphodium lolii, Phoma betae and P. paxilli. Serial 10-fold dilutions of P. expansum's DNA was subjected to a previously reported qPCR assay (Atoui et al. 2007), utilizing gpe1 specific primer pair ‘SNgpe1F/SNgpe1R’. A linear relationship between DNA quantity and Cycle Threshold (Ct), with strong correlative coefficient, was observed. Using the available physico-chemical method, geosmin was quantified in 188 grape samples. Penicillium spp's DNA was quantified in these samples, utilizing the developed qPCR assay. A strong positive correlation (R2 = 0·97) between Penicillium's DNA and geosmin concentration was observed. Furthermore, <50 ng μl−1Penicillium's DNA corresponds to geosmin level below the permitted intensity limit i.e. 4, for ‘Flavour Profile Analysis’.


Penicillium spp., genomic DNA level can provide an efficient way to quantify geosmin.

Significance and Impact of the Study:

This particular qPCR technique can be utilized in numerous food industries, for the timely detection and monitoring of geosmin contamination.

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