|Peterson, Stephen - Steve|
Submitted to: Research in Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/28/2007
Publication Date: 4/15/2008
Citation: Sera, R., Peterson, S.W., Venancio, A. 2008. Multilocus Sequence Identification of Penicillium Species in Cork Bark During the Manufacture of Wine Bottle Stoppers. Research in Microbiology. 159(3):178-186. Interpretive Summary: The manufacture of cork bottle stoppers suffers losses from molds growing on the cork. We studied the number and types of molds present during the different stages of the manufacturing process. Many of the species were definitively identified using DNA specific techniques. While a variety of odor producing molds were identified, no species known to make the poisonous compound ochractoxin A were found. This study will help the cork industry produce a better quality product while providing information that can help minimize mold related losses.
Technical Abstract: Despite several studies reporting Penicillium as one of the most frequent fungal genera in cork at all the stages of manufacturing stoppers, the isolates were rarely identified to species level. We conducted a detailed study to identify Penicillium species, from the field to the factory environment, prior to and after boiling the cork planks. A total of 84 samples were analyzed for fungi by dilution plating methods and Scanning electron microscopy (SEM) visualization. Of the 486 Penicillium isolates identified based on phenotype, 32 representative strains were selected for identification by multilocus DNA sequence type. A total of 30 species were isolated from cork, including 6 undescribed species. Some field samples were heavily colonized with Penicillium (up to 107 CFU per g of cork) with reproductive structures visible under the SEM in deep layers of the cork. Spores of some species lodged deep in cork can survive the boiling process and P. glabrum, P. glandicola and P. toxicarium, field species with high CFU numbers, are still frequent in cork after boiling. Other field species are killed by the boiling treatment and replaced by ubiquitous competitive Penicillium species originating in the factory environment. Species previously described as capable of producing off odors that contribute to cork taint were isolated at all stages. Nevertheless none of the species isolated was previously described as producer of ochratoxin A, a mycotoxin whose concentration in wine is regulated. Cork proved to be a rich source of novel Penicillium biodiversity.