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Fungal extracellular enzymes may play a role in biodeterioration of dried materials of medicinal plants and in propagation of toxigenic and pathogenic fungal strains. However, no data on enzymatic activities of xerophilic fungi contaminating these materials have been found in the literature. The objective of the study was to determine extracellular enzyme profiles of slow-growing fungi, i.e. Eurotium amstelodami, E. chevalieri, E. herbariorum and Aspergillus versicolor isolated from dried materials of medicinal plants from herbal shops of Szczecin, Poland. Solid media and API ZYM® test were used to determine enzymatic activities. The highest colony diameters were observed in A. versicolor on gelatin, cellulose, tributyrin, rapeseed oil, biodiesel oil and diesel oil agars, and in E. herbariorum on milk and starch agars. A. versicolor also showed the highest hydrolytic activity on milk, gelatin, starch and tributyrin agars. No hydrolysis zones were formed on cellulose, rapeseed oil and biodiesel oil agars, but the stimulation effect of the oils on fungal growth was clearly observed. The effect was the highest in E. amstelodami, and considerably increased during a 21-day incubation period. In addition, E. amstelodami and A. versicolor showed high catalase, urease and DNA-se activities. A. versicolor had higher pectate lyase activity compared to E. amstelodami. Of the fungi examined, E. amstelodami showed the highest hydrolase activity in the API ZYM® test. A. versicolor and E. amstelodami were found to be the two species with the highest biodeterioration potential for dried materials of medicinal plants. Xerophilic fungi isolated from this environment could also be used in bioremediation.
The contamination of dried medicinal plants with microscopic fungi has been the subject of many studies. However, no data on extracellular enzyme activities of xerophilic fungi contaminating the plants have been found in the literature. Therefore, the objective of our study was to determine extracellular enzyme profiles of fast-growing xerophilic fungi, i.e. Aspergillus flavus, A. fumigatus, A. melleus, A. nidulans, A. niger, A. parasiticus and Trichothecium roseum isolated from dried medicinal plants from herbal shops in Szczecin, Poland. Solid media and the API ZYM® test were used for measuring enzyme activities. Among the fungi, A. melleus had the highest hydrolytic activity on milk, gelatin, starch, tributyrin, rapeseed oil and biodiesel oil agars, while A. fumigatus showed extremely high stimulation index values on rapeseed oil and biodiesel oil agars. The stimulation index increased during a 5-day incubation period. In the API ZYM® test A. nidulans showed the highest hydrolase activity. Among the hydrolases, ß-glucosidase activity was the highest, followed by acid phosphatase, N-acetyl-ß-glucosaminidase and naphthol-AS-BI-phosphohydrolase activities. The fungi contaminating dried medicinal plants are able to utilize a number of substrates and, therefore, possess high biodeterioration potential. Due to the ability to degrade hydrocarbons, fungal isolates from dried medicinal plants can be used for biotechnological purposes, e.g. in air biofiltration and waste or soil bioremediation.
Fifty samples from five baby food products mainly made of cereal flour(s) were analyzed. The moisture contents of these products were between 11.14% and 11.9%, a level below 14.0%, the recommended level for safe storage of cereal grains and their products. The mycological analysis was carried out using the dilution plate method and two isolation media (DG18 for isolation of xerophilic fungi and DRBC for fungi in general). A total of 80 species related to 37 genera in addition to some unidentified fungal and yeast species were recorded on both media from the five products. The products were contaminated abundantly by xerophilic fungi which were occurring in 88% of food samples and accounting for 18.1% of the total CFU as recorded on DG18. The highest contamination level by xerophiles was registered in Mwebaza rice porridge (a component of rice flour) and the lowest in Mukuza (a product of maize, soyabean and sorghum flours). 11 xerophilic species were recorded of which Aspergillus and Eurotium (4 species each) were the predominant giving rise to 9.1% and 8.9% of the total CFU, with A. wentii, A. candidus, E. cristatum and E. repens were the most contaminating species. Of the fungi recorded other than xerophiles, species of Aspergillus (particularly A. flavus followed by A. niger), Penicillium (P. citrinum, P. oxalicum), Fusarium (F. solani, F. tricinctum), Cladosporium (C. sphaerospermum) and yeasts were the most predominant. Contamination of such foods is a matter of health hazard as these foods are for babies. So, the use of fresh, well-dried and uncontaminated flours for production of such foods is recommended.
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