Avaliação da formação de biofilmes por fungos filamentosos relevantes em produtos cárneos

Abstract

The ability to form biofilms is considered an evolutionary characteristic for microbial survival. Filamentous fungi that possess this capacity can establish themselves in food processing and maturation environments, thereby acting as a source of contamination. Hence, the effectiveness of sanitation processes is dependent on the sensitivity of these fungi to such conditions. This study evaluated the biofilm formation capacity of filamentous fungi isolated from meat products. Various deteriorating strains (Aspergillus westerdijkiae, Aspergillus ochraceus, Penicillium polonicum, Penicillium nordicum, and Penicillium verrucosum) and starter strains (Penicillium nalgiovense) were tested. Biofilm production by these strains was qualitatively and quantitatively assessed in titration microplates using Czapek yeast extract broth, malt extract broth, and Sabouraud broth as media. Each strain was tested at 1x107 spores/mL concentration and at 25, 20, and 10 °C. The evaluation was conducted in triplicate, with 24, 48, and 72 hours of result readings. Biofilm structures were stained with a 0.5% safranin solution for qualitative evaluation. Quantitative analysis involved measuring the biofilm biomass produced at the optimal incubation time. This was done by extracting the dye with 95% ethanol for 1 minute and then detecting the absorbance using a microplate reader at a wavelength of 530 nm. The results of the qualitative analysis indicated that all strains of A. westerdijkiae and A. ochraceus formed biofilms, while most strains of Penicillium did not demonstrate the same capacity under the evaluated conditions. The three tested media were found suitable, although differences in intensity were observed in certain situations. In the quantitative evaluation, absorbance analysis revealed positive biomass formation capacity for all Aspergillus strains analyzed at 25 and 20 °C, although this capacity decreased at 10 °C. For the Penicillium species, the overall capacity was very low, with P. polonicum strains showing slight formation under certain conditions, while the other species did not exhibit this capacity. Our findings lead us to conclude that strains of A. westerdijkiae and A. ochraceus isolated from deteriorated meat products are strong biofilm formers, unlike the deteriorating strains P. nordicum, P. verrucosum, and the biotechnological P. nalgiovense. Further studies are needed to elucidate the impact of biofilms on fungal tolerance to preservatives and disinfectants.