Characterization of Pleurotus ostreatus Biofilms by Using the Calgary Biofilm Device

The adequacy of the Calgary biofilm device, often referred to as the MBEC system, as a high-throughput approach to the production and subsequent characterization of Pleurotus ostreatus biofilms was assessed. The hydroxyapatite-coating of pegs was necessary to enable biofilm attachment, and the standardization of vegetative inocula ensured a uniform distribution of P. ostreatus biofilms, which is necessary for high-throughput evaluations of several antimicrobials and exposure conditions. Scanning electron microscopy showed surface-associated growth, the occurrence of a complex aggregated growth organized in multilayers or hyphal bundles, and the encasement of hyphae within an extracellular matrix (ECM), the extent of which increased with time. Chemical analyses showed that biofilms differed from free-floating cultures for their higher contents of total sugars (TS) and ECM, with the latter being mainly composed of TS and, to a lesser extent, protein. Confocal laser scanning microscopy analysis of 4-day-old biofilms showed the presence of interspersed interstitial voids and water channels in the mycelial network, the density and compactness of which increased after a 7-day incubation, with the novel occurrence of ECM aggregates with an alpha-glucan moiety. In 4- and 7-day-old biofilms, tolerance to cadmium was increased by factors of 3.2 and 11.1, respectively, compared to coeval free-floating counterparts.