Control of Biofilm Formation in Fungi Using Ethanol

Abstract

The adherence of microbial cells onto surfaces often results in a build up of aggregates and formation of what is known as "biofilm". Biofilm formation is the oldest and most powerful forms of life; its strength arises from the microbial cell’s ability to produce layers of extracellular polymeric substance which offers protection against biocides and toxins. Problems arising from biofilm formation are due to the cost associated with losses it causes: the deterioration in plant performance, decrease in the quality and quantity of the product, the damage of the constructing material and the cost for cleaning processes, cost of addition of biocides or labor used to replace or clean the tanks. There are chemical methods for preventing cell adhesion, such as biosurfactant and antibiotics. There are also physical methods which include brushing, scraping and flushing. The attachment process between fungal spores and/or hyphae and substrates is considered a very complex process; it depends mainly on the Summary physicochemical surface interaction, specific molecular factors such as glycoproteins, hydrophobins, carbohydrates and lipids. The aim of the present work is to avoid biofilm formation for an oxidase producing fungus using an eco-friendly method. Twelve fungal isolates were screened, four of which produced intracellular phenol oxidase, the highest producing was the fungus Penicillium purpurogenum, and this fungus produced fungal rings on the container after incubation. Employing types of abiotic stress affected the stress response by the fungus, the changes were observed at pH 5, 30oC and the addition of tryptone to the cultivating media. On the other hand, the use of gamma radiation didn’t result in a consistent change.Therefore, an agro-industrial by-product which is utilized by microorganism as a carbon source, was used as a type of stress to control biofilm formation. Matter of fact, the presence of ethanol increased catalase and lipid peroxidation, while the surface bound protein decreased at the tested ethanol concentration. No changes took place in the surface Summary bound exopolysaccharide (EPS). As for the red pigment secreted by the fungus, the presence of ethanol exhausted the pigment, probably by consuming it for protecting the cells against stress. Combining all types of stress resulted in low biomass; therefore there were no obvious morphological changes in the fungus. The addition of different ethanol concentrations to the growth media showed that 2.5% v/v was un-harming to the fungal growth, concentrations above which, lower fungal growth and/or decrease in spore formation. Following the same trend, 2.5%v/v was also the optimal ethanol concentration which prevented biofilm formation and adhesion on the walls of the container. It also induced the phenol oxidase enzyme.