Effect of Non-Equilibrium Plasma on Microorganisms Colonizing Diatomaceous Earth after the Beer Filtration Process

Abstract

The present study evaluates the antimicrobial potential of non-equilibrium plasma against microorganisms isolated from diatomaceous earth, which is a waste product from the beer filtration process. For evaluation, waste diatomaceous earth from an industrial brewery was treated with non-equilibrium plasma using a glidearc reactor. The temperature of the treated samples was monitored. The effect of plasma on the morphology of the treated material was investigated microscopically. Plasma can affect the treated material in various ways and change its physicochemical properties. Consequently, the scope of potential plasma applications is constantly expanding from material technologies to decontamination applications in the food industry, environmental protection and medicine and stimulates activities in, for example, agriculture and medicine. At the same time, microbiological analyzes were carried out to determine the presence of selected groups of microorganisms on diatomaceous earth before and after plasma treatment. The study revealed that the porous structure of diatomaceous earth is not an obstacle to the effective removal of microorganisms from it using plasma. A significant decrease in the amount of both bacteria and yeast relative to the control (non-plasma samples) was observed with the increasing contact time of the diatomaceous earth with the plasma. The numbers of bacteria and yeast decreased by a maximum of 2.2 log10 CFU∙g−1 and 1.72 log10 CFU∙g−1 (30 min of plasma contact), respectively. The obtained results are extremely promising and encourage further, in-depth research to optimize the plasma process and its effect on microorganisms.