STUDY OF INHIBITION OF YEASTS, LACTIC AND ACETIC BACTERIA USING SILVER PARTICLES

This paper deals with a study of the inhibition of microorganisms occurring in grape must and wine, using silver in the form of nanoparticles and colloidal solution. Pure cultures of yeasts Saccharomyces cerevisiae and Brettanomyces bruxellensis, lactic acid bacteria Lactobacillus brevis, Pediococcus damnsosus and acetic acid bacteria Acetobacter aceti and Gluconobacter oxydans were used for the experiments. Attention was primarily focused on monitoring changes in carbohydrate processing, namely glucose, fructose, sucrose, maltose, mannitol, galactose, trehalose, and ß-glucosidase activity. These biochemical determinations have shown limitations in carbohydrate processing, particularly sucrose in yeasts, and fructose, glucose and sucrose in bacteria. The effects of silver have also been observed in natural microflora found in grape must from Chardonnay and Hibernal. Colloidal silver at concentrations 40, 70 and 100 ppm and silver nanoparticles at concentrations 70, 150 and 250 ppm were used for inhibition. A plate method was used to determine the number of viable colonies. With an increasing concentration of applied substances, the growth of both yeasts and bacteria was strongly inhibited, as indicated by the numbers of colonies cultivated from the must. Yeast growth was inhibited by the lowest concentration ­– (70 ppm) by up to 72% and bacterial growth by up to 75.5%.