Viability of yeasts after exposure to flax-fiber based composite materials

Abstract

Abstract In the present study, the prepared bio-composite materials based on flax fibers containing caffeine or nano-copper (Cu) or corundum (Al2O3) as a potential biocidal substance were prepared and tested on their toxicity. Two viability tests were performed. Firstly, the screening test based on colouring by Methyl-blue was applied on yeast cells of strain Saccharomyces cerevisae. The number of cells density was observed under microscope and Methyl-blue was then added. Part of the cells coloured in blue and it indicated their death. For this reason, MTT viability assay was performed. The method is based on production of blue product formazan by yeasts after their metabolization of added initial substrate, 3-[4,5-dimethylthiazol-2-yl]-2,5-difenyltetrazolium bromide. The intensity of blue-coloured formazan was measured spectrophotometrically at 485 nm. The results indicated that the inhibition of yeasts was increased in the following rate: cu-samples (14-16 %) < flax sample without biocidal substances (21%) = pure flax (23 %) < caffeine-samples (up to 29 %) < corundum-samples (up to 35 %).