The impact of the duration of wave treatment on the development of yeast populations

Abstract

Introduction: The scientific literature does not contain research on the influence of monochromatic light treatment on the development of bottom-fermenting beer yeast populations.Purpose: An analysis of the literature data allowed us to suppose the possibility of activating the development of the beer yeast Saccharomyces cerevisiae population through preliminary treatment with light of visible spectrum wavelengths, providing technological and economic efficiency of such an impact method on a production scale.Materials and Methods: The object of research was the process of cultivating a population of bottom-fermenting beer yeast Saflager S-189 (Fermentis). The subject was the influence of preliminary treatment of the seed yeast with monochromatic light with a wavelength of 980 nm on this process. Its effectiveness was assessed by the weight loss of the cultivation medium, the increase in the total cell titre, the proportion of unviable and "fed" cells. A KFK-2 photoelectrocolorimeter was used as a source of monochromatic light with wavelengths of the visible range. Seeding of mediums and sample preparation for analysis were performed in a BAVnp-01-"Laminar-S."-1.2 antibacterial air medium box. The yeast's fermenting activity was assessed by the weight loss of the nutrient medium; the total cell titre was established by counting in a Goryaev's chamber; the percentage of unviable cells was determined using methylene blue dye; the percentage of "fed" yeast cells was established by staining glycogen with iodine solution.Results: Preliminary treatment of the seed yeast with monochromatic light (980 nm) allowed increasing the fermenting activity of bottom-fermenting beer yeast by 10-15% compared to the control, which is consistent with the results of other research groups concerning populations of microorganisms of other genera and species. The values of other determined indicators - the proportion of "fed" and unviable cells, the total yeast cell titre - in the experimental variants were at the level of those in the control samples or slightly inferior to them. Data on the influence of the duration of seed yeast irradiation for 60, 120 or 180 minutes on the listed controlled indicators are presented, and the authors express the opinion about the appropriateness of its conduction for 60 minutes.Conclusion: The principle possibility of activating the development of a population of bottom-fermenting beer yeast by preliminary treatment of seed yeast with light with a wavelength of 980 nm, which can give an economic effect on an industrial scale, is substantiated; the necessity of testing the technological method under study in conditions close to production ones, i.e., for brewing wort with an irradiated suspension of seed yeast, is noted.