Bio-removal of methylene blue from aqueous solution by Galactomyces geotrichum KL20A

The conventional treatments used to remove dyes produced as a result of different industrial activities are not completely effective. At times, some toxic by-products are generated, affecting aquatic ecosystems. In this article, an efficient use of microorganisms is presented as a biodegradation technique that is a safe environmental alternative for the benefit of aquatic life. A strain of the yeast Galactomyces geotrichum KL20A isolated from Kumis (a Colombian natural fermented milk) was used for Methylene Blue (MB) bioremoval. Two parameters of the bioremediation process were studied at three different levels: initial dye concentration and growth temperature. The maximum time of MB exposure to the yeast was 48 h. Finally, a pseudo-first-order model was used to simulate the kinetics of the process. The removal percentages of MB, by action of G. geotrichum KL20A were greater than 70% under the best operating conditions and in addition, the kinetic simulation of the experimental results indicated that the constant rate of the process was 2.2 × 10-2 h-1 with a half time for biotransformation of 31.2 h. The cytotoxicity test based on the hemolytic reaction indicated that by-products obtained after the bioremoval process reached a much lower percentage of hemolysis (22%) compared to the hemolytic activity of the negative control (100%). All of these results suggest that the strain has the capacity to remove significant amounts of MB from wastewater effluents.