Hexavalent chromium tolerant fungal species identified from urban vegetable farm and effluent waste in Addis Ababa & Rift valley, Ethiopia

Abstract

Abstract Hexavalent chromium is resistant to degradation and sever toxic substance to environment and community health. Physico chemical treatment methods are demanding high cost, used large quantities of chemicals & energy, release large amount of secondary toxic degradants. Mycoremediation is an eco-friendly alternative treatment method. The main objective of this research is to isolate and characterize chrome (VI) tolerant yeast from farm soil & industry effluent for mycoremedation role. The screening and isolation of yeast was carried out on potato dextrose agar media. Solid agar and broth assay test for yeast tolerance on hexavalent chromium at different concentration, temperature and pH was evaluated. Yeast species was identified biochemically using Biolog Microstation depending on carbon utilization and chemical sensitivity test. The result revealed that 11 yeast species was identified from effluent waste and farm soil based on their probability >75% and similarity index >0.5 as well as their hexavalent chromium tolerance ability up to 2500ppm. These are Yarrowia lipolytica (100%,0.7) Cryptococcus luteolus(100%,0.64), Rhodotorula aurantiaca A (100%,0.62), Ustilago maydis (100%,0.58) Trichosporon beigelii B (100%,0.51),Cryptococcus terreus A (100%,0.62), Zygosaccharomyces bailii (98%,0.65), Nadsoniafulvenscens (90%,0.62), Schizoblastosporon starkeyi henricii (89%,0.56), Endomycopsis vivi (84%,0.62), Rhodotorula pustula (Sim 0.59). Two yeast species Yarrowia lipolytica and Nadsonia fulvenscens show the highest mean Optical density (OD) measure (0.953+0.43), (0.96+0.400) respectively at pH4 &25OC. Cr (VI)-tolerance ability of these yeast strains used after further HPLC analysis& molecular characterization in the development of chromium-bioremediation technologies provide an alternative method for chromium sequestration.