ABSTRACT
Environmental contamination with dichlorodiphenyltrichloroethane (DDT) has sever effects on the ecosystem worldwide. DDT is a recalcitrant synthetic chemical with high toxicity and lipophilicity. It is also bioaccumulated in the food chain and causes genotoxic, estrogenic, carcinogenic, and mutagenic effects on aquatic organisms and humans. Microbial remediation mechanism and its enzymes are very important for removing DDT from environment. DDT and its main residues dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD) can biodegrade slowly in soil and water. To enhance this process, a number of strategies are proposed, such as bio-attenuation, biostimulation, bioaugmentation and the manipulation of environmental conditions to enhance the activity of microbial enzymes. The addition of organic matter and flooding of the soil enhance DDT degradation. Microbial candidates for DDT remediation include micro-algae, fungi and bacteria. This review provide brief information and recommendation on microbial DDT remediation and its mechanisms.
ABSTRACT
Hexavalent chromium is resistant to degradation and harmful toxic substance to environment and community health. Physicochemical 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 fungi from farm soil & industry effluent for mycoremedation purpose. The screening and isolation of yeast was carried out on potato dextrose agar media. PDA and broth assay test for fungi tolerance to hexavalent chromium at different concentration, temperature and pH was evaluated. Fungi species was identified biochemically using Biolog Microstation depending on carbon utilization and chemical sensitivity test. The result revealed that 10 yeast species was identified with full ID from effluent waste and farm soil based on their probability ≥ 75% and similarity index ≥ 0.5 as well as their Cr (VI) tolerance ability up to 2500 ppm. 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), Schizoblastosporonstarkeyihenricii (89%, 0.56), Endomycopsis vivi (84%, 0.62), Rhodotorula pustula (Sim, 0.59). Two yeast species Yarrowia lipolytica and Nadsoniafulvenscens show the highest growth mean Optical density (OD) measure 0.74 ± 0.2 & 0.60 ± 0.2 respectively at pH 7 & 25 °C. The highest tolerance index (mm) was recorded by Schizoblastosporon starkey henricii 0.3067 ± 0.152. Cr (VI)-tolerance ability of these yeast strains used in the development of chromium-bioremediation technologies provide an alternative option for chromium sequestration after HPLC analysis& molecular characterization.
