Cyanide and its complexes are produced by industries all over the world as waste or effluents. Biodegradation is considered to be the cheapest and the most effective method to clean-up cyanide from the environment. Several studies on different types of microorganisms that can degrade cyanide in the environment have been carried out. Hydrolytic, oxidative, reductive and substitutive/transfer reactions are some of the common pathways used by microorganisms in cyanide degradation. Biodegradation of cyanide can occur aerobically or anaerobically depending on the environmental conditions. Immobilized enzymes or microorganisms prove to be very effective method of degradation.

Effect of heavy metals was tested on Serratia marcescens strain AQ07 (accession number: KP213291) to affirm its effect on growth and biodegradation of cyanide. 1 ppm of ten different heavy metals was experimented in-vitro in buffer medium containing 200 ppm potassium cyanide. They are: silver, arsenic, cadmium, cobalt, chromium, cupper, mercury, nickel, lead and zinc. The results obtained illustrates that mercury have significant effect on the growth (optical density 0.13) and biodegradation of cyanide removing only 24.7% compared to the control which has no incorporation of heavy metal (optical density 0.74 and 92% removal respectively) while others remove above 80%. Further studies on mercury reveal that it has significant effect on the bacteria even as low as 0.1 ppm. This illustrates that mercury can significantly hinder biodegradation of cyanide by Serratia marcescens strain AQ07.

This study was carried out to determine the biodegradation potential of bacterial isolates from dye wastewater at Marina Area, Sokoto. Three (3) of the bacteria were identified; Bacillus subtilis, Luteimonasaestuarrii and Bacillus cereus and were used for further studies based on their degradation ability of green, red, yellow and blue dyes. Bacillus subtilis, Luteimonas aestuarii and Bacillus cereus have the potential to degrade all the four dyes used during the present investigation. However, efficacy of the various bacterial strains was found to vary at different concentration levels in degradation of a particular dye. Thus, by this study it can be concluded that Bacillus cereus, Bacillus subtilis and Luteimonas aestuarii can be used as a good microbial source for dye waste water treatment. The selected bacterial species represent a promising tool for application in biodegradation of dye waste water and the potential observed would allow for the application of the bacterial isolates for treatment of dye effluents before disposal. Keywords: effluents, isolates, biodegradation, dye and bacterial.