Degradation of soil cyanide by single and mixed cultures of Pseudomonas stutzeri and Bacillus subtilis

Abstract

Summary The aim of this investigation was to study whether certain bacteria could be used for cyanide degradation in soil. The bacteria Pseudomonas stutzeri and Bacillus subtilis were selected based on their good growth in a minimal medium containing 0.8 mg mL-1 potassium cyanide (KCN). In this study we tested their ability to reduce cyanide levels in a medium containing 1.5 mg mL-1 of KCN. Although both microorganisms reduced cyanide levels, Pseudomonas stutzeri was the more effective test organism. Later on, the selected cultures were grown, diluted and their various cell concentrations were used individually and in combination to test their ability of cyanide degradation in soil samples collected around a cassava processing mill. Bacillus subtilis caused degradation of soil cyanide from 0.218 mg g-1 soil immediately with an inoculum concentration of 0.1 (OD600nm) to 0.072 mg g-1 soil after 10 days with an inoculum concentration of 0.6 (OD600nm) implying a 66.9 % reduction. Pseudomonas stutzeri cell concentration of 0.1 (OD600nm) decreased soil cyanide from 0.218 mg g-1 soil initially to 0.061 mg g-1 soil after 10 days with an inoculum concentration of 0.6 (OD600nm) (72 % reduction). The mixed culture of the two bacteria produced the best degradation of soil cyanide from 0.218 mg g-1 soil sample with a combined inoculum concentration of 0.1 (OD600nm) initially to 0.025 mg g-1 soil with a combined inoculum concentration of 0.6 (OD600nm) after 10 days incubation resulting in an 88.5 % degradation of soil cyanide. The analysed bacteria displayed high cyanide degradation potential and may be useful for efficient decontamination of cyanide contaminated sites.

Microbial Removal of Cyanide Compounds and Soil Cyanide by K. oxytoca

“…In literature, cyanide containing soil samples are generally treated by phytoremediation agents such as Sorghum bicolor, Linum usitassium [34], Eichornia crassipes [35], Salix babylonica [36] and Zea mays [37]. In parallel with our research, in another study it is found that Bacillus subtilis and Pseudomonas stutzeri degraded cyanide in soil (0.218 mg/g cyanide/soil) with the percentages of 66.9% and 72% in 10 days, respectively [38]. In this respect, K. oxytoca culture and sterile crude extract may be used in bioremediation of cyanide in contaminated areas too.…”

Genome-scale reconstruction of the metabolic network in Pseudomonas stutzeri A1501

“…Many metabolic capabilities such as degradation of aromatic compounds [33][34][35][36][37] , denitrification , and nitrogen fixation 38 have been identified in different strains of this species. Various strains of P. stutzeri have been used in biotechnological processes such as biocatalysis production of pyruvate 39 and 2-oxobutyrate 40, 41 , water quality control 42 and degradation of soil cyanide 43 . The entire genome sequence of Pseudomonas stutzeri A1501 has been published in 2008 44 .…”

Biodegradation of Cyanide under Alkaline Conditions by a Strain of Pseudomonas Putida Isolated from Gold Mine Soil and Optimization of Process Variables through Response Surface Methodology (RSM)

“…They demonstrated that cyanide played a role as a substrate until 300 ppm in which the mixture recorded maximum growth rate and cyanide removal. Nwokoro and Dibua [32] examined the degradation of cyanide by single and mixed culture of Pseudomonas stutzeri and Bacillus subtilis, and they reported that P. stutzeri, B. subtilis and their mixture removed cyanide up to72, 66.9 and 88.5%, respectively.…”