ABSTRACT
Aims: To effectively exploit the atrazine degrading capabilities of Nocardioides spp. isolated from agricultural soil samples in Nigeria and ascertain the effect of pH, temperature and nutrient addition on the degradation process. Methodology and results: Isolates were cultivated on atrazine mineral salts medium at a temperature range of 4 °C - 45 °C and a pH range of 3-10. An optimum atrazine degrading activity was observed in the isolates between temperatures of 25 °C and 37 °C and between pH 5 and 8. Different carbon sources (glycerine, glucose, chitin, cellulose and sodium citrate) and nitrogen sources (urea, biuret, cyanuric acid, potassium nitrate and ammonium chloride) were also added to the medium. The addition of carbon and nitrogen sources did not increase degradation rates although urea and glycerine repressed the degradation ability of the isolates. Statistical analyses of variance at P < 0.05 showed no significant differences in the growth and degradation rates by both bacterial isolates under these conditions. Conclusion, significance and impact study: Atrazine degradation by Nocardioides spp. is pH and temperature dependent, and requires no additional sources of carbon and nitrogen. Hence, its use in bioremediation of atrazine contaminated agricultural soil should be explored.
Subject(s)
AtrazineABSTRACT
Aims: The presence of lignocelluloses, especially sawdust in the Lagos lagoon and the attendant ecological problems warranted studies on their degradation. This study aimed to isolate and identify the indigenous bacterial strains capable of utilizing lignocellulosic wastes under the prevalent tropical estuarine conditions. Methodology and results: Nine bacterial species were obtained by elective culture from decomposing wood residues in the lagoon. They were identified on the basis of morphology, biochemical characteristics and analysis of their 16S rRNA gene sequences as Streptomyces, Bacillus and Paenibacillus species. They were cultured on various ligninrelated lignocellulosic substrates over a period of 7 to 12 days. All the isolates showed moderate to very good growth on sugarcane baggase. Streptomyces albogriseolus strain AOB and Paenibacillus sp. ROB showed good growth on grass while on sawdust, only Streptomyces AOB, and Bacillus megaterium strain NOB showed good growth. High performance liquid chromatographic analysis showed that the Streptomyces species completely utilized coniferyl alcohol, B. megaterium strain NOB utilized 90-100% of all the lignin- related aromatic compounds. All the bacterial species utilized less than 40% of sinapyl alcohol, Bacillus sp. OOB and Paenibacillus sp. strain ROB failed to utilize vanillic acid. Conclusion, significance and impact of study: The isolates degraded lignocellulosic wastes and lignin-related compounds. The role of fungi in the breakdown of lignocellulose in the Lagos lagoon had been the subject of previous research considerations whilst the role of bacteria spp was unreported. Autochthonous bacterial species may equally play a role in the bio-rehabilitation of the sawdust-polluted water of the Lagos lagoon. Keywords: Lignocellulose, Streptomyces, Bacillus, Paenibacillus, pollution