ABSTRACT
Aim: To assess natural electrogenicity and bioelectricity generation potentials of microbial isolates from water sites in Nigeria Study Design: Sampling of various water sites and microbial isolation for subsequent electrogenic characterization of isolates and bioelectricity generation Place and Duration of Study: Department of Microbiology, University of Ibadan, Ibadan, Oyo state, Nigeria between January 2014 to June 2015. Methodology: Various water sites in Nigeria were assessed, and samples collected. Isolation and identification of bacteria and yeasts were carried out using standard techniques. Electrogenic screening of pure culture using Open Circuit Voltage (OCV) measurements in biolelectrochemical reactors and Cyclic Voltammetry were carried out. Bioelectricity generation measurements using multimeters and calculations of Voltage, Current, Power and Coulombic efficiency in Open and Closed circuit systems were calculated. Results: A total of 362 microorganisms (254 bacteria; 108 yeasts) were isolated and screened for electrogenicity. Samples from a River Benue site in Yola, Nigeria harboured the highest number of electrogenic isolates among all sites assessed. Sixty-five microorganisms elicited electrogenicity out of which 47 were bacteria and 18 were yeasts. Based on their electrogenic potentials, 7 of the most efficient isolates with electrogenic voltages >500 mV were further selected, and molecularly identified by 16S rRNA and ITS region gene analyses as Pseudomonas aeruginosa A4 (KX397030), Pseudomonas aeruginosa B3 (KX397029), Enterobacter aerogenes 102 (KX397032), Pseudomonas sp. B1 (KX397031), Pseudomonas aeruginosa 104, Bacillus cereus 101 (KX397028) and Pichia kudriavzevii 103 (KX397033). Cyclic voltammetry carried out on the isolates confirmed their electroactivity in comparison with a non-electrogenic Escherichia coli ATCC 25922 strain. Bioelectricity generation experiments showed that P. aeruginosa A4 was the most electrogenic strain, eliciting the highest current of 86.37 ± 14.52 mA/m2. The least current was observed for the Pichia kudriavzevii 103 strain (19.22 ± 9.02 mA/m2). Conclusion: All isolates proved to be good electrogens and efficient candidates for optimising bioelectricity production.
ABSTRACT
Aims: This study was aimed at screening fungal isolates from degrading wood samples for β 1,4-xylosidase production, selecting the best isolate based on the screening test to produce the enzyme through solid state fermentation of some wood shavings and determining optimum production conditions for the fungus on best substrate. Place and Duration of Study: Microbial physiology laboratory, Department of Microbiology, University of Ibadan, Ibadan and Multi Discplinary Central laboratory University of Ibadan, Oyo State Nigeria. Between September 2010 and October 2011. Methodology: Isolates obtained from degrading wood samples were identified and screened on agar plates of para–nitrophenyl β-xyloside as carbon source. Selected isolates were used to produce β 1,4-xylosidase using shavings of Anogeissus leiocarpus, Gmelina arborea and Terminalia superba moistened with a chemically defined medium as substrates. Assay was done every 3 days for 15 days. Production dependent parameters such as pH, temperature were varied on the best wood substrate for β 1,4-xylosidase production by selected fungus. Results: Selected isolate was used for enzyme production on shavings of Anogeissus leiocarpus, Gmelina arborea and Terminalia superba as substrates, each was moistened with chemically defined medium. Assay was done every 3 days for 15 days. Production dependent parameters such as pH, temperature were varied on the best wood substrate for β 1,4-xylosidase production by fungus. Maximum β 1,4-xylosidase activity of fungus on each substrate was; Anogeissus leiocarpus, 31.620Ug-1 on 12th day, G. arborea, 8.935U g-1 on day 9 and T. superba, 6.053Ug-1 on 6th day. Optimum β 1,4-xylosidase production was obtained on A. leiocarpus at 35ºC and pH 6 with 40% and 60% aeration. 50% moisture content of substrate supplemented with soy meal as nitrogen source supported the best β 1,4-xylosidase production by fungus. Conclusion: Enzyme production was highly enhanced at optimum conditions.