Department of Biochemistry
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Item Mathematical Modelling of the Growth of Caulobacter crescentus on Caffeine(Hibiscus Publisher, 2018-02-02) Salihu Ibrahim; Abdulrasheed Mansur; Siti Aqlima AhmadCaffeine is a purine alkaloid naturally found in many species of plant and can be degraded by bacteria. Prolong caffeine consumption is well-known to have serious adverse effects. The used of linearization technique using natural logarithm transformation, though standard, is erroneous and can just give an estimated value for the sole parameter measured; the specific growth rate. In this paper, for the first time we present different kinetics models such as Von Bertalanffy, Baranyi-Roberts, modified Schnute, modified Richards, modified Gompertz, modified Logistics and most recent Huang were used to get values for the above constants or parameters from Caulobacter crescentus bacterium growth on caffeine. Huang model was found to be the best model with the highest adjusted R2 value with the lowest RMSE value. The Accuracy and Bias Factors values were close to unity (1.0). The Huang parameters such as Ymax (bacterial growth upper asymptote), λ (lag time), µmax (maximum specific bacterial growth rate) and A or Y0 (bacterial growth lower asymptote) were found to be 1.367 (95% confidence interval of 1.322 - 1.412), 2.683 (95% confidence interval of 2.030 - 3.337), 0.322 (95% confidence interval of 0.252 - 0.392) and 0.324 (95% confidence interval of 0.278 - 0.370).Item Response Surface Methodology Optimization and Kinetics of Diesel Degradation by a Cold-Adapted Antarctic Bacterium, Arthrobacter sp. Strain AQ5-05(MDPI (Multidisciplinary Digital Publishing Institute), 2020-02-02) Abdulrasheed Mansur; Azham Zulkharnain; Nur Nadhirah Zakaria; Ahmad Fareez Ahmad Roslee; Khalilah Abdul Khalil; Suhaimi Napis; Peter Convey; Claudio Gomez-Fuentes; Siti Aqlima AhmadPetroleum hydrocarbons, notably diesel oil, are the main energy source for running amenities in the Antarctic region and are the major cause of pollution in this area. Diesel oil spills are one of the major challenges facing management of the Antarctic environment. Bioremediation using bacteria can be an effective and eco-friendly approach for their remediation. However, since the introduction of non-native organisms, including microorganisms, into the Antarctic or between the distinct biogeographical regions within the continent is not permitted under the Antarctic Treaty, it is crucial to discover native oil-degrading, psychrotolerant microorganisms that can be used in diesel bioremediation. The primary aim of the current study is to optimize the conditions for growth and diesel degradation activity of an Antarctic local bacterium, Arthrobacter sp. strain AQ5-05, using the Plackett-Burman approach and response surface method (RSM) via a central composite design (CCD) approach. Based on this approach, temperature, pH, and salinity were calculated to be optimum at 16.30 ◦C, pH 7.67 and 1.12% (w/v), respectively. A second order polynomial regression model very accurately represented the experimental figures’ interpretation. These optimized environmental conditions increased diesel degradation from 34.5% (at 10 ◦C, pH 7.00 and 1.00% (w/v) salinity) to 56.4%. Further investigation of the kinetics of diesel reduction by strain AQ5-05 revealed that the Teissier model had the lowest RMSE and AICC values. The calculated values for the Teissier constants of maximal growth rate, half-saturation rate constant for the maximal growth, and half inhibition constants (µmax, Ks, and Ki), were 0.999 h−1, 1.971% (v/v) and 1.764% (v/v), respectively. The data obtained therefore confirmed the potential application of this cold-tolerant strain in the bioremediation of diesel-contaminated Antarctic soils at low temperature.Item Effect of Soil pH on Composition and Abundance of Nitrite-oxidising Bacteria(Hibiscus Publisher, 2018-02-02) Abdulrasheed Mansur; Hussein I. Ibrahim; Fatima Umar Maigari; Ahmed F. Umar; Salihu IbrahimNitrification, the microbial oxidation of ammonia to nitrate (NO3-) via nitrite (NO2-) is a vital process in the biogeochemical nitrogen cycle and is performed by two distinct functional groups; ammonia oxidisers [comprised of ammonia oxidising bacteria (AOB) and ammonia oxidising archaea (AOA)] and nitrite oxidising bacteria. Autotrophic nitrification is said to occur in acidic soils, even though most laboratory cultures of isolated ammonia and nitrite oxidising bacteria fail to grow below neutral pH. Published studies revealed that soil pH is a major driver for determining the distribution and abundance of AOB and AOA. To determine whether distinct populations of nitrite oxidising bacteria within the lineages of Nitrospira and Nitrobacter are adapted to a particular range of pH as observed in ammonia oxidising organisms, the community structure of Nitrospira-like and Nitrobacter-like NOB were determined across a pH gradient (4.5 – 7.5) by amplifying nitrite oxidoreductase (nxrA) and 16S rRNA genes followed by denaturing gradient gel electrophoresis (DGGE). The community structure of both Nitrospira and Nitrobacter changed with soil pH, with distinct populations observed in acidic and neutral soils. The abundance of Nitrospira-like 16S rRNA and Nitrobacter-like nxrA gene copies contrasted across the pH gradient. Nitrobacter-like nxrA gene abundance decreased with increasing soil pH, whereas Nitrospira-like 16S rRNA gene abundance increased with increasing pH. Nitrification activity of both Nitrospira-like and Nitrobacter-like NOB in acidic and neutral pH soil was investigated in a microcosm experiment incubated at 30 oC for 21 days, with high rates of nitrification observed in both soils. Findings indicated that abundance and distributions of soil NOB is influence by soil pH.Item Effect of Varying Drying Temperature on the Antibacterial Activity of Moringa oleifera Leaf (Lam)(IOSR Journals (International Organization of Scientific Research Journals), 2015-02-02) Ibrahim I. Hussein; Miriam Mamman; Abdulrasheed MansurThe use of herbal and medicinal plant for traditional therapeutic measure and health care services began since pre-historical time and currently exploited especially in modern medicine. This study investigated the effects of different drying temperature on the antibacterial activity of ethanolic extract of M. oleifera leaf. Fresh leaves of M. oleifera were dried separately at varying temperature by sun drying, oven drying and air drying methods, grinded into powdered form and extracted with ethanol. The ethanolic extracts were used for antibacterial susceptibility test using agar disc diffusion method. All the three clinical bacterial isolates such as E. coli, S. aureus and S. typhiwere susceptible to the ethanolic extract of M. oleifera leaf which signified its antibacterial potency. The air dried extract produced the highest zones of inhibition than the sun dried and oven dried ethanolic extract with 13 mm and 19 mm, 13 mm and 21 mm, 11 mm and 20 mm as the lowest and highest inhibition zones for E. coli, S. aureus and S. typhi respectively. This study inferred that drying temperature especially higher temperature has profound effects on the antibacterial activity of M. oleifera leaf as active component are depreciated