Isolation and identification of phytase-producing Bacillus and Enterobacter species from Nigerian soils

The bioavailability of phosphorus and other nutrients in feed for monogastrics is restricted by the presence of phytate. Exogenous supply of phytase produced by bacteria and other microbes can enhance the bioavailability of these nutrients and reduce phosphorus pollution. The objective of the study was to isolate bacteria with phytase-producing potentials from soil; which may be employed for the bioavailability of phosphorus and other nutrients in feed for monogastrics in Nigeria. Top soil samples were collected from two dumpsites in Lagos, Nigeria and bacteria were isolated and screened for potentials to produce phytase. The isolates with phytase potential were primarily identified by their cultural and biochemical characteristics and then confirmed using the 16S rRNA sequencing, after which their expressed phytases were quantified. A total of six isolates belonging to three species were identified as phytase producers. Sequence data analyses revealed these to be Bacillus subtilis (2), Bacillus amyloliquefaciens (3) and Enterobacter cloacae (1) with accession numbers MH879827 and MH879832; MH879828, MH879830 and MH879831; and MH879829 respectively. Phenotypic phytase activity was highest in E. cloacae ODS 29 (9.69 ± 0.04 U/ml) and least in B. subtilis ODS 10 (8.83 ± 0.02 U/ml). In conclusion, phytase-producing Bacillus and Enterobacter species were isolated and characterized from Nigerian soils. These bacteria species could be used in biotechnological applications. Keywords: Bacillus, Enterobacter, Monogastrics, Phylogenetic analysis, Phytase

GEOTECHNICAL PROPERTIES AND STRENGTH CHARACTERIZATION OF NIGERIAN SOILS

Strength characteristics of foundation soils in the six geo-political zones of Nigeria were evaluated based on standard penetration test (SPT) results using some conventional empirical/analytical models and the bearing capacity was predicted by numerical analysis using Plaxis 3D, a finite element application package. The SPT N-values were first corrected to the standard average energy of 60% (N60) before they were used to correlate soil properties. Evaluation of the soil properties were done at foundation embedment depths of 0.6, 2.1, 3.6, 5.1, 6.6, 8.1, 9.6, 11.1 and 12.6 m. The results of overconsolidation ratio, rigidity index, relative density, angle of internal resistance, undrained shear strength and unconfined compressive strength show that the strength characteristics of Nigerian soils is lowest on the average in the South South (SS) geo-political zone, followed by South West (SW), South East (SE), North East (NE), North West (NW) and the North Central (NC) geo-political zone has the highest prediction of strength characteristics. Bearing capacity generally increased with boring depth and having its lowest values in the SS geo-political zone and increased for the remaining zones in the order of SW, SE, NE, NW and the NC geopolitical zone.

Effect of compost, cow dung and NPK 15-15-15 fertilizer on growth and yield performance of Amaranth (Amaranthus hybridus)

Nigerian soils are generally low in fertility and enhanced crop yield is only possible through external use of organic and inorganic fertilizers. The present study was carried out under field condition at Teaching and Research Farms, Lagos State Polytechnic, Ikorodu to evaluate effects of compost, cow dung and NPK 15-15-15 fertilizer amendments on the growth and yield performances of Amaranthus hybridus. The obtained results indicated that all treatments significantly achieved an increment in morphological parameters (numbers of leaves stem girth, leaf area and plant height) and fresh weight yield comparing with the control. The best results in terms of these characters were obtained in the following order Cow dung > compost > NPK 15-15-15 and control. Post soil analysis shows that all the treatments reduced the soil pH from 6.20 to a range between 5.58-5.68 and available phosphorus, magnesium, organic carbon, total nitrogen and CEC increased significantly compared with control plot. Results suggest that the use of cow dung and composts has potential to improve the growth and yield of amaranth and improves the soil physiochemical properties in the study area.