Phosphorus Removal Capability of Aspergillus Terreus and Bacillus Subtilis from Nigeria’s Agbaja Iron Ore

Abstract

Comparative phosphorus removal capability of a microbial fungus-Aspergillus terreus and a bacterium-Bacillus subtilis from Nigeria’s Agbaja iron ore was investigated. Manual crushing and sieving of the iron ore in Shital Test Kits produced 5 grain size distributions namely: ≥1.0mm, 1.0mm/0.50mm, 0.50mm/0.25mm, 0.25mm/0.125mm, 0.125mm/0.00mm, from which the first and last grain sizes were excluded from the experiment on technical grounds. Then 1g of each of the remaining 3 grain sizes was carefully weighed for each set of experiment. Culturing and subsequent inoculation of the microbes (which are native to the iron ore) in conical flasks containing sterilized, weighed iron ore samples in 100ml of equally sterilized malt extract and nutrient broths were left to stand for 7 weeks in the laboratory. At weekly interval, the samples were removed, treated through series of chemical reactions to obtain ammonium phosphomolybdate precipitate which was back-titrated with 0.1 N-HCl to determine the amount of phosphorus left in samples and consequently, the amount removed. The research found out Aspergillus terreus and Bacillus subtilis have separately and successfully removed phosphorusa deleterious non-metalic inclusion from Nigeria’s Agbaja iron ore, which previously defiled all attempts at phosphorous removal and beneficiation techniques. However their ability at phosphorus removal was promising and varied with the grain sizes of ore. Across all grain sizes used, 58% and 66% phosphorus was removed in 7 weeks, respectively by the two microbes. It was also obvious that the capacity of the microbes in removing phosphorus was seriously hampered by a decline in activity as indicated by the reduction in microbial population in the microcosm. For B. subtilis the density of viable cells increased from an initial load 3.4 x 10 5 cfu/ml, at the beginning of experiment, to 2.2 x 10 7 in 2 weeks but later declined to 0.9 x 10 6 cfu/ml at the end of 7 weeks. For A. terreus the initial biomass weight of 1g inoculated increased to 1.993 g dry weight within 3 weeks but later decreased to 0.910g dry weight in the 7 th week. The reduction in microbial activity may be attributed to antimicrobial components of the ore, pyrite, and other heavy metals which may have affected the phosphorus uptake from ore. Our findings have confirmed the stronger phosphorus removal capability of B. subtilis under submerged culture technique. It is however suggestive that A. terreus may perform optimally if the submerged medium is constantly aerated.