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Browsing by Author "Wijerathna, P. A. K. C."

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    Isolation and characterization of native phosphate-solubilizing microorganisms from Eppawala rock phosphate and associated soil
    (Faculty of Science, University of Kelaniya Sri Lanka, 2024) Rathnapriya, R. H. K. G.; Wijerathna, P. A. K. C.; Manage, P. M.
    Phosphorus is a crucial macronutrient in plant growth and development. The lower bioavailability of phosphorus in agricultural lands causes phosphorus deficiency in plants leading to plant growth retardation. As a remedy, rock phosphate is incorporated into phosphorus fertilizers. However, the direct application of rock phosphate as a phosphorus fertilizer is not recommended due to its lower solubility. Hence, the focus of the present study was to isolate and characterize the phosphatesolubilizing microorganisms as a cost-effective greener solution to solubilize insoluble rock phosphate. In the present study, phosphate-solubilizing microorganisms were isolated from rock phosphate and associated soil from the Eppawala rock phosphate deposit in Anuradhapura, Sri Lanka. The Pikovskaya's medium was used for the isolation of microorganisms and their ability to solubilize Eppawla rock phosphate was evaluated using phosphate solubilizing index. The quantification of available phosphate was carried out using the molybdenum blue spectrophotometric method with three replicates and the most efficient isolates were subjected to 16S rRNA and ITS molecular identifications. Statistical analysis was conducted using two-way ANOVA in Minitab, followed by Tukey's pairwise comparison test to identify significant differences between treatments at a 0.05 significance level. Based on the results, fifteen bacterial isolates and one fungal isolate were identified as phosphate-solubilizing microorganisms, with phosphate-solubilizing indexes ranging from 2.12 ± 0.03 to 3.00 ± 0.02. When available phosphorus levels were quantified, four isolates with the highest significant (p < 0.05) available phosphorus concentrations; 36.15 ± 0.64 mg L⁻¹, 33.39 ± 0.53 mg L⁻¹, 29.27 ± 0.65 mg L⁻¹ and 28.87 ± 0.27 mg L⁻¹, were identified. They were identified as Pseudomonas monteilii, Aspergillus niger, Paraburkholderia bannensis, and Burkholderia vietnamiensis respectively. Their phosphate solubilizing indexes were recorded as 2.50 ± 0.05, 2.12 ± 0.03, 3.00 ± 0.02, and 2.33 ± 0.03, respectively. Additionally, a significant reduction (p < 0.05) in the pH in media compared to the control suggests the production of organic acids, a key mechanism used by microorganisms for solubilizing insoluble phosphate. This study confirms the potential of native phosphate-solubilizing microorganisms to solubilize Eppawala rock phosphate, demonstrating its effectiveness as a cost-efficient and environmentally friendly phosphorus source. The results provide key insights into the development of biofertilizers, contributing to sustainable agricultural practices.
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    Quality index assessment for compost derived from municipal solid waste using novel bacterial consortia
    (Faculty of Science, University of Kelaniya Sri Lanka, 2024) Wijerathna, P. A. K. C.; Udayagee, K. P. P.; Idroos, F. S.; Manage, P. M.
    Composting is one of the integral components of the global circular bio-economy platform. Traditional composting requires a prolonged time, and the inoculation of efficient bacterial consortia is a novel technique to enhance the composting rate. Further, assessing compost quality is crucial because the application of immature compost can cause phyto-toxicity, damage the natural ecological balance and disrupt soil structure. The present study focused on the quality assessment of compost produced by five novel microbial consortia (C1–C5) using indexing methods; Clean Index (CI), Fertilizing Index (FI), Germination Index (GI) and Vigor Index (VI). The experiment was conducted using an organic fraction of Municipal Solid Waste (MSW); composed bins made out of concrete were filled with 90 kg of MSW and 2% of v/w each broth consortia were separately inoculated. The experiment was conducted in an open environment, and all the treatments were triplicated. A control treatment with three replicates was used without the addition of any broth consortia. The bins were closely monitored over 30 days for the composting parameters including the pH, conductivity, bulk density and the compost analysis was done following the standard methods. The FI was determined based on the characterization results of the final compost and the CI was determined based on the analyzed heavy metals Cd, Zn, Cr, Pb and Cu analysis carried out using the ICP-OES technique following the acid digestion. The GI and VI were determined using healthy and mature green gram (Vigna radiate) seeds and data were statistically analyzed using Tukey’s test. The FI and CI were calculated using a weighting scale of heavy metals based on their toxicity and the GI and VI were calculated based on the seed germination and their radical lengths. Based on the results, the FI, CI, GI and VI values were significantly different (p < 0.05) and ranged from 3.0–4.5 and 4.0–5.0, 72.4–110.2 % and 364.8–551.0 respectively. Further, the greatest FI, CI, GI and VI values were recorded in the C5 compost, which inoculated the consortium which comprises Bacillus haynesii (PP391133), Bacillus amyloliquefaciens (PP391056) and Bacillus safensis (PP391033) strains. Consequently, the compost produced by the C5 consortium was categorized into the compost quality “A” category indicating its high quality and fertilizing potential. In contrast, the control compost belonged to the compost quality “D” category indicating the lowest quality. Thus, the results evidenced the potential applicability of the C5 consortium to produce good quality compost as a sustainable waste management approach.

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