Science
Permanent URI for this communityhttp://repository.kln.ac.lk/handle/123456789/1
Browse
4 results
Search Results
Item Degradation of selected pesticides in soil in selected areas in Medawachchiya and HPLC analysis of pesticides(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Dassanayake, D. S.; De Silva, R. C. L.It is known that diabetes, hypertension and different forms of glomerular nephritis are known etiologies of Chronic Kidney Disease (CKD). However, over the last two decades, a new strain of CKD known as Chronic Kidney Disease of unknown etiology (CKDu) has been endemic around the rural agricultural communities of the North Central Province of Sri Lanka. It is not related to a known cause commonly identified with CKD. Agrochemicals used is believed to be a cause of CKDu. Analysis of pesticide is often difficult due to interference and decomposition. Previous studies have noted that there were suspected peaks for ‘Diazinon’ and ‘Profenofos’ pesticides in the HPLC chromatograms of soil samples collected from Medawachchiya. Therefore, in order to test the presence of those pesticides in the ground, soil samples were collected and analyzed from selected cultivated areas of Medawachchiya were spiked with both Diazinon and Profenofos pesticides. Thirty representative soil samples (five samples per paddy field) were collected from six paddy fields from Karanbankulama Grama Niladhari division in Medawachchiya. Each soil sample was spiked with Profenofos (5.00 mg L-1) and Diazinon (5.00 mg L-1). Samples were digested using soxhlet extraction, from which the pesticide residues were extracted using solvent extraction. The extracts were analyzed through High Performance Liquid Chromatography (HPLC) analysis. Retention time of Diazinon at 5.89 minutes and that of Profenofos at 6.74 minutes and both peaks were detected throughout the study. When overlaid, the HPLC chromatograms of the non-spiked and spiked soil samples the same background peaks in non-spiked soil chromatogram were present in spiked soil chromatograms as well which resulted due to the common soil components retained in this soil. The results suggest presence of pesticide residue in the sample. The spiked pesticides are retained in soil samples throughout the study and the amount is decreased due to the degradationItem Screening of microcystin and microcystin-producing genes in Labugama and Kalatuwawa reservoirs in Sri Lanka(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) De Silva, I. U.; Manage, P. M.Microcystins (MCs) are the most widely studied carcinogenic cyanobacterial hepato- and neurotoxins. The MCs are synthesized by a non-ribosomal pathway through a multifunctional enzyme complex known as microcystin synthetase (mcy) encoded by the mcy gene clusters. The present study was aimed to screen MCs and MC-producing genes in Labugama and Kalatuwawa reservoirs which satisfies 60% of drinking water requirement for Colombo District. In the study, plankton and water samples were collected from the two reservoirs prior to water treatment process. The sampling was performed using a boat on the first week of each month from August to October in 2017 where three sampling locations were selected to collect water at each sampling time. Horizontal plankton samples were collected at 10 cm depth in each location using a 55 µm plankton net while the boat was moving. Water temperature and pH were measured on site using digital meters. Total inorganic nitrogen (N-NO3-, N-NO2-, N-NH3) and total phosphorous were determined using standard spectrophotometric methods, and cyanobacteria were identified under a light microscope using standard algae and cyanobacteria identification keys. Microcystis spp. were isolated and monocultures were prepared on cyanospecific BG 11 media from which the genomic DNA was extracted for the screening of MC-producing gene cluster in water samples using the Polymerase Chain Reaction (PCR). MCs were analysed by High Performance Liquid Chromatography (HPLC) and Enzyme Linked Immunosorbent Assay (ELISA) respectively. Temperature of water samples ranged between 27.8 and 28 oC while pH fluctuated in a range between 7.2 and 7.5. Total inorganic nitrogen was recorded from 0.02 to 0.03 mg/L and total phosphorous fluctuated from 0.01 to 0.02 mg/L during the sampling period. Microcystis spp. was identified as dominant cyanobacteria in cell density range between 176 and 226 cells/mL for both reservoirs. Amazingly, MCs were not present at detectable levels following the HPLC method (detection limit 0.5 mg/L) and ELISA method (detection limit 0.1 µg/L). Also, the PCR amplification showed the absence of mcy cluster genes E, A and B in the water samples. Thus, the results of the study revealed that both Labugama and Kalatuwawa reservoirs have non toxic strains of cyanobacterium Microcystis spp. The results of the present study were supported HPLC, ELISA analysis and molecular analysis.Item Usage of Strychnos potatorum seeds for the reduction of diazinon residues in water(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Nawarathne, W. N. C. P.; Mathota-Arachchige, Y. L. N.The need to fulfil the current food demand has led to the heavy usage of agrochemicals such as synthetic fertilizers, pesticides, and herbicides in agricultural sector. However, pesticide malpractices can cause severe adverse effects on both human health and the environment. Therefore, removal of remaining pesticide traces from water prior to human consumption is essential. Among the organochloride pesticides used in Sri Lanka, diazinon was selected as the candidate pesticide for this model study considering its common usage in local agriculture. Strychnos potatorum (SP) is a plant which can be found in central parts of Asia. In several studies, SP seeds have been effectively used for treating polluted water. Therefore, SP seeds were used as the material to treat Diazinon contaminated water. The objective of this study was to assess the efficiency of reduction of diazinon residues from water using raw SP seeds. High Performance Liquid Chromatography (HPLC) analysis was used to determine the diazinon concentration in the medium and the peak for diazinon was identified at ~12 min detected at 254 nm using Agilent infinity 1260 II HPLC performed in a reversedphase Zorbax Eclipse plus C18 Column, with a mobile phase consisting of acetonitrile/water (65/35, v/v) at ambient temperature with an injection volume of 10 µL and flow-rate at 1 mL/min. Optimization of SP biomass dose/seed biomass was performed by agitating diazinon aqueous solution (10 mg/L, 50.0 mL) with different SP seed pieces varying from 10 g to 50 g. Biomass optimization was done for different agitation conditions (1-inch-long and 1.5-inch-long magnetic bar sizes). Two different biomass-diazinon interaction quenching techniques (filtering using filter paper and centrifugation) were tested. Optimization of treatment time was performed by agitating diazinon aqueous solution (10 mg/L) and SP seed pieces (0.2 g/mL). Treatment was conducted up to 120 mins. A control study was carried out by providing conditions similar to the treatment study without using SP biomass/ seed biomass. Results of this study revealed that SP seed is an effective material for reduction of the diazinon pesticide from the water which showed 67 ± 10% diazinon concentration reduction. The efficient SP biomass was identified as 0.2 g/L for 10 mg/L diazinon concentration. The reduction of diazinon concentration was higher with the use of 1.5-inch magnetic bar than the 0.5-inch magnetic bar which revealed that stirring mechanism was significant for the diazinon reduction. The optimum time of treatment was identified as 100 min for SP seeds 0.2 g/mL and for the 10 mg/L solution of diazinon.Item Isolation, purification and structure elucidation of antimicrobial and bio-active compounds of soil fungi.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Wijesekara, W. A. M. A.; Wijesinghe, K.D.; Kumara, K. G. N. P.; Manage, P. M.Soil fungi are considered as a rich source of bioactive compounds and antibiotics. They are able to produce a great variety of secondary metabolites characterized by a broad spectrum of properties of bioactive compounds including antiviral, antibacterial, antifungal, and anticancer. Therefore, the objective of the study was isolation, purification and structure elucidation of antimicrobial and bioactive compounds of soil fungi. In the present study, soil samples were collected from the Kelani River mouth, Sri Lanka and twenty nine fungi were isolated on potato dextrose agar. The antimicrobial activity of the methanol crude extract of fungi was tested against two human pathogenic Gram-positive bacteria (Bacillus sp., Staphylococcus aureus-ATCC 2593), two human pathogenic Gram-negative bacteria (Escherichia coli-ATCC 25922, 2785 and Salmonella typhi) and two human pathogenic fungi (Candida albicans and Candida tropicalis) using agar disc diffusion method. One fungal isolate was selected based on the diameter of inhibition zone to isolate and purify antimicrobial (antifungal and antibacterial) compound. The antioxidant property in the crude extract was evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging test (Inhibitory Concentration, IC50 = 200.42 ppm). Secondary phytochemical screening for major classes of antibacterial compounds were done using TLC visualization reagent specific for major classes of antibacterial compounds. Structural elucidation of isolated compound was carried out using Gas Chromatography Mass Spectrometry (GC-MS) and Fourier-Transform InfraRed spectroscopy (FTIR). TLC plates of the crude extract developed using different solvent system showed different number of band with antimicrobial compounds as it is revealed by bioautochromatography, solvent system 1 ( Ethyl Acetate (EA): Methanol (Me): Water (Wa) (100:13.5:10) 6 bands against Bacillus sp. solvent system 2 ( EA :Toluene (93:7) ) 2 bands against Bacillus sp. and two bands with antifungal activity was recorded against C. albicans. Band with antimicrobial compounds on Preparative Thin Layer Chromatography (PTLC) was scraped and dissolved in methanol (HPLC) to further purify using Solid Phase Extraction (SPE) and High Performance Liquid Chromatography (HPLC). Antibacterial activity of each purified compounds, was verified using bioautochromatography. According to the secondary chemical screening, the compound with the highest antimicrobial activity was found to have contain Arbutin and Anthraquinone glycoside. The results of the present study revealed that the crude extracts of soil fungi had antibacterial activity against some human pathogenic bacteria and the soil fungi is a potential candidate to utilize as a source to produce antibiotics.