Browsing by Author "Handagiripathira, H.M.N.L."

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Arginine Decarboxylase from the pathogenic fungi, Colleotrichum gleosporosides : Purification and Properties
(Journal of Science of the University of Kelaniya Sri Lanka, 2003) Weerasooriya, M.K.B.; Handagiripathira, H.M.N.L.; Wijewickrama, G.T.
Arginine decarboxylase, a polyamine biosynthetic enzyme, was isolated from a phytopathogenic fungi, Colletotrichum gleosporoides, which causes Anthracnose in wide range of plants in many parts ofthe world. The enzyme was purified 25 fold with 16.7% recovery by elution through Sepharose 4B gel column and DEAE Cellulose ion exchange column. As determined by Sepharose 4B gel chromatography, the native molecular mass of the purified enzyme was ~265kDa. SDS-PAGE of the purified enzyme showed two bands around 65 kDa and ~25 kDa, suggesting that possibly this enzyme could be a hexamer of above two sub units. Optimum pH and temperature for the enzyme was 5.2 and 40�C respectively . Beyond 50�C enzyme activity slowly declined and was almost deactivated by 80�C. Approximate Km of the enzyme for the substrate arginine was 67mM.
Assessment of the Heavy Metal Concentrations in Mangrove Leaves of Negombo Lagoon
(19th Conference on Postgraduate Research, International Postgraduate Research Conference 2018, Faculty of Graduate Studies,University of Kelaniya, Sri Lanka, 2018) Handagiripathira, H.M.N.L.; Deeyamulla, M.P.; Koichiro, S.
Mangrove ecosystems play an important role in the biogeochemistry of heavy metal contamination in tropical coastal areas. During the last decades, heavy metals are one of the most serious contaminants in those environments due to its toxicity, durability and bioaccumulation problems with the long residence time within the food chain. Mangrove leaves are the primary producer of the food chains or food webs in mangrove ecosystems where there is a direct effect on the human health. The bioaccumulation levels of heavy metals in mangroves can be estimated by assessing such levels in leaves, sediments and water in the study area. This study was a part of a M.Phil. research and the main objective of this study was to assess the concentrations of selected heavy metals to understand the levels of contamination in the mangrove leaves in a selected lagoon system. The 27 locations of Negombo lagoon which is situated in urbanized area in Gampaha District of Sri Lanka was selected for the study. Four mangrove species of Rhizophor amucronata, Rhizophora apiculata, Avicennia marina and Lumnitzera racemosa were chosen since these arethe most common species in the lagoon. Mangrove leave samples categorized as young, matured and old and were collected in the wet and dry seasons of 2015 and 2016. Leave samples were cleaned and oven dried prior to grinding for fine powder. The elemental concentrations of heavy metals, Mn, Fe, Cr, Co, Ni, Cu, Zn, As, Hg and Pb were analyzed in the dried powder of mangrove leaves (297 samples) using Particle-induced X-ray emission (PIXE) technique established in Medical University, Iwate, Japan. The results were evaluated to study the spatial and temporal variations of heavy metal concentrations in mangrove leaves of the Negombo lagoon. The distribution of metals in mangrove leaves were departed and depended on the mangrove species as well as climatic seasons in study period. The most prominent species of R. mucronata, R. apiculata were represented by 262 samples and both species were having same concentration levels except Mn and Zn, which act as essential plant nutrients, were greater in R. apiculatathan the other species. The ranges of metal concentrations (in ppm) of R. apiculata leaves in the studied area were observed in the order: Mn (15.2-453.0) > Zn (5.4-276.4)> Fe (28.6-224.9) > Cu (0.1-9.3)> Cr (0.2-7.3)> Hg (ND-5.9)> Pb (ND-4.0)> Ni (ND-2.3)> Co (ND-1.7)> As (ND-1.0). The heavy metal uptake by young, matured and old leaves were showed significant deviations for most of the studied metals. Cr content in all leaves was same and some metals (ie. Fe) were higher in old leaves and some metals (ie. Zn) were higher in young leaves. A comparative evaluation of studied metals was carried out with the similar studies conducted in the world. In general, heavy metal concentrations in mangrove leaves of Negombo lagoon were lower than the permissible limits as recommended by WHO (1996), except Cr, Zn and Pb
Stable isotopic characterization and baseline monitoring on mangrove ecosystem in Negombo lagoon using carbon and nitrogen stable isotopes
(Faculty of Graduate Studies, University of Kelaniya, 2015) Handagiripathira, H.M.N.L.; Deeyamulla, M.P.; Rogers, K.; Waduge, V.A.
The stable isotope ratios of 13C/12C and 15N/14N and the weight ratio of total carbon to total nitrogen (C:N) are important indicators in the field of environmental monitoring. As a part of the assessment of nutrient enrichment in Negombo lagoon ecosystem, stable isotope technique is used to study the stable isotope ratios of mangroves and adjacent water. Although this technique is an advanced tool to identify the fingerprints of environmental pollutant sources, totally newel to the research field in Sri Lanka. The fresh mangrove leaves (young, matured and old) of Rhizophora apiculata and Rhizophora mucronata spices, totally 35 samples and 10 surface water samples were collected from 12 sampling points randomly selected from the bank of Negombo lagoon. The leaves were rinsed with distilled water, oven dried at 40 0C for 48 hours and powdered. The water samples were filtered into glass fiber filters to collect suspended particulate materials in the water and filter papers were oven dried at 40 0C for 24 hours. Samples were analyzed by combustion on a Eurovector elemental analyzer coupled to an Isoprime mass spectrometer in GNS science, New Zealand. There were some effects of %Nitrogen (%N) on the old leaves where the %N is quite low (range 0.3% to 1.7% with a mean value of 0.6%), but generally young and matured leaves had similar trend in % N (range 1.1% to 2.9% with a mean value of 1.8% and range 0.7% to 2.9% with a mean value of 1.5% respectively). The behavior of isotopic Nitrogen-15 ratio (15N) in those three types of mangrove leaves was significantly divers compared with behavior of %N in leaves. The range of 15N in young and matured leaves was from 2.3‰ to 12.3‰ with a mean value of 5.4‰ and this ratio in old leaves had a range from 5.1‰ to 8.0‰ with higher average of 6.52‰. The average % Carbon values (%C) of all the three types of mangrove leaves were in the range of 42% to 43%. The isotopic Carbon-13 ratio (13C) of young, matured and old leaves was within the common range for C3 plants, with values ranging from -25.4 to -32.7‰ and average of -29.5‰. The total Carbon to total Nitrogen ration (C: N, atom) had increased in older leaves (range 36.2 to 163.3 with mean value of 120.8), and significantly decreased in matured and young leaves (average values of 41.9 and 34.5 respectively). The average 13C value of the lagoon water was -24.6‰ and average 15N value of the water was 6.7‰. The carbon and nitrogen isotopic compositions obtained in this study are comparable with previously published results in the other coastal regions of the world. As an initiative research study on the stable isotope analysis in Sri Lanka, the results and findings, generated in this study can be considered as the baseline data for future studies based on the lagoon ecosystem.