Browsing by Author "Seneviratne, G."

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    Cellulase Activity of Fungal and Bacterial Isolates and their Fungal-bacterial Biofilms
    (Uva Wellassa University of Sri Lanka, 2021) Singhalage, I.D.; Palliyaguruge, A.P.; Kannangara, U.D.; Seneviratne, G.; Madawala, H.M.S.P.; Yogarajah, K.
    Enzymes are crucial in speeding up many biological reactions, but the lack of suitable sources to extract them with high productivity in low cost is a constraint. Present study designed in order to evaluate the cellulase production by some fungal and bacterial isolates and their fungal-bacterial biofilms (FBBs). Five fungal (F1-F5) and 27 bacterial (B1-B27) strains were isolated from soil samples collected from a municipal garbage dump near Vincent Dias Stadium, Badulla, Sri Lanka. All bacterial isolates were screened for cellulase activity using Congo Red Agar medium. Two strains (B6 and B15) with significant (p ≤ 0.05) cellulase activity were selected along with all fungal strains for biofilm formation. Accordingly, ten fungal-bacterial combinations (F1B6, F1B15, F2B6, F2B15, F3B6, F3B15, F4B6, F4B15, F5B6, F5B15) were used for the formation of biofilms under in vitro conditions. The biofilm formation was monitored regularly through microscopic means. On day four, three successful biofilms (B6F1, B15F1 and B15F4) were resulted with bacterial cell attachment to mycelia. These three mixed-culture biofilms and their monoculture counterparts were re-cultured in Czapek-Dox broth with the culture medium alone as a control. On day four , a portion of the broth was centrifuged and the supernatant was used as the crude cellulase extract. The extracts were then tested for their efficacy through a well diffusion assay using Carboxymethyl Cellulose agar medium in a Complete Randomized Design with three replicates. The diameters of the clear zones around the wells were measured and the data were analyzed by one-way ANOVA and t-test. The B15F1 showed a significantly higher cellulase activity over F1, the second highest cellulose producer (p = 0.02). F3 and F4 also showed considerably high levels of cellulase activity. The least cellulase activities were shown by B6 and B15. Thus, the fungal-bacterial biofilm B15F1 can be introduced as a potential source for bulk extraction of cellulases. However, further studies are needed to find out the optimal maturation stage with the highest cellulase activity of the biofilm, B15F1. Keywords: Cellulase; Bacteria; Fungi; Fungal-bacterial biofilms
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    Degradation of Cellulose and Pectin in Organic Wastes by Developed Fungal-Bacterial Biofilms
    (Uva Wellassa University of Sri Lanka, 2018) Wickramage, K.C.; Singhalage, I.D.; Seneviratne, G.
    An organic waste consists of cellulose and pectin which are resistant to rapid degradation due to their complexity. The objective of this study was to find out the most efficient fungal-bacterial biofilm/s (FBB/s) for the organic waste degradation. Pectinolytic and cellulolytic activity of isolates were tested by standard plate assays and best strains were used to develop 25 FBBs. The best FBBs were selected based on the physical attachment of bacterial cells to fungal filaments (light microscopic observations), and those were symbolized as F3B1, F5B1, F2B2, F3B2, F3B3, F4B3, F2B5 and F3B5. Coffee silver skin, barely skin and rice husk were the organic wastes used. Developed FBBs were inoculated separately to 10 g of above wastes in petri dishes and were incubated for 40 days. The control was maintained without FBBs inoculation. Three replicates were maintained for each treatment and the experiment was arranged in a completely randomized design. The mass reduction, Fourier Transform Infrared Spectroscopy (FTIR) and sugar accumulation of samples were analyzed within five day intervals. Data were analyzed by ANOVA. Results revealed that in the 40th day, the sugar production was highest in barley husk treated by F3B5. In coffee silver skin, the sugar accumulation was similar under all FBBs. In rice husk, F3B1 showed the highest sugar level in 15th day, but F4B3 dominated on the 25th day. The mean weights of the samples decreased with time, but after 25th day they came into a plateau with having 0.1-0.3 % weight loss percentage. According to FTIR data, all FBBs except F3B3 showed the degradation of barely husk. F2B5 was the best in terms of weight loss during the last five days of incubation. F4B3, F3B2 and F5B3 were the best biofilms in terms of weight loss at the end of 10th, 15th and 20th days, respectively. It can be concluded that F3B3 and F3B2 were the best FBBs for degradation of all three types of organic wastes. Keywords
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    Development of Biofilmed Biofertilizers for Bean (Phaseolus vulgaris)
    (Uva Wellassa University of Sri Lanka, 2010) Peries, C.M.; Seneviratne, G.
    Soil nitrogen deficiency may result in poor yields or failed crops and has traditionally been overcome by applying chemical fertilizers. But it is more expensive and can be harmful to the environment. The associations between fungi and root nodulating rhizobia as Fungal-Rhizobial Biofilms (FRBs) in leguminous plants is advantageous due to their ability to convert atmospheric nitrogen in to useful form in a process known as Biological Nitrogen Fixation (BNF). Although common bean (Phaseolus vulgaris) is the most frequently consumed legume worldwide, the yield is low and the plants have a low nitrogen fixing capacity compared to other legume plants. Therefore, this study describes the potential application of developed FRBs as Biofilmed Biofertilizers (BBs) to improve bean crop production. Biofilms were developed by combining bacteria and fungi isolated from the bean root nodules and rhizosphere. Then the developed biofilms were applied to the bean plants, which were grown in pots inside a greenhouse. These were compared with chemically fertilized plants. After 25 days from germination (early growth), dry weight of shoot, root and nodules of the plants were measured. Means of shoot, root and total plant dry weights of the treatments were compared using student's T-test. Three different types of fungi and bacteria were isolated from the bean root rhizosphere, according to their morphological differences. A successful biofilm formation was observed between selected fungi and bacteria isolated from the root rhizosphere. Among the treatments applied with BBs, those with Rhizobium showed better performance such as higher shoot and root dry weight with low variability and higher nodule dry weight during early growth stage. The results obtained by applying developed BBs to bean showed relatively low initial shoot growth compared with the chemical fertilizer applied bean plants due to competition between microbes of the BBs and the plant for nutrient acquisition. At harvest, the nodulation had just started. Plant biomass did not reflect the contribution of nodulation and biological nitrogen fixation, due to harvest in early growth. Therefore, further studies are necessary to evaluate the effect of BBs on bean at maturity. Key words: Biofilms, Biofilmed biofertilizers, Common bean
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    Development of Microbial Biofertilizer for Tomato (Solanum Lycopersicum)
    (Uva Wellassa University of Sri Lanka, 2019) Maheshika, W.A.H.; Singhalage, I.D.; Henagamage, A.P.; Seneviratne, G.
    Extensive application of chemical fertilizers and agrochemicals has led to environmental and health issues, and has contributed to climatic changes. In order to minimize the usage of them, environmental friendly biofertilizers containing inoculants of beneficial microorganisms have been introduced. Present study aims in investigating a microbial biofertilizer for tomato, a vegetable highly dependent on the chemical fertilizers (CFs). Bacterial species living in tomato rhizosphere were isolated in Nutrient Agar medium. Growth medium pH, growth in N free Combined Carbon Medium (CCM), phosphate solubilization, indole acetic acid (IAA) production and lettuce seed germination assay were conducted for them and 8 isolates ( J, C, S, F, I, R, B, E) were selected for tomato plant assay. Those isolates were inoculated to soil in tomato planted pots in triplicate. Recommended dosage of CFs for tomato was taken as positive control and a negative control was maintained without adding CFs or microbes. Plant height, number of leaves and flowering were recorded at 10th week and data were analyzed by ANOVA in minitab16.1. The highest clear zone diameter (40 mm) in phosphate solubilization and highest absorbance in IAA were given by isolate C. Inoculants B, R, S changed the colour of CCM into blue, while J, E, I, F, C changed the colour of medium to yellow. In lettuce seed germination assay, the highest vigor and germination percentage were observed in B (246) and F (82%), respectively. All bacterial isolates significantly (p ≤ 0.05) improved plant height over the controls. The highest mean plant heights were observed under bacterial strains C (93 cm), S (91 cm), F (91 cm) and E (90 cm). Plant treated with C showed the significantly increased leaf number per plant over the other species and the controls. Flower number was highest in E and F treated plants. In conclusion, bacterial strains associated with tomato rhizosphere have the potential to be used as biofertilizers to improve the vegetative growth of tomato.
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    Ecosystem Carbon Sequestration of Different Land-uses of the Lowland Wet Zone: A Case Study from Waga Area, Kalutara District, Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2018) Kuruppuarachchi, K.A.J.M.; Madurapperuma, B.D.; Seneviratne, G.
    This study examines plant above-ground carbon and soil carbon stocks of different land-use types with the same climate and geology in Waga area i.e., natural forests (NF), home gardens (HG), coconut plantations (CP), pine and Araucaria mixed plantation forest (PAP), rubber plantation (RP), rambutan plantation (RAP), pineapple plantation (PP) and tea plantation (TP). Five representative sampling sites viz., 20 m x 20 m were selected in each land-use for floristic survey and to make composite soil core sampling (20 samples mixed together) up to a 30 cm depth. Plant parameters, such as DBH, height and physicochemical properties of soil samples were evaluated. The normalized difference vegetation index (NDVI) was calculated using 2017 Landsat 8 image at 30 m spatial resolution, which was acquired during leaf-on season (i.e. mid January to mid March), to recognize the vegetation health. The study revealed ecosystem carbon and soil C densities in the order NF (625 and 52 t C ha-1),PAP (290 and 38 t C ha-1) HG (199 and 21 t C ha-1), RP (188 and 17 t C ha-1), CP (167 and 25 t C ha-1), RAP (167 and 28 t C ha-1), PP (40 and 38 t C ha-1) and TP (15 and 15 t C ha-1), respectively. NDVI values of the land-uses were RP (0.623), HG (0.618), NF (0.615), CP (0.611), PP (0.592), TP (0.576), RAP (0.562), and PAP (0.556). The highest soil moisture accumulation was reported in NF (17.7%) and RP (16.38%). Soil pH values were mainly acidic (< 5) for all land-uses. High total soil N concentrations were observed in both NF (0.18%) and PAP (0.14%). Higher amounts of soil nitrate were recorded in RAP (15.55 𝜇𝑔 g-1 soil), NF (11.45 𝜇g g-1 soil) and PP (9.32 𝜇g g-1 soil). Soil total P concentrations were relatively low in NF (0.041%), PAP (0.042%) and RP (0.045%), and it is an obvious fact for tropical land-uses with perennial vegetation. This study revealed that the land-use types, such as NF, PAP, HG and RP were good carbon reserves in tropical lowland wet zone of Sri Lanka. Further investigations on micro carbon cycles of each land-use are recommended for better understanding of ecosystem carbon footprint.
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    Effect of Biofilm Biofertilizer on Tea Cultivation
    (Uva Wellassa University of Sri Lanka, 2020) Chandralal, R.P.V.T.; Jayasekara, A.P.D.A.; Seneviratne, G.; Herath, H.M.S.K.; Silva, P.D.P.M.; Abeysinghe, D.C.; Premarathna, M.
    In tea cultivation, decreased soil quality can be seen in places where tea has been grown for a long period. Although chemical fertilizers (CFs) release nutrients quickly, they are leached to the deeper layers of soil polluting water bodies. Also, CFs deplete beneficial microbes and insects, thus decreasing plant immunity and soil fertility, causing huge damage to the ecosystem. Biofilm is an assemblage of microbes adherent to each other and/or biotic/abiotic surfaces and embedded in a self-produced extracellular matrix of polymers. In-vitro developed biofilms can be used as biofilm biofertilizers (BFBFs). BFBFs can break the dormancy of microbial forms in the soil, thus enhancing biodiversity, nutrient cycling, plant immunity, and crop production. This study focused on analysing the effects of the BFBF on soil, plant, and microbial parameters. The study consisted of two uniformly managed tea lands in Badulla. The fields were applied with two treatments separately; (a) 100% CF of Tea Research Institute (TRI) recommendation of VPUva 925, and (b) 75% CF of TRI recommendation of VPUva 925 + BFBF 2.5 L ha–1 . All quantitative data were analysed with a two-sample t-test. An increasing trend was observed in endophytic diazotrophs (p=0.08) in BFBF treatment over the growers’ 100% CF practice. Significantly (p≤0.05) higher soil pH, moisture, labile carbon, organic carbon, total nitrogen, leaf total polyphenols (SPAD), made tea production and the amount of soil carbon sequestered was observed in the BFBF practice over the growers’ practice. However, a significant (p>0.05) difference could not be observed for soil available potassium and soil total phosphorous contents. Application of BFBF improved the nutrient utilization efficiency of plants and led to an increase in tea yield over the growers’ practice of CF alone application while cutting down CF usage by 25%. Therefore, it is concluded that the BFBF is an eco-friendly and economically viable method to replace the growers’ current practice of CF alone application. Keywords: Biofilm, Biofilm biofertilizers, Nutrient cycling, Soil fertility
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    Effect of Some Selected Plant Species in Ameliorating Indoor CO2 Concentration
    (Uva Wellassa University of Sri Lanka, 2018) Madumalil, K.A.A.D.; Senaratne, R.; Seneviratne, G.; Lekamge, C.; Wijesundara, D.S.A.
    In view of increasing migration from rural to urban areas and inadequacy of suitable accommodation in towns, many people and students in urban areas live in highly congested, ill-ventilated and abodes. Such conditions have resulted in deterioration of indoor air quality, including increased concentration of CO2 which have posed issues such as Sick Building Syndrome (SBS), reduced productivity and undue fatigue. Therefore, studies were carried out to evaluate the effectiveness of some selected CAM plant species, namely Zamioculcas zamiifolia, Sansevieria trifasciata and Kalanchne spp., in improving indoor air quality. Plants of comparable age and size of the said species were selected and placed in air-tight containers (4500 cm3) one each in 3 replicates. CO2gas (0.1 ml) of 1000 ± 250 ppm was injected into each container and gas samples were collected at the beginning of the experiment (7.00 hours) and at four hourly intervals 11.00, 15.00 and 17.00 hours and were analyzed for CO2 concentration by gas chromatography using a capillary column. Inter-specific variation in CO2 absorption was evident which was highest in Kalanchoe spp. (176.76 ppm.g.hr-1) followed by Zamioculcas zamiifolia (94.94 ppm.g-1.hr-1) and Sansevieria trifasciata (43.16 ppm.g-1.hr-1). Preliminary studies showed a considerable interspecific variation in reducing CO2 concentration in indoor spaces. Therefore, there are prospects for improving indoor air quality of particularly congested and ill-ventilated abodes using plants effective in absorbing elevated CO2, concentration.
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    Effect of using Biofilmed Biofertilizer to Control the Tip Burning and Leaf Spot Diseases of Dracaena sanderiana and Cordyline fruticosa
    (Uva Wellassa University of Sri Lanka, 2016) Udagedara, U.M.C.S.; Kaliyadasa, P.E.; Premathilake, U.G.A.T.; Seneviratne, K.A.C.N.; Seneviratne, G.
    Draceana sanderiana and Cordyline fruticosa are highly demanding cut foliages in foliage industry. Due to its perishable nature in foliage, it is highly susceptible to pest and pathogens which causes loss of appearance and thereby reduce the ornamental value of the plants. Tip Burning, Leaf Spots, Fusarium stem and root rot are some of the major diseases in these plants. High amount of fertilizer and agro chemicals are used to improve the growth of the plants and to control the pest and disease problems. It is an extra cost in floriculture sector and also reduces the quality of the products. Biofilmed Biofertilizer (BFBF) is a cost effective and environmentally friendly bio-fertilizer type. Most importantly it suppresses the pathogens through improved biodiversity and acts as a biological control agent. The research was conducted to identify the possibility of using BFBF to control the Tip Burning and Leaf Spot diseases of Dracaena sanderiana "white", Dracaena sanderiana "gold" and Cordyline fruticosa. Grow More fertilizer was used as the chemical fertilizer in 2.5 g/1 concentration and Biofilmed- F was used in 1: 15 ratio by volume. Five treatments were used namely BFBF alone, full strength chemical fertilizer only, half strength chemical fertilizer only, BFBF with half strength chemical fertilizer and Distilled water as control. The study revealed that the application of BFBF alone is more effective in controlling the Tip Burning and Leaf Spot diseases of Dracaena sanderiana "gold" and Leaf Spots in Dracaena sanderiana "white". Application of BFBF with half strength chemical fertilizer is more effective in controlling both diseases of Cordyline fruticosa and controlling Tip Burning of Dracaena sanderiana "white" when compared to the use of chemical fertilizer alone. In overall, BFBF with half strength chemical fertilizer is more effective in controlling the Tip Burning and Leaf Spot diseases of Dracaena sanderiana and Cordylinefruticosa while promoting a better growth. Keywords: Dracaena sanderiana, Cordyline fruticosa, Biofilmed Biofertilizer, Tip Burning, Leaf Spots
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    Enhancement of Cellulolytic Activity through Biofilm Action for Bioethanol Production
    (Uva Wellassa University of Sri Lanka, 2018) Jayathilaka, M.G.L.W.; Henagamage, A.P.; Peries, C.M.; Seneviratne, G.
    Cellulosic biomass is a biopolymer with great potential for bioconversion to valueadded products. However, efficient degradation of cellulose is a problem in many industries including bioethanol production. Although a variety of microorganisms are capable of degrading cellulose, few of them produce significant quantities of enzyme fractions which hydrolyze cellulose to simple sugars. Extensive studies on bio-degradation by cellulolytic mixed microbial cultures would be beneficial in cellulosic biofuel production. Thus, this study was focused to evaluate the efficiency of cellulolytic activity of mono and mixed microbial cultures. Microbial isolations were carried out using soil samples obtained from a land at Kuliyapitiya, in Kurunegala district, Sri Lanka. They were streaked on Cellulose-Congo red Agar medium to screen for potential cellulolytic microorganisms. The selected microorganisms were inoculated on Carboxy Methyl Cellulose Agar medium to screen the most effective cellulolytic fungi and bacteria. Fungal-bacterial biofilms (FBB) were developed from the selected cellulolytic fungi and bacteria using Combine Carbon Broth. The efficiency of cellulolytic activity of the selected microbial combinations was evaluated using the production of reducing sugar through 3,5-Dinitro Salicylic acid after treating with cellulose powder. Two fungal (F1 and F2) and three bacterial isolates (B1, B2 and B3) were selected as the best cellulolytic microorganisms. Out of the selected cellulolytic microorganism, F2 and B I showed the significantly highest cellulolytic activities (P < 0.05). This mean reducing sugar level (113.90 ppm) was observed with the F2B1 combination after twenty three days of incubation. In addition, F2, B1 and B2 mono cultures showed significantly higher yield of reducing sugar than that of the other mono and mixed cultures, except F2B1. Thus, the selected FBB combination can be used to enhance the hydrolysis efficiency of cellulose for bioethanol production.
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    Modification of Nutrient Agar Medium to Culture Un-culturable Bacterial Strains Living in Unsanitary Landfills
    (Uva Wellassa University of Sri Lanka, 2020) Devika, K.K.C.; Singhalage, I.D.; Seneviratne, G.
    The decomposition of municipal solid waste is mediated by native microorganisms and it is essential to estimate the participating microorganisms to accelerate the decomposition of waste material. However, 99% of bacterial species remain unculturable in the standard Nutrient Agar (NA) medium. This research was focused on the modification of the NA medium to mimic the composition of the natural substrate where they live. Conventional NA medium was modified by adding separately 40% (M1), 32% (M2), 24% (M3), 16% (M4), 8% (M5) (v/v) of soil extracts obtained from the dumpsite. The Conventional NA medium was the control. Random soil samples were collected from the garbage dump and bacterial species were isolated in each modified medium. The isolated bacterial cultures were air-dried under aseptic conditions and powdered. To characterize them, Fourier Transform Infrared (FTIR) spectra were recorded for all bacterial samples in the 500 - 4000 cm-1 region at 4 cm-1 resolution by scanning 120 times. The average of the absorbance of each FTIR spectrum was used as variables of the distance matrix of the cluster analysis (Minitab 19). A total of 103 bacterial strains were isolated and 9 bacteria samples showed a similarity level of more than 98%. The 20, 14, 16, 16, 18, and 19 bacteria species were isolated from the modified media M1, M2, M3, M4, M5, and the control, respectively. According to the cluster analysis, six clusters were obtained. Cluster 1 was the largest and it consisted of 45.63% of the total bacterial isolates from M1, M2, and the control. Cluster 2 consisted of 30.10% of total isolates from M4-M5. All the other isolates were clustered in clusters 3, 4, and 5. The separate clustering of the isolated bacteria in the modified media showed dissimilarity among them, thus indicating the potential of the soil extracts to modify NA to culture un-culturable bacterial strains living in unsanitary landfills. Keywords: Unculturable bacteria, Soil extracts, FTIR
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    Potential of Biofilm Biofertilizer Application in Paddy Soil Carbon Sequestration in Sri Lanka: An Economic Feasibility Analysis
    (Uva Wellassa University of Sri Lanka, 2020) Ekanayake, S.N.B.; Seneviratne, G.; Premarathna, M.; Gunathilaka, R.P.D.; Banagala, C.H.M.; Hearth, H.M.S.K.
    Anthropogenic emissions of carbon (C) to the atmosphere at higher rates have led to global warming and climate change. Soil carbon sequestration (SCS) has been recognized as the process that stores atmospheric C for a long period without escaping back to the atmosphere. Globally, expanding agricultural lands has come to play a major role in SCS in the phase of degradation of natural ecosystems like forests by deforestation, fire, etc. The objective of this study was to evaluate the potential of Biofilm biofertilizer (BFBF) application in SCS under rice cultivation. Soil stable C was estimated as sequestered soil C by using organic carbon (Walkley-Black) and oxidizable carbon in the BFBF application and the farmers’ chemical fertilizer (CF) alone application. Soil samples were collected from paddy fields in 25 representative locations in several districts of Sri Lanka in three consecutive seasons: Yala 2018, Maha 2018/19, and Yala 2019. The results showed that the SCS was significantly (p<0.05) higher in the BFBF practice in every season. This is due to increased microbial C assimilation in the root zone of soil. The BFBF practice sequestered 19 t C ha-1 year–1 over farmers’ CF practice, showing an enormous potential to gain income through soil C trading. There was also an increasing trend in the paddy grain yield up to ca. 30% under the same practice. Thus, during the next five years, if the BFBF practice would be implemented island wide, the potential income from trading C will be ca. 190 billion rupees. In conclusion, the BFBF practice can be considered as an eco-friendly and economically viable method to replace the farmers’ current practice of CF alone application. Keywords: Biofilm biofertilizer, Carbon trading, Rice cultivation, Soil carbon sequestration