http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/72 2026-07-18T02:20:24Z 2026-07-18T02:20:24Z Thavarasa, M. Shayanthan, A. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/12742 2026-07-17T09:14:41Z 2026-01-01T00:00:00Z

Isolation and characterization of bacteria from paddy (Oryza sativa) fields Thavarasa, M.; Shayanthan, A. Paddy (Oryza sativa) cultivation is integral to Sri Lanka's agriculture, as rice is the staple food of the country. Wide variety of microorganisms are in the Paddy Jaffna, Sri Lanka rhizosphere which play an important role on paddy growth and soil fertility. Modern paddy cultivation heavily relies on chemical fertilizers, which degrade soil health and productivity. This study was conducted to isolate and characterize plant growth-promoting rhizobacteria from local paddy fields. Soil samples were collected from Vaddakachchi Ramanathan farm and Paranthan rice research station in Kilinochchi district. Through serial dilution and plating in nutrient agar medium, 24 distinct bacterial isolates were obtained. Purified isolates were subjected to functional characterization for nitrogen-fixing ability, phosphate-solubilization ability, and plant growth promotion using a seed germination assay. Results revealed that isolate B1 showed significantly highest nitrogen fixing ability, followed by B8, A5, and A2. The phosphorus solubilization ability is less in all the strains and ranged below 1ppm. The seed germination test revealed that bacterial inoculation positively influenced paddy seed germination and seedling growth. The bacterial isolates B1, B8, B14, A2, and A5 showed higher seed germination percentage and vigour index compared to the control. Therefore, isolates B1, B8, A2 and A5 have the potential to be used as biofertilizers to improve crop productivity. This study indicates the potential of indigenous soil bacteria in enhancing plant growth-promoting traits. Further studies are needed to explore other plant growth-promoting traits and validate their effect in field conditions.

2026-01-01T00:00:00Z Jayasekara, I.R.N.D. Sivakanthan, S. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/12738 2026-07-07T04:27:33Z 2026-01-01T00:00:00Z

Evaluation of the effect of passion fruit (Passiflora edulis) leaf extract on the oxidative stability of palm oil during heating Jayasekara, I.R.N.D.; Sivakanthan, S. The growing need for natural alternatives to synthetic antioxidants in edible oils has driven extensive research into plant-derived extracts for enhancing oil stability during thermal processing. This study was carried out to evaluate the effect of continuous heating on the quality of palm oil and to assess its oxidative stability during heating by adding passion fruit leaf extract as an antioxidant. Acetone was used as the solvent to extract antioxidant components from fresh leaves with a sample to solvent ratio of 1:10 (w/v). Negative control (oil samples without any added antioxidants), positive control (oil sam-ples added with 200 ppm of Butylated Hydroxytoluene (BHT) and test samples (oil samples added with 1000 ppm of leaf extract) were prepared. All oil samples were evaluated for stability under continuous heating at 170±5 °C. Continuous heating was carried out for up to 24 h (30 min heating followed by 30 min cooling), that is, 24 heating cycles. Sampling was done at 2 h intervals (after every 2 heating cycles). The levels of oxidation of the samples were determined by evaluation of peroxide value, p-anisidine value, TOTOX value, free fatty acid content, total polar compounds, fatty acid composition and conju-gated diene (CD) and conjugated triene (CT) values. All parameters measured were increased in all three samples; however, free fatty acid content, peroxide value, p-anisidine value and CD and CT values were significantly less in the test samples than in the positive control and negative control. The average rate of total polar compound formation, expressed as the percentage increase per heating cycle, was significantly lower in extract-treated (1.29% per cycle) and positive control (1.27% per cycle) samples than in the negative control (1.68% per cycle). These results indicate that the sample supplemented with passion fruit leaf extract exhibited higher thermal stability than both controls, and that fresh leaf extract (1000 ppm) more effectively controls the thermal oxidation of palm oil than BHT during continuous heating.

2026-01-01T00:00:00Z Thurkka, S. Kirisan, A. Gnanavelrajah, N. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/12734 2026-06-30T04:42:07Z 2026-01-01T00:00:00Z

Nitrification Inhibition by Karanja (Pongamia glabra Vent) Seed Powder and Its Extract Thurkka, S.; Kirisan, A.; Gnanavelrajah, N. Nitrification inhibitors are applied to slow down the conversion of ammonium to nitrate, which will enhance nitrogen availability to crops, and nitrogen use efficiency in farming systems by reducing nitrogen losses. This study aimed to assess the nitrification inhibition potential of Karanja (Pongamia glabra Vent) seed powder and its extract. The experiment comprised three phases: incubation study, leachate study, and microbial study, with seven treatments -T1 (Soil), T2 (Soil + Urea), T3 (Soil + Urea + 5% Neem oil), T4 (Soil + Urea + 10% Karanja extract), T5 (Soil + Urea + 20% Karanja extract), T6 (Soil + Urea + 10% Karanja powder), and T7 (Soil + Urea + 20% Karanja powder). Baseline soil properties included pH 6.58, EC 67.73 μS/cm, CEC 67.36 cmol (+)/kg, phosphorus 12.46 ppm, potassium 228.07 ppm, and total nitrogen 0.023%. Karanja powder and Karanja extract contained 0.313% and 0.014% nitrogen, respectively. According to the incubation study the highest nitrification inhibition % was found in T3 (52.4%) followed by T5 (49.8) and T4 (46.2). Treatments T6 and T7 (Karanja powder) exhibited no significant inhibition. Leachate study showed a significant reduction in nitrate leaching loss in T3, T4 and T5 compared to T2, T6 and T7. Microbial analysis confirmed the inhibition by Karanja extract, supporting its role as an effective nitrification suppressor. The study concludes that Karanja extract and neem oil are potent natural nitrification inhibitors, while Karanja powder alone is ineffective in this regard. Further studies under field conditions are suggested to verify the results.

2026-01-01T00:00:00Z Taniya, A.K. Vasantharuba, S. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/12733 2026-06-30T04:35:42Z 2026-01-01T00:00:00Z

Effect of Different Drying Methods on Nutrient Retention Characteristics of the Pearl Millet- based Functional Food Supplement Ingredients Taniya, A.K.; Vasantharuba, S. The development of functional foods requires careful selection of processing conditions that preserve the nutritional quality of raw materials while ensuring their suitability for formulation and storage. Cereals and legumes such as pearl millet (Pennisetum glaucum), green gram (Vigna radiata), and peanuts (Arachis hypogaea) are nutritionally rich; however, their macro and micronutrient content is susceptible to degradation during thermal processing. Therefore, identifying ingredient-specific processing conditions is essential. This study evaluated the effects of Low Temperature Long Time (LTLT) and High Temperature Short Time (HTST) processing on selected raw materials to identify the most suitable condition for nutrient retention and functional food application. Pearl millet, green gram, and peanuts were cleaned and processed under controlled LTLT and HTST conditions, followed by drying and grinding. The processed samples were compared with raw materials to assess the influence of thermal treatment on nutritional stability. The findings indicated clear ingredient dependent responses to processing conditions. Moisture content, expressed on a wet basis, decreased substantially after processing and was approximately 2-8%, indicating suitability for storage. Protein content of green gram and peanuts remained relatively stable under both processing conditions, with values in the range of 22-26% for green gram and 25-30% for peanuts. HTST processing resulted in greater moisture reduction in these two ingredients, suggesting improved shelf-life potential. In contrast, pearl millet exhibited higher protein retention under LTLT processing, with protein values of 10-13%, whereas HTST- treated pearl millet showed reduced protein levels of approximately 5-8%, indicating greater sensitivity to high-temperature exposure. Carbohydrate content remained within expected ranges for cereals and legumes (approximately 60-70%), with only marginal variation between processing conditions. Overall, the results confirm that HTST processing is suitable for green gram and peanuts, while LTLT processing is more appropriate for pearl millet, emphasizing the importance of ingredient-specific thermal processing strategies in functional food development.

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