http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/5660 2026-04-07T14:38:36Z 2026-04-07T14:38:36Z Keerthini, S. Kapilan, R. Vasantharuba, S. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/2428 2022-10-21T07:42:03Z 2017-01-01T00:00:00Z

Title: Isolation of potential bacteriocin-producing lactic acid bacteria from fermented food products showing antimicrobial activity Authors: Keerthini, S.; Kapilan, R.; Vasantharuba, S. Abstract: Biopreservation systems in foods are gaining popularity in food industries. Bacteriocins, an antimicrobial peptide produced by lactic acid bacteria, is considered as safe additives. Therefore, this study aimed to isolate bacteriocin-producing lactic acid bacteria from selected natural fermented food products with wide spectrum antimicrobial activity. Lactic acid bacteria were isolated from yoghurt, curd, dosa batter, idli batter and rice batter using de Man, Rogosa and Sharpe (MS) agar and incubated at room temperature (30±2 °C) for 24-72 h aerobically and anaerobically. Agar well diffusion method was employed to detect the antimicrobial activity of isolates against food spoilage organisms (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Serratia marcescens, Salmonella sp., Proteus sp., Micrococcus sp., and Bacillus sp.). Antimicrobial activity screening by agar well diffusion assay showed that isolate C3 from curd sample inhibited wide range of bacterial species. Therefore, that wide spectrum bacterium was subjected to diverse cultural, biochemical and morphological studies such as colony morphology, gram staining, catalase test and motility test and identified as Lactobacillus sp. Further studies are under way to purify and characterize the bacteriocin and to confirm whether the selected strain could be used to produce bacteriocin to preserve the food at industrial level.

2017-01-01T00:00:00Z Iddamalgoda, H.K.S.P.S. Hemachandra, C.K. Rodrigo, W.W.P. Fonseka, W.R.K. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/2425 2022-10-21T07:41:59Z 2017-01-01T00:00:00Z

Title: Isolation and morphological characterization of petroleum crude oil degrading bacteria from contaminated sites in Sri lanka Authors: Iddamalgoda, H.K.S.P.S.; Hemachandra, C.K.; Rodrigo, W.W.P.; Fonseka, W.R.K. Abstract: The objective of the present study was to isolate petroleum hydrocarbon degrading indigenous bacteria from chronically contaminated sites. Sludge and water samples collected aseptically from an area (Gampaha district) subjected to chronic discharges of petroleum hydrocarbons were separately inoculated into Bushnell Haas minimal (BHMS) salt broth amended with 2% filter sterilized Murban light crude oil. Cultures were incubated at 28 o C for seven days as the primary enrichment along with an un inoculated BHMS broth as the control. Crude oil was used as the model petroleum hydrocarbon and sole source of carbon and energy. After five successive enrichment cycles, six pure cultures of bacterial isolates were obtained from the discrete colonies observed in the spread plates. The isolated bacteria were grown on BH agar amended with crude oil and nutrient agar (NA) medium. Colony morphological characterization based on colour, size, form, texture, elevation and opacity and Gram staining were performed on bacterial cultures grown on both media. Two of the isolates were Gram positive while other isolates were Gram negative. The ability to degrade crude oil was assessed by inoculating the bacterial isolates into BH culture broths amended with crude oil. The observations showed different degrees of disintegration of crude oil layers through visual observations as well as different degrees of growths through OD620 measurements over a seven day period of incubation at 28 o C. Three isolates showed relatively high growth while other three isolates showed a comparatively lower growth as indicated by OD620 measurements. The three isolates that showed higher growth capacities have a higher potential to utilize crude oil as the sole source of carbon and energy and thus, may be employed for the bioremediation of contaminated sites. However, the species should be subjected to molecular identification and the respective crude oil degradation capacities should be further studied.

2017-01-01T00:00:00Z Kaushalya, W.H. Hemachandra, C.K. Rodrigo, W.W.P. Fonzeka, W.R.K. Samarasekera, R. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/2422 2022-10-21T07:41:22Z 2017-01-01T00:00:00Z

Title: Isolation and morphological characterization of glyphosate utilizing fungi from contaminated sites in Sri lanka Authors: Kaushalya, W.H.; Hemachandra, C.K.; Rodrigo, W.W.P.; Fonzeka, W.R.K.; Samarasekera, R. Abstract: The use of synthetic pesticides has become an indispensable tool in Sri Lankan agriculture. The extreme usage of glyphosate herbicide over the past years in the country has led to a serious environmental pollution. Thus, bioremediation is the most environmentally sound technology for clean-up. This study was aimed at isolation and morphological characterization of the fungal species that could potentially utilize glyphosate as their sole source of carbon and energy. Soil samples were obtained from the selected agricultural lands in Dambulla and Rathnapura area, which were chronically contaminated over ten years with numerous pesticides including glyphosate. The enrichment culture technique was used to isolate fungi from the collected soil samples by providing glyphosate at the concentration of 50 ppm in the Mineral Salts Medium (MSM) under the incubation temperature of 30 o C for two weeks. After 5 enrichment cycles, single fungal species (D1FW) was isolated that could potentially biodegrade glyphosate. D1FW isolate was characterized by culturing on both Potato Dextrose Agar medium and on MSM agar enriched with glyphosate (50 ppm). It was observed that the colony morphology of the fungus grown on the two different media is different. Further, Lacto Phenol Cotton Blue staining conducted under the sticky tape method showed that the DIFW is possessed with small round shaped spores and branched non septate mycelia. Further, the glyphosate utilization patterns based on their growth kinetics over a 7 day period of incubation of the isolated fungus was also assessed. The results revealed more or less a continuous growth in the MSM. In conclusion, the isolated fungal species has the capacity to utilize glyphosate as the sole carbon and energy source and might be used in bioremediation of glyphosate-contaminated environments. However, molecular characterization would be needed for the precise identification of the isolate.

2017-01-01T00:00:00Z Croos, A.M.B. Kapilan, R. http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/2420 2022-10-21T07:41:25Z 2017-01-01T00:00:00Z

Title: Isolation and identification of a cellulase producing bacterial strain Authors: Croos, A.M.B.; Kapilan, R. Abstract: Cellulolytic organisms could be isolated from diverse natural sources and the best bacterial candidate could be used to produce cellulase. The objective of the study was to isolate a thermostable alkaline cellulase producing bacterial strain from diverse natural sources. The samples obtained from multiple sources such as goat excreta, cow dung, tropical soil, and organic matters. Opened hot cellulose agar plate were transferred on to the selective CMC agar media and incubated for 2 days at 37 °C. The samples were cultured on Nutrient Agar in order to isolate cellulolytic bacteria. Bacteria isolated were screened for cellulolytic activity using serial dilution and pour-plate method after which they were characterized. The bacterial isolate showing highest carboxymethylcellulose (CMC) hydrolytic capacity was obtained from cow dung and used for further studies. Based on the morphological, biochemical and cultural analysis, the strain from cow dung was confirmed as Bacillus sp. Pure culture of this bacterial strain was grown overnight for DNA extraction and 16S rDNA was amplified by a Thermocycler using universal primers. When the amplified 16S rDNA PCR product was sequenced using automated sequencer and sequence similarity search was done for the 16S rDNA sequence using BLAST. BLAST in search resulted unknown organism and confirmed as Bacillus cereus in comparison with the GeneBank accession no AF290555. This thermostable alkaline cellulase producer was the best strain and further studies are underway to improve the strain and to optimize the fermentation medium and culture conditions to increase the cellulase production.

2017-01-01T00:00:00Z