1,720,958 research outputs found
Antifungal Activity of Selected Indigenous Medicinal Plants in Sri Lanka Against Candida Infections
Get PDFCandida infections have been recorded as an emerging health concern among immune- compromised patients, infants and pregnant women in Asia, Africa and Europe. Skin diseases, genital infections, candidiasis and candidemia caused by overgrowth of symbiotic Candida species in the human body are treated by antifungal drugs. The common drugs viz., fluconazole, flucytosine, amphotericin B, nystatin, etc. are responsible for more side effects in the human body while Candida species are indicating a resistance towards them. Therefore, the continuous discovery of antifungal compounds against Candida infections is an essential process. Thus, the current study focused on the determination of the antifungal activity of water extracts of selected indigenous medicinal plants in Sri Lanka towards Candida infections. Three common indigenous medicinal plants; Cyperus rotundus (roots, tubers, leaves and flowers), Acalipha indica (roots, stem, leaves and flowers) and Aloe barbadensis Miller (gel and leaves) were collected and their water extracts (10 g/25 mL) were screened for the antifungal activity against two common Candida species; Candida glabrata and Candida parapsilosis using disk diffusion method. Briefly, the pathogenic bacterial lawns were prepared by spreading equalized solutions of C. glabrata and C. parapsilosis on Muller Hinton Agar supplemented with 2% glucose. Sterile paper disks soaked with 30 µL of water extracts of each plant part were placed on pathogen lawns. Sterile distilled water was used as the negative control. The plates were incubated at 37° C overnight and observed for clear zone formation. According to the results, the water extract of C. rotundus tubers indicated an inhibitory action by giving clear inhibition zones against both tested Candida species. All other water extracts of medicinal plants indicated negative inhibitory actions against tested Candida species. The results revealed that C. rotundus tubers consist of antifungal activity against C. glabrata and C. parapsilosis. Hence, C. rotundus tubers can be used as an effective treatment for infections caused by the tested Candida species.
Keywords: Antifungal activity, Candida infections, Indigenous medicinal plants, Cyperusrotundus, Water extracts
 
Isolation of Salt-Tolerant Enzyme-Producing Bacteria from Marine Environments in Sri Lanka for Industrial Applications
Get PDFMicrobial enzymes have been used in our day-to-day lives since ancient times. In the current world, microbial enzymes are widely used in industries owing to their environmentally friendly nature and cost-effectiveness. Halophiles are industrially important bacteria due to their high stability in high salt concentrations. Amylases, cellulases, proteases and lipases are the most widely used halophilic hydrolytic enzymes in food production, detergent industry, pharmaceutical industry, biofuel production, paper production, etc. Each of these enzymes plays a vital role in industrial production. Thus, the current study focused on the isolation of salt-tolerant enzyme-producing bacteria from marine environments in Sri Lanka for industrial applications. The water samples were collected from Negombo Lagoon and Panadura Beach in Sri Lanka and transported to the laboratory in ice boxes. Subsequently, the water samples were enriched in quarter-diluted Nutrient Broth (NB) medium. The morphologically different bacteria isolates were isolated by the standard spread plate method. All isolated bacterial isolates were screened for the production of amylase, cellulase, protease and lipase using Starch Agar, CMC agar, Skimmed Milk Agar and Phenol Red Agar plate assays respectively. Then, the growth temperature and salt concentrations for enzyme-producing bacteria were optimized. A total of morphologically different 44 bacterial colonies were isolated from both sample sites 25 bacterial colonies from the Negombo Lagoon sample and 19 bacterial colonies from the Panadura Beach sample. A total of 21 bacterial isolates were positive for amylase production 3 from Negombo lagoon and 18 from Panadura beach samples while 26 bacterial isolates were positive for cellulase enzyme 9 from Negombo lagoon and 17 from Panadura beach samples. Moreover, 15 out of 25 bacterial colonies isolated from the Negombo lagoon sample were positive for Protease enzyme while only 5 colonies from the Panadura beach sample were positive for protease. A total of 22 bacterial isolates were positive for amylase production 14 from Negombo Lagoon and 8 from Panadura beach. As a whole, almost 95% of isolated bacteria were positive for at least one enzyme activity. As per the results, the optimum growth temperature was recorded in a range of 300 C to 350 C while the optimum growth was reported in a range of 3% to 12% of NaCl concentration. Thus, marine environmental bacteria can be considered as a potential halophilic enzyme producer and may be utilized in industrial settings successfully. Further studies are in progress to determine the optimum conditions for enzyme activity.
Keywords: Halophiles, Halophilic bacteria, Industrial applications, Marine bacteria. Enzyme producing bacteri
Industrial Perspective of Thermo-Stable Proteinase Enzyme Producing Bacteria Isolated from Maha Oya Hot Spring, Sri Lanka
Get PDFThe microbial enzymes are eco-friendly and cost-effective alternatives for chemical catalysts that adversely affect the ecosystem. Among the commercially available enzymes, proteases are the most demanded enzyme and contributes nearly 60-65 % of the world enzyme market. Therefore, this study aimed on isolation and characterization of thermo-stable proteinase producing hot spring bacteria. For the present study, water samples were collected from surface and bottom of Maha Oya hot springs. Temperature, Electrical Conductivity (EC), pH, and Dissolved Oxygen (DO) were measured at the site. The standard pour plate method was performed to isolate bacteria and primarily screened for proteinase production by Skimmed Milk Agar (SMA) plate assay. Secondary screening was performed using the Folin-Ciocalteu’s Phenol reagent method. Optimum temperatures and pH for enzyme activity were measured for crude enzyme extracts of most potential candidates. Molecular-level identification of bacterial isolates was performed using the 16S rRNA gene sequencing method. Briefly, genomic DNA was extracted from pure bacterial isolates and PCR amplification of V3 and V4 regions of 16S rRNA gene was done using 27F and 1492R bacterial domain specific primers. Then, the DNA sequencing was done at Macrogen, Korea. The resulted sequences were aligned with available sequences at NCBI using BLASTn tool and GenBank accession numbers were obtained. Temperature, EC, pH, and DO of the surface and bottom of the springs varied from 51.7-52.4º C, 1487-1,507 µS/cm, 8.05-8.07, and 2.01-2.05 mg/L respectively. Three morphologically different, proteinase producing bacterial isolates were observed (Mh11, Mh12 and Mh27) at the primary screenings and bacterial isolate: Mh11 which was identified as Bacillus cereus strain VBE03 (Accession number: ON819722) showed the highest enzyme activity of 209.205 U/mL at optimum temperature of 60º C, and optimum pH of 9. Hence, the bacterial isolate: Mh11 would be successfully used for industrial settings operate at temperatures around 60º C and alkaline conditions.
Keywords: Hot springs, Enzymes, Proteinase, Biotechnology, Thermophile
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Characterization of Thermostable Cellulase Enzyme Isolated from a Hot Spring Bacterium: Bacillus sp.
Get PDFCellulase is a complex of enzymes which consists of β-1,4-endoglucanase, cellobiohydrolase, and β-glucosidase. Cellulase contributes a significant share to the world enzyme market and is used in number of industries viz; paper and pulp, food and beverage, bioethanol, detergent and textile. The harsh industrial conditions such as high temperature, extreme pH levels and high substrate concentration etc. which is used in such industries adversely effect on structure and activity of enzymes. Therefore, huge amount of chemical catalysts which cause chemical wastes are used in industrial settings instead of enzymes. Since the chemical wastes adversely affect the ecosystem, isolation and characterization of thermostable cellulase enzyme-producing bacteria and exploring the industrial perspective of thermostable enzymes is a better approach towards green chemistry. The present study focused on characterization of cellulase enzyme produced by Bacillus sp., which shows optimum activity at 60 C under neutral conditions, isolated from Gomarankadavala hot spring in Sri Lanka. The effect of different Carbon sources: glucose and lactose, Nitrogen sources: peptone, tryptone, yeast extract and urea on enzyme production and different Carboxymethylcellulose (CMC) concentrations; 0.5%, 1.5% and 2%, on enzyme activity were measured using the DNS method. Under the optimum conditions, cellulase enzyme activity on different substrates: corn cob, rice bran and raw leaves were measured. The highest enzyme production was recorded in the culture medium which added tryptone as the nitrogen source and adding carbon sources to the culture medium showed an increase of cellulase enzyme production. The optimum CMC concentration for the enzyme activity was recorded as 1% and from all the optimized parameters, the substrate; raw leaves showed the highest enzyme activity of 11.305 U/ml. Further, a considerable amount of enzyme activity was recorded on corn cobs and rice bran as well. Thus, the thermostable cellulase enzyme produced by bacterium identified as Bacillus cereus isolated from Gomarankadavala hot spring could be successfully used in industrial settings such as kitchen/industrial waste management, bioethanol production, paper and pulp industry and textile industry which use high temperatures and cellulosic substrates as raw materials.
Keywords: Thermostable enzymes, Cellulase, Industrial applications, Hot springs 
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Isolation of Endophytes with Antimicrobial Activity from Selected Indigenous Medicinal Plants Against Amoxicillin-Resistant Environmental Bacteria
Get PDFThe continuous discovery of novel antimicrobial compounds and antibiotic-producing microorganisms is an obligatory process to overcome the antibiotic resistance of pathogenic bacteria that arises as a consequence of the misuse of antibiotics. Thus, this study is mainly focused on the isolation of endophytic bacteria and fungi with antimicrobial activity against amoxicillin[1]resistant environmental bacteria. The endophytes were isolated from the selected indigenous medicinal plants, namely Acalypha indica (Kuppameniya) and Cyanthillium cinereum (Monarakudumbiya). Fresh samples of the selected plants were collected from their natural habitats, and the plant parts were surface-sterilised using 70% ethanol. The endophytic bacteria and fungi were then isolated on Nutrient Agar (NA) and Potato Dextrose Agar (PDA) media respectively at room temperature. The isolated endophytic bacteria and fungi were screened for their antimicrobial activity against four previously isolated amoxicillin-resistant environmental bacteria, namely Acinetobacter baumannii, Staphylococcus aureus, E. ludwigii and E. pyrinus. As per the results, a prominent inhibition of Staphylococcus aureus was shown by four endophytic isolates (KpR-02B, MnS-01B, KpS-01F and MnR-04F). The AR bacteria E. ludwigii was prominently inhibited by two endophytic isolates (MnS-01B and MnR-04F), while E. pyrinus was also prominently inhibited by two endophytic isolates (MnF-03B and MnR-04F). Thus, the indigenous medicinal plants, Kuppameniya and Monarakudumbiya, can be considered as a potential source of antimicrobial compound-producing endophytes against amoxicillin-resistant environmental bacteria, which can be developed as a drug for antibiotic-resistant pathogenic bacteria.
Keywords: Antimicrobial activity, Antibiotic-resistant bacteria, Indigenous medicinal plant
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