Browsing by Author "Yogarajah, K."

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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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    Determination of Pectinase Activity of Selected Bacterial and Fungal Strains
    (Uva Wellassa University of Sri Lanka, 2021) Yogarajah, K.; Singhalage, I.D.
    Enzymes have been utilized to speed up the biological reactions in industrial productions. Enzymatic methods are environmentally friendly, low cost in production and disposal but the limitation of sources to extract different enzymes is an issue. Therefore, the current research aimed in order to determine the pectinase activity of selected bacterial and fungal strains isolated from a municipal garbage dump. Thirty-four bacterial (B1–B34) and five fungal (F1-F5) strains taken from the culture collection were activated in Nutrient Agar (NA) and Potato Dextrose Agar (PDA) respectively. For the enzymatic assay, the bacterial and fungal strains were re-cultured in NutrientBroth (NB) and Potato Dextrose Broth (PDB) respectively. The culture medium collected on day four was centrifuged and cell free supernatants were then tested for pectinase activity by well diffusion assay conducted in Pectinase Screening Agar medium (PSA) by following the Complete Randomized Design with three replicates. The NB alone was the control. Diameters of halo zones formed around the wells were measured at day four as the data. Data were analyzed by one way ANOVA. The bacterial culture, B16 showed the highest pectinase activity among bacterial strains. F3 showed significant (p ≤ 0.05) pectinase activity among fungal strains. The study was further elaborated to find out the optimal maturity stage of B16 and F3 with the highest pectinase activity. For that, B16 were re-cultured in NB and F3 was re-cultured in PDB. The crude enzyme was extracted from the subsamples collected from each medium within 6 hr time intervals and used to digest pectine and the amounts of sugar formation after the pectine digestion was evaluated by DNSA method. The B16 showed highest pectinase activity (2.95 AU) at 72 and 78 hours of inoculation whereas F3 showed the highest pectinase activity (1.43 AU) between 54 and 78 hours of inoculation. Thus, the pectinase activity of B16 is higher than that of F3. Therefore, B16 of present study can be introduced as an efficient culture to extract pectinase enzyme in bulk for industrial applications. Keywords: Bacteria; Fungi; Pectinase