Abstract:
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
