Cellulase activity assay

1. Prepare isolate appropriate minimal defined media with the addition of 1% carboxy methyl cellulose and 0.1 % of yeast extract.
2. Inoculate a single isolated colony to isolate appropriate liquid rich media.
3. Incubate for 48 h at 25^o^C with shaking.
4. After incubation adjust culture to OD~600nm~ 0.1
5. Place 4-5 ul drops of adjusted culture in four quadrants of PKA plate, spaced equidistant from each other.
   • NOTE: Unless unavoidable, do not inoculate different isolates onto the same plate.
6. Incubate at 28^o^C for up to 5 days
   • Incubation timing is dependent on isolate growth rate
7. After incubation, flood plates with 0.01% Congo red and stain for 15 min.
8. Decant Congo red solution and flood plate with 1% NaCl and de-stain for 5 min
9. Observe for clearing zones around colonies
10. Measure and record diameter of clearing zones

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Citations

• Cattelan et al 1999 Screening for Plant Growth–Promoting Rhizobacteria to Promote Early Soybean Growth
• Goswami and Deka 2020. Isolation of a novel rhizobacteria having multiple plant growth promoting traits and antifungal activity against certain phytopathogens
• Cappuccino, J.G. and Sherman, N., 1992. Biochemical activities of microorganisms. Microbiology, A Laboratory Manual. The Benjamin/Cummings Publishing Co. California, USA, pp.188-247.