**4.1 Screening method for cellulase producing bacteria**

Screening of bacteria that can produce cellulase can be done using CMC (Carboxymehylcellulose) medium. CMC is a cellulose derivative which is commonly used as a thickener or stabilizer in the industrial field [19]. The composition of the CMC medium includes CMC, yeast extract, MgSO4, NH4H2PO4, and KCl. Bacteria that are thought to be able to produce cellulase are cultivated first on CMC agar medium, under certain conditions. The growth of bacterial colonies on CMC medium can be an early marker of cellulase activity in bacteria. Qualitative confirmation of cellulase activity in bacteria can be done by testing 1% Congo Red and 1 M NaCl. The formation of a clear zone that occurred around the bacterial colony after testing the Congo Red can be used as a qualitative positive result of cellulase activity in bacteria. The formation of this clear zone indicates that bacteria can hydrolyze cellulase contained in the medium to simple sugar (glucose) [18].
