Graphene oxide (GO) treated thermostable crude cellulase has been obtained via fungal co-cultivation of strain Cladosporium cladosporioides NS2 and Emericella variecolor NS3 using mix substrate of orange peel and rice straw under solid state fermentation (SSF). Enzyme activity of 60 IU/gds FP, 300 IU/gds EG and 400 IU/gds BGL are recorded in the presence of 1.0% GO in 96 h. This crude enzyme showed 50 degrees C as optimum incubation temperature, thermally stable at 55 degrees C for 600 min and stability in the pH range 4.5-8.0. Further, 70.04 g/L of sugar hydrolyzate is obtained from enzymatic conversion of 3.0% alkali pre-treated baggase using GO treated crude cellulase. Finally, 2870 ml/L cumulative biohydrogen production having bacterial biomass similar to 2.2 g/L and the complimentary initial pH 7.0 is recorded from sugar hydrolyzate via dark fermentation using co-culture of Clostridium pasteurianum (MTCC116) and a newly isolated Bacillus subtilis PF_1.