Pretreated water hyacinth was used as sole carbon source for the production of cellulase enzyme by Rhizopus oryzae PR 7 MTCC 9642 in both liquid state (LSF) and solid state fermentation (SSF) that was measured by the FPase activity. To maximize the FPase production, the critical parameters like substrate concentration, cultivation temperature and pH on enzyme production were optimized using response surface methodology using Central Composite Design (CCD). The LSF was found to be better than SSF for the production of FPase. The best preferred combination for highest FPase activity from LSF was with substrate concentration 1.25%,pH 7.32 and temperature 25.25°C. Estimated optimum conditions for FPase production from SSF was a combination of substrate concentration of 0.5%, pH 6, temperature 18°C. Under the optimized cultivation condition, the strain synthesized 123 U/ml and 48U/ml FPase from LSF and SSF respectively and the highest production was achieved within only 48 hours of cultivation.