Abstract: Ethanol is produced from water hyacinth, an aquatic weed plant, comprising of cellulose, hemicelluloses and lignin by a two-step method. Water hyacinth was pretreated with different concentration of sulfuric acid, detoxified with CaOH and NaOH and then fermented using Zymomonas mobilis CP4 (a recombinant strain). Batch fermentation and Simultaneous Saccharification and Fermentation (SSF) were performed and the ethanol yields were compared. Central Composite Design (CCD) is conducted to optimize the production conditions like pH, temperature, enzyme concentration and substrate concentration for higher ethanol yield. Under optimum conditions ethanol yield was found to be 68.3 g L-1.