AbstractThe fast growing aquatic weed water hyacinth, which is available almost year-round in the tropics and subtropics, was utilized as the chief source of cellulose for production of fuel ethanol via enzymatic hydrolysis and fermentation. Fungal cellulases produced on-site by utilizing acid-alkali pretreated water hyacinth as the substrate were used as the crude enzyme source for hydrolysis of identically pretreated biomass. Four different modes of enzymatic hydrolysis and fermentation were trialed in the present study for optimization of the yield of ethanol. Two common yeasts viz., Saccharomyces cerevisiae and Pachysolen tannophilus, were used for fermentation of hexose and pentose sugars in the hydrolysate. Significant enhancement of concentration (8.3 g/L) and yield (0.21 g/g) of ethanol was obtained through a prefermentation hydrolysis-simultaneous saccharification and fermentation (PH-SSF) process, over the other three processes viz., separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), and single batch bioconversion (SBB) by utilizing fungal culture broth with and without filtration as crude enzyme source.