Orange waste coming from food industries is used in continuous fermenta­tion. It has been found that fixed bed immobilized cell reactor showed maximum ethanol production [50]. Use of citrus processing by-product mainly peel by fermentation by S. cerevisiae for ethanol production has been reported [58, 94]. The initial saccharification of polysaccharides by commercial cellulase and poly­galacturonase followed by removal of inhibitory compounds by filtration and pH adjustment of the hydrolysate was necessary for successful fermentation [29].

Ethanol has also been produced from lignocellulosic waste by employing recombinant bacterial strains of E. coli and Klebsiella oxytoca [91]. The bacterial strains had the capacity to produce ethanol from pentose sugars. The conversion of monosaccharides in orange peel hydrolysates into ethanol by recombinant E. coli (KOll) was in pH controlled batch fermentations that led to very high yields of ethanol. The microorganism was capable of converting all major monosaccharides in orange peel hydrolysates into ethanol and to a smaller amount of acetic and lactic acids [57]. Citrus molasses prepared by evaporation and concentration of the press liquor and molasses mixed with the citrus pulp have also been used by distillaries as an alcohol feedstock [50]. Initial moisture content of the solid medium has been shown to be a limiting factor for maximum ethanol production [130]. Industrial alcohol has also been produced from waste fruits such as apple, pear, and cherry through fermentation [11].