A wide scale of monosaccharide or disaccharide or other sugar-based oligomeric or poly­meric substrates can be used as starting material in ABE fermentations. Compere and Griffith [20] studied the effect of substrate types on the yield and distribution of valua­ble ABE products with different strains of Clostridia. Different concentrations (2.5-10%) of arabinose, ribose, xylose, xylane, fructose, glucose, cellobiose, lactose, sucrose, dextrin and cellulose were tested and the amount and the distribution of acetone, ethanol, buta­nol and the H2/CO2 ratio strongly depended on the type of strain, the type of sugar and their concentrations as well. Ounine et al. [21] studied the fermentation of glucose, arabi­nose and xylose with C. Acetobutylicum and found conversion into solvents in 32, 29, and 28%, respectively. Growth yields were similar on the all sugars, but glucose or arabi­nose was consumed in preference to xylose and with faster growth. It means that not on­ly corn, cereals, molasses, but wastes of dairy products [22,23] or agricultural byproducts as corn stalk, corncob, cellulose wastes and other raw materials can also be utilized [24,25]. By using wastes, however, it is an important key factor that the contaminants can prevent the ABE fermentation. For example, when alkaline peroxide pretreated wheat straw was hydrolyzed using cellulolytic and xylanolytic enzymes, and the hydro — lyzate was used to produce butanol using Clostridium beijerinckii P260, the culture pro­duced less than 2.59 g L-1 ABE solvents, but after removal of the formed inhibitor salts with electrodialysis, 22.17 g/L of ABE solvents were formed. This was higher value than the ABE solvent concentration (21.37 g/L) given from glucose. A comparison of use of different substrates (corn fiber, wheat straw) and different pretreatment techniques (di­lute sulfuric acid, alkaline peroxide) suggested that generation of inhibitors was substrate and pretreatment specific [26]. Selection of raw material for ABE process cannot be inde­pendent from the selection of the bacteria strain. For example, cassava, due to its high starch content and low cost, is a promising candidate substrate for large-scale ABE fer­mentation processes. However, the solvent yield from the fermentation of cassava reach­es only 60% of that achieved by fermenting corn. Addition of ammonium acetate (CH^COONHJ to the cassava medium significantly promotes solvent production with a high butanol ratio C. Acetobutylicum mutant (EA 2018). When cassava medium was sup­plemented with 30 mM ammonium acetate, the acetone, butanol and total solvent prodn. reached 5.0, 13.0 and 19.4 g/l, respectively, after 48 h of fermentation which level of sol­vent production is comparable to that obtained from corn medium. Both ammonium (NH4+) and acetate (CH3COO-) were required for increased solvent synthesis [27]