The cellulose fraction of lignocelluloses can be converted to ethanol by either simultaneous saccharification and fermentation (SSF) or separate enzymatic hydrolysis and fermentation (SHF) processes. A schematic of these processes is shown in Fig. 3.9. It is also possible to combine the cellulase production, enzymatic hydrolysis, and fermentation in one step, called direct microbial conversion (DMC). There are cost savings because of the reduced number of required vessels. However, there is less attention to DMC for industrial purposes because of the low ethanol yield in DMC, formation of several by-products, and low ethanol toler­ance of the microorganisms used [2].