TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Method: In the method of potentiating enzymatic saccharification of a cellulosic biomass using a microbial enzyme cocktail, the microbial enzyme cocktail is provided at a sub-maximum dose. The cellulase enzyme is selected from cellobiohydrolase I, cellobiohydrolase II and endoglucanase. The microbial enzyme cocktail is an enzyme cocktail from Trichoderma reesei, Trichoderma longibrachiatum, or Saccharophagus degradans. The cellulase enzyme is provided by its expression by a transgenic plant comprising a heterologous nucleic acid encoding the same, where the transgenic plant is selected from sorghum, maize, soybean, switchgrass and sugar cane. The biomass comprises the transgenic plant. The cellulosic biomass comprises sugarcane bagasse, corn seed fiber, corn stover, switchgrass, wood pulp, or straw of rice, wheat or barley. The cellulosic biomass is pretreated. Producing fermentable sugars, comprises combining a cellulosic biomass with a composition comprising a microbial enzyme cocktail and at least one cellulase enzyme under conditions conducive to producing fermentable sugars, to thus produce fermentable sugars. The method further comprises fermenting the fermentable sugars to produce ethanol. Producing fermentable sugars, comprises (a) providing a mixture of (i) a transgenic plant comprising a cellulase enzyme expressed from a heterologous nucleic acid encoding the same in it, and (ii) a composition comprising a microbial enzyme cocktail, and (b) providing conditions conducive to producing fermentable sugars from the mixture, to thus produce the fermentable sugars. The transgenic plant expresses 1-30 mg of the cellulase enzyme per gram of cellulose of the plant. The cellulase enzyme is selected from cellobiohydrolase I, cellobiohydrolase II and endoglucanase, where the cellobiohydrolase I, cellobiohydrolase II or endoglucanase comprises a heterologous linker sequence. The microbial enzyme cocktail is provided at a concentration of 5-90 mg/gram of cellulose of the plant, preferably 10-50 mg/gram of cellulose of the plant. EXAMPLE - No suitable example given.