Methods of utilizing reduced cellulase loads to hydrolyze cellulosic substrates are disclosed. The methods include determining an amount of purified cellulase necessary to substantially hydrolyze a quantity of cellulosic substrate in a period of time; reducing the amount of purified cellulase by a factor of between 2 and 5 to determine a reduced cellulase load; and introducing to the cellulosic substrate either (1 ) a microorganism expressing cell-bound cellulase in a concentration equal to the reduced cellulase load or (2) a fermentation agent that has been engineered to express cell-bound cellulase in a concentration equal to the reduced cellulase load under suitable conditions and for said period of time sufficient to allow substantial hydrolysis of the cellulosic substrate.
