Sugar beet is considered the second source of sugar production in the world, but it becomes the first source in Egypt and several other countries all over the world. The present study aimed to convert the agro-industrial beet pulp that consists of cellulosic material into fermentable sugars as a friendly source of energy. The cellulases producing bacteria and actinomycetes are associated with beets' pulps and roots. The study also aimed to optimize the conditions of cellulases production, e.g., incubation time, temperature and pH. One hundred and two isolates of bacteria and actinomycetes were isolated from these samples and then screened to determine their potency to produce cellulases. Seven isolates were recorded as high producers (two from rhizospheres, one from endophytes, and four from the beet pulp). These seven isolates were classified according to morphological and biochemical tests as S11 (Streptomyces), S31 (Streptomyces), S45 (Bacillus), and S72 (Bacillus), S73 (Streptomyces), S85 (Streptococcus) and S88 (Bacillus). Optimization for the incubation period, temperature, and pH showed that activities of the highest three tested isolates S11, S45, and S88 were 0.73, 0.17, and 0.54 U/ml after two days of the incubation period. These levels increased to 1.33, 0.24 and 0.76 U/ml on the fourth incubation day at different temperatures and pH degrees. According to the results, it is recommended to use bacteria (Streptomyces), which is sample No. S11 isolated from the rhizosphere soil of beetroots was the high producer of cellulases at 50°C and pH 7.