Bacillus cereus V9 is a mannanolytic bacteria capable of producing a mannanase enzyme of 29.5 IU / mL with a substrate of Locust bean gun. The use of Locust bean gum as a substrate in the production of the enzyme mannanase is not recommended because it is expensive so that the enzyme produced will be expensive. The use of local mannan substrates such as porang, coconut pulp, coconut cake, and palm kernel meal has the opportunity to replace Locust bean gum because the mannan content is almost equal to the content of the mannan Locust bean gum so the resulting enzyme is cheaper. This study aims to determine the best local mannan biomass substrate as a substitute for Locust bean gum for the production of the mannanase enzyme from Bacillus cereus V9 bacteria. This study consisted of two stages where the first stage was the optimization of the production of mannanase enzymes in various alternative substrates for Locust bean gum, then the second stage was the production of the enzyme mannanase from the selected substrate as a substitute for Locust bean gum. Simple data analysis is based on calculating the number and average of each observation from 4 replications and the data is displayed in the form of a descriptive narrative. The results showed that Bacillus cereus V9 could grow on all local mannan media and the highest was on palm kernel meal media. The growth of Bacillus cereus V9 at a substrate concentration of 1% palm kernel meal did not differ from a concentration of 1.5% and 2%. The activity of the mannanase enzyme Bacillus cereus V9 in palm kernel meal media was higher when compared to porang, coconut cake, and coconut pulp. This study concludes that palm kernel meal can be used as a 1% substrate as a substitute for Locust bean gum in the production of the enzyme mannanase from Bacillus cereus V9.