Optimization and purification of mannanase produced by an alkaliphilic-thermotolerant Bacillus cereus N1 isolated from Bani Salama Lake in Wadi El-Natron

An alkaliphilic-thermotolerant Bacillus cereus N1 isolated from Bani Salama Lake, Wadi El-Natron, Egypt, was proved to produce mannanase enzyme. Optimization of the fermentation medium components using Plackett-Burman design was applied. Glucose and inoculum size were found to be the most significant factors enhancing the production of the enzyme. On applying optimized medium in the fermentation process, an enzyme productivity of 42.2 UmL-1 was achieved with 6.4 fold increase compared to the basal one. Mannanase was also extracted and purified using chromatography such as ion-exchange chromatographic and gel filtration methods. It was indicated that, the mannanase activity extracted and purified from the isolate B. cereus N1 was reduced to 321.6 U (about 36% of the whole mannanase in the culture filtrate) in comparison with the initial mannanase activity (900 U) and the total protein content reduced to 52 mg (the initial total protein content was 220 mg). However, the specific activity for the mannanase from B. cereus N1 at the end of the purification steps was found to be about 628 Umg-1 compared to 4.2 Umg-1 at the initial culture filtrate. It was also indicated that the mannanase enzyme was purified almost 149-fold.