In this study, the pullulanase gene from Bacillus deramificans was efficiently expressed in Brevibacillus choshinensis. The optimal medium for protein expression was determined through a combination of single-factor experiments and response surface methodology. The initial pH of the medium and the culture temperature were optimized. The pullulanase yield increased 10.8-fold through medium and condition optimization at the shake-flask level. From the results of these experiments, the dissolved oxygen level was optimized in a 3-L fermentor. Under these optimized conditions, the pullulanase activity and the specific pullulanase productivity reached 1005.8 U/mL and 110.5 × 10(3) U/g dry cell weight, respectively, with negligible intracellular expression. The Brevibacillus choshinensis expression system has proven to be valuable for the extracellular production of pullulanase.
Keywords: Bacillus deramificans; Brevibacillus choshinensis; Fermentation optimization; Pullulanase; Response surface methodology.