Improvement of a fed-batch process for high level xylanase production by a Bacillus strain

International audienceIn this paper, the improvement of a fed-batch fermentation from the point of view of an industrial xylanase production process is described. The Bacillus strain chosen for this study is able to produce high quantities of a xylanase that is suitable to be used as bleach boost agent in chlorine-free bleaching sequences of paper pulp. It was found that xylo-oligosaccharides hydrolysis products from xylan by xylanase action were indispensable for induction of the enzyme synthesis, but that their presence in quantities of only 0.1g dm^-3 xylose equivalents led to catabolite repression. A substrate-limited fed-batch process, that is the most adapted, was furthermore improved with regard to nutrient requirement of the microorganism, especially the nitrogen source. A process with constant supply of a culture medium containing xylan, peptone and mineral nitrogen was able to produce 20240nkatcm^-3 with a productivity of 910nkatcm^-3 h^-1, which places the process among the best ever reported