A reliable production of heterologous proteins is important in the field of industrial biotechnology. This can be achieved by applying auto-inducible gene expression systems. Development of a Bacillus subtilis expression plasmid harboring SigB-dependent ohrB promoter was reported. The expression system was subjected to high cell density cultivation to produce xylanase as a stable model protein. The recombinant strain was cultured in a synthetic medium containing glucose as the carbon source. The exponential fed-batch feeding strategy was applied to prevent substrate inhibition. A sharp increase of xylanase activity (about 6-fold) at the end of fermentation was observed as a result of sigma factor B (SigB) protein activation, supporting auto-inducibility of the expression system. For the control strain a specific induction of the xylanase activity was not observed. The recombinant strain showed a 5-fold increase in xylanase activity in comparison with the control strain. In addition, the constructed system displayed the catabolite repression resistance ability. This SigB-dependent expression system can be considered as a biotechnological tool and an alternative to the high costing conventional inducers, e.g. isopropyl-β-galactopyranoside.