Abstract: The original strain Bacillus licheniformis 2709 was mutagenized by means of nitrogen ion implantation at the optimal implantation dose of 1.5 × 1015 ions/cm2. As a result, a mutant strain  with a deamidation capacity of 48.99% (increased by 85.57% compared with the original strain) but a relatively weak ability to cleave peptide bonds named as SDL-9 was obtained. The orthogonal array design method was used for the optimization of fermentation conditions for production of alkaline protease with high deamidation capacity by SDL-9. The optimal fermentation conditions were 2 g/100 mL corn meal as the carbon source, 3 g/100 mL soybean protein as the nitrogen source, 0.04 g/100 mL Fe3+ with distinct promoting effect on enzyme production, 0.9 g/100 mL glutamine that could notably induce enzyme production, initial pH 7.0, and temperature 35 ℃. Under these conditions, the deamidation capacity and hydrolysis degree of peptide bonds were 57.1% and 13.2%, respectively.

Key words: nitrogen ion implantation, deamidation, alkaline protease