Abstract: Bacillus cereus BC-0801, a β-cyclodextrin glycosyltransferase (β-CGTase)-producing strain, was mutagenized by means of low energy (10 keV) N+ ion implantation at a dose of 40 × 2.5 × 1013 ions/cm2 to obtain a high-yield mutant strain designated as BC-0802. The effects of carbon and nitrogen sources and inorganic salt (K2HPO4) in the medium on β-CGTase production by BC-0802 were investigated by one-factor-at-a-time method. The three components were optimized by orthogonal array design method. The optimal fermentation medium was composed of corn flour 30 g/L, yeast extract 15 g/L, K2HPO4 1 g/L. The optimal fermentation conditions were determined as inoculum size 2%, fermentation period 36 h, temperature 30 ℃, and pH 9.0. The average β-CGTase activity of the mutant strain was 3415.8 U/mL (n = 5), which was 3.67 times higher than that of the starting strain. Moreover the mutant strain showed good genetic stability.

Key words: N+ ion implantation, β-cyclodextrin glycosyltransferase, screening, mutagenesis, technological optimization