Low-energy N ~ + Injected L-the Ile Produce Bacteria Breeding And Fermentation Conditions

Used as the mutagen, the low energy ion beam showed many good effects including high mutagenic ratio, extensively mutagenic spectrum and low damage ratio in microorganism mutagenic breeding.The L-isoleucine producer Corynebacterium crematum AS 1.998 was mutated by low energy N⁺ ion beam implanting and UV ,the plate screening with amino acid analogues :ethiomine (Eth) for screening high yielding strain in this study.The strain N24, one of mutants was showed preference to produce L-isoleucine. The L-isoleucine yield of N24 was 0.642g/100ml and was more 43.95% than that of AS 1.998. The genetic stability of strain N24 is comparative stable.The flask shaking fermention culture medium of N24 was discussed ,using single factor analysis method and orthogonality experiment. The results showed that the optimal seed medium were glucose 7%, Corn steep liquor 1.8%, peptone 0.5%, KH₂PO₄ 0.1%, MgSO₄ 0.05% and urea 0.4%. The optimal fermention medium were glucose 12%, (NH₄)₂SO₄6%, K₂HPO₄0.06%, Corn steep liquor 1.0% and acid-liquid of wheat bran 1.0%. Using these optimal medium,the yield of L-isoleucine was 0.744 g/100ml and was more 15.89% than that cultured by original mediums.In this study, the flask shaking fermention techniques conditions of N24 were optimized. The result showed that the optimal fermention culture conditions were the original pH 7.2 ,entering CaCO₃ for modulating pH, inoculum size 10%, volume of shake flask 25ml/500ml, shake speed 200rpm and culture temperature 28℃.After a 72-hour fermentation,the final L-isoleucine concentration was 0.744 g/100ml.Using these optimal medium, the L-isoleucine yield of N24 was 0.775g/100ml and was more 73.77% than 0.446g/100ml of AS 1.998. The genetic stability of strain N24 is comparative stable.