ABSTRACT
A strain Actinobacillus succinogenes CGMCC 1593 was selected as the parent strain.After UV-EMS and UV-DES treatments respectively,seven mutated strains with subtle improvements in acid tol-erance were obtained,and were subjected for recursive protoplast fusion.Through three rounds of genome shuffling,four shuffled strains with both higher yield and acid tolerance were obtained.The shuffled strain namely F3-21 could even survive at pH 5.2.The comparison of the shuffled strains and the parent strain for succinic acid production was also studied here.After 48 h of shake-flask fermentation,the succinic acid concentration of F3-21 was 48% higher than that of the parent strain.When F3-21 was carried out in a 5 liter stirred bioreactor with pH controlled 5.6~6.0,the accumulation of succinic acid in 48 h fermentation attained 38.1 g/L,which was increased by 45% compared with that of the parent strain(26.2 g/L).While pH was controlled at 6.5~7.0,the production of succinic acid in 32 h fermentation attained 40.7 g/L.When F3-21 was carried out in fed-batch fermentation,succinic acid concentration of 67.4 g/L was reached in 72 h fer-mentation.These results indicated that the genome shuffling could improve the acid tolerance and the suc-cinic acid production of A.succinogenes CGMCC 1593.