Study on mutation and screening of Actinobacillus succinogens mutant and its fermentation control

• Main Authors: CHUANG,MENG-SHIN, 莊孟歆
• Other Authors: LEE,WEN-CHIEN
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/15722220793385488841

碩士 === 國立中正大學 === 化學工程研究所 === 104 === Actinobacillus succinogens (BCRC 80310) was used by the starting strain in this study. The present work studied the influence of pH control on the fermentation of A. succinogens use glycerol as the carbon source. During the bacterial fed-batch fermentation, the pH value was adjusted at 6.8 using 5 N NaOH or a combined liquor of 4 N NaOH and 4 N Mg(OH)2. Results suggest that higher sodium concentration in the fermentation medium because pH titration with higher concentration NaOH could significantly inhibit the cell growth and consequently reduce the production of succinic acid. After N-methyl-N′-nitro-N-nitrosoguanidine (NTG) treatment to induce bacterial mutation, a mutant strain (mu-b7) of A. succinogens was obtained. In the batch fermentation, the pH controlling strategy using combined liquor to adjust pH at 6.7 which was able to solve the problem of Na+ accumulation. Moreover concentration of succinic acid could reach 44.57 g/L, with a production rate of 0.75 g/L/hr and a succinic acid to acetic ratio of 12.3. The succinic acid yield was 1.09 g/g. In the batch fermentation of mutant strain with higher concentration of glycerol, the lag phase time was longer than that of wild type. This problem could be solved by the adaptation of mutant bacterial cells in glycerol in pre-culture stage. Furthermore, the concentration of succinic acid could reach 44.77 g/L, with a production rate of 0.9 g/L/hr and a succinic acid to acetic ratio of 14.3. The succinic acid yield was 1.12 g/g. In addition to adding glycerol in pre-culture, the fed-batch fermentation was also used to reduce the inhibition of glycerol. Finally, the concentration of succinic acid could each 61.61 g/L, with a production rate of 1.2 g/L/hr and the succinic acid to acetic ratio of 12.6. The succinic acid yield was 1.07 g/g.