Strain improvement of Sporolactobacillus inulinus ATCC 15538 for acid tolerance and production of D-lactic acid by genome shuffling.
Improvement of acid tolerance and production of D-lactic acid by Sporolactobacillus inulinus ATCC 15538 was performed by using recursive protoplast fusion in a genome shuffling format. The starting population was generated by ultraviolet irradiation, diethyl sulfate mutagenesis, and pH-gradient filter and then, subjected for the recursive protoplast fusion. The concentration of lysozyme, time, and temperature for enzyme treatment were optimized by response surface methodology based on the central composite design. Based on contour plots and variance analysis, the model predicted a maximum Y (multiply protoplasts formation ratio by protoplasts regeneration ratio), 60.4%, and the corresponding above used values were 7.75 mg/ml lysozyme, 1.59 h, and 38 degrees C. A pH-5-resistant recombinant, F3-4, was obtained after three rounds of genome shuffling and its production of D-lactic acid reached 93.4 g/l in a 5 L bioreactor, which was increased by 39.8% and 119% in comparison with that of UV generated strain and the original strain S. inulinus ATCC 15538, respectively. The subculture experiments indicated that F3-4 was genetically stable.
Department of Biochemical Engineering, School of Chemical Engineering and Technology, Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, Tianjin 300072, People's Republic of China.
Huijie
H
Zheng
Jixian
J
Gong
Tao
T
Chen
Xun
X
Chen
Xueming
X
Zhao
D056449:Bacillales / Q000235:genetics* / Q000378:metabolism*; D019149:Bioreactors; D001709:Biotechnology; D032621:DNA Shuffling; D004269:DNA, Bacterial / Q000235:genetics; D019020:Directed Molecular Evolution; D005285:Fermentation / Q000235:genetics; D014644:Genetic Variation; D016680:Genome, Bacterial; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology / Q000379:methods*; D019344:Lactic Acid / Q000096:biosynthesis; D016296:Mutagenesis; D011523:Protoplasts / Q000502:physiology; D013696:Temperature; D014466:Ultraviolet Rays
D004269:DNA, Bacterial; D019344:Lactic Acid; D005947:Glucose