Enhanced production of l‐lactic acid by Lactobacillus thermophilus SRZ50 mutant generated by high‐linear energy transfer heavy ion mutagenesis |
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Authors: | Ai‐lian Jiang Wei Hu Wen‐jian Li Lu Liu Xue‐jiao Tian Jing Liu Shu‐yang Wang Dong Lu Ji‐hong Chen |
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Affiliation: | 1. Department of Biophysics, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, P. R. China;2. University of Chinese Academy of Sciences, Beijing, P. R. China |
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Abstract: | The aim of this study was to improve l ‐lactic acid production of Lactobacillus thermophilus SRZ50. For this purpose, high efficient heavy‐ion mutagenesis technique was performed using SRZ50 as the original strain. To enhance the screening efficiency for high yield l ‐lactic acid producers, a scale‐down from shake flask to microtiter plate was developed. The results showed that 24‐well U‐bottom MTPs could well alternate shake flasks for L. thermophilus cultivation as a scale‐down tool due to its a very good comparability to the shake flasks. Based on this microtiter plate screening method, two high l ‐lactic acid productivity mutants, A59 and A69, were successfully screened out, which presented, respectively, 15.8 and 16.2% higher productivities than that of the original strain. Based on fed‐batch fermentation, the A69 mutant can accumulate 114.2 g/L l ‐lactic acid at 96 h. Hence, the proposed traditional microbial breeding method with efficient high‐throughput screening assay was proved to be an appropriate strategy to obtain lactic acid‐overproducing strain. |
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Keywords: | Heavy ion mutagenesis High productivity High‐throughput screening Lactobacillus thermophilus l‐lactic acid |
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