Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strain
Abstract Background Optically pure d-lactic acid (≥ 99%) is an important precursor of polylactic acid. However, there are relatively few studies on d-lactic acid fermentation compared with the extensive investigation of l-lactic acid production. Most lactic acid producers are mesophilic organisms. O...
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| Format: | Article |
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BMC
2017-11-01
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| Series: | Microbial Cell Factories |
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| Online Access: | http://link.springer.com/article/10.1186/s12934-017-0827-1 |
| _version_ | 1818990421450162176 |
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| author | Caili Zhang Cheng Zhou Nilnate Assavasirijinda Bo Yu Limin Wang Yanhe Ma |
| author_facet | Caili Zhang Cheng Zhou Nilnate Assavasirijinda Bo Yu Limin Wang Yanhe Ma |
| author_sort | Caili Zhang |
| collection | DOAJ |
| description | Abstract Background Optically pure d-lactic acid (≥ 99%) is an important precursor of polylactic acid. However, there are relatively few studies on d-lactic acid fermentation compared with the extensive investigation of l-lactic acid production. Most lactic acid producers are mesophilic organisms. Optically pure d-lactic acid produced at high temperature not only could reduce the costs of sterilization but also could inhibit the growth of other bacteria, such as l-lactic acid producers. Results Thermophilic Bacillus coagulans is an excellent producer of l-lactic acid with capable of growing at 50 °C. In our previous study, the roles of two l-lactic acid dehydrogenases have been demonstrated in B. coagulans DSM1. In this study, the function of another annotated possible l-lactate dehydrogenase gene (ldhL3) was verified to be leucine dehydrogenase with an activity of 0.16 units (μmol/min) per mg protein. Furthermore, the activity of native d-lactate dehydrogenase was too low to support efficient d-lactic acid production, even under the control of strong promoter. Finally, an engineered B. coagulans D-DSM1 strain with the capacity for efficient production of d-lactic acid was constructed by deletion of two l-lactate dehydrogenases genes (ldhL1 and ldhL2) and insertion of the d-lactate dehydrogenase gene (LdldhD) from Lactobacillus delbrueckii subsp. bulgaricus DSM 20081 at the position of ldhL1. Conclusions This genetically engineered strain produced only d-lactic acid under non-sterilized condition, and finally 145 g/L of d-lactic acid was produced with an optical purity of 99.9% and a high yield of 0.98 g/g. This is the highest optically pure d-lactic acid titer produced by a thermophilic strain. |
| first_indexed | 2024-12-20T19:54:06Z |
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| id | doaj.art-a2b172fc0ffd4998a9708dad346f488c |
| institution | Directory Open Access Journal |
| issn | 1475-2859 |
| language | English |
| last_indexed | 2024-12-20T19:54:06Z |
| publishDate | 2017-11-01 |
| publisher | BMC |
| record_format | Article |
| series | Microbial Cell Factories |
| spelling | doaj.art-a2b172fc0ffd4998a9708dad346f488c2022-12-21T19:28:13ZengBMCMicrobial Cell Factories1475-28592017-11-0116111010.1186/s12934-017-0827-1Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strainCaili Zhang0Cheng Zhou1Nilnate Assavasirijinda2Bo Yu3Limin Wang4Yanhe Ma5CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of SciencesState Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of SciencesDepartment of Biology, Faculty of Science, King Mongkut’s Institute of Technology LadkrabangCAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of SciencesCAS Key Laboratory of Microbial Physiological and Metabolic Engineering, Institute of Microbiology, Chinese Academy of SciencesState Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of SciencesAbstract Background Optically pure d-lactic acid (≥ 99%) is an important precursor of polylactic acid. However, there are relatively few studies on d-lactic acid fermentation compared with the extensive investigation of l-lactic acid production. Most lactic acid producers are mesophilic organisms. Optically pure d-lactic acid produced at high temperature not only could reduce the costs of sterilization but also could inhibit the growth of other bacteria, such as l-lactic acid producers. Results Thermophilic Bacillus coagulans is an excellent producer of l-lactic acid with capable of growing at 50 °C. In our previous study, the roles of two l-lactic acid dehydrogenases have been demonstrated in B. coagulans DSM1. In this study, the function of another annotated possible l-lactate dehydrogenase gene (ldhL3) was verified to be leucine dehydrogenase with an activity of 0.16 units (μmol/min) per mg protein. Furthermore, the activity of native d-lactate dehydrogenase was too low to support efficient d-lactic acid production, even under the control of strong promoter. Finally, an engineered B. coagulans D-DSM1 strain with the capacity for efficient production of d-lactic acid was constructed by deletion of two l-lactate dehydrogenases genes (ldhL1 and ldhL2) and insertion of the d-lactate dehydrogenase gene (LdldhD) from Lactobacillus delbrueckii subsp. bulgaricus DSM 20081 at the position of ldhL1. Conclusions This genetically engineered strain produced only d-lactic acid under non-sterilized condition, and finally 145 g/L of d-lactic acid was produced with an optical purity of 99.9% and a high yield of 0.98 g/g. This is the highest optically pure d-lactic acid titer produced by a thermophilic strain.http://link.springer.com/article/10.1186/s12934-017-0827-1Bacillus coagulansGenetic engineeringd-Lactic acidOptically pureNon-sterilized fermentation |
| spellingShingle | Caili Zhang Cheng Zhou Nilnate Assavasirijinda Bo Yu Limin Wang Yanhe Ma Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strain Microbial Cell Factories Bacillus coagulans Genetic engineering d-Lactic acid Optically pure Non-sterilized fermentation |
| title | Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strain |
| title_full | Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strain |
| title_fullStr | Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strain |
| title_full_unstemmed | Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strain |
| title_short | Non-sterilized fermentation of high optically pure d-lactic acid by a genetically modified thermophilic Bacillus coagulans strain |
| title_sort | non sterilized fermentation of high optically pure d lactic acid by a genetically modified thermophilic bacillus coagulans strain |
| topic | Bacillus coagulans Genetic engineering d-Lactic acid Optically pure Non-sterilized fermentation |
| url | http://link.springer.com/article/10.1186/s12934-017-0827-1 |
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