Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sources
Abstract Background Heterotrophic cultivation of microalgae has been proposed as a viable alternative method for novel high-value biomolecules, enriched biomass, and biofuel production because of their allowance of high cell density levels, as well as simple production technology. Tetradesmus bernar...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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BMC
2021-01-01
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| Series: | Biotechnology for Biofuels |
| Subjects: | |
| Online Access: | https://doi.org/10.1186/s13068-020-01868-9 |
| _version_ | 1811231476839088128 |
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| author | Baoyan Gao Feifei Wang Luodong Huang Hui Liu Yuming Zhong Chengwu Zhang |
| author_facet | Baoyan Gao Feifei Wang Luodong Huang Hui Liu Yuming Zhong Chengwu Zhang |
| author_sort | Baoyan Gao |
| collection | DOAJ |
| description | Abstract Background Heterotrophic cultivation of microalgae has been proposed as a viable alternative method for novel high-value biomolecules, enriched biomass, and biofuel production because of their allowance of high cell density levels, as well as simple production technology. Tetradesmus bernardii, a newly isolated high-yielding oleaginous microalga under photoautotrophic conditions, is able to grow heterotrophically, meaning that it can consume organic carbon sources in dark condition. We investigated the effect of different carbon/nitrogen (C/N) ratios on the growth and lipid accumulation of T. bernardii in heterotrophic batch culture under two nitrogen sources (NaNO3 and CO(NH2)2). In addition, we conducted time-resolved transcriptome analysis to reveal the metabolic mechanism of T. bernardii in heterotrophic culture. Results T. bernardii can accumulate high biomass concentrations in heterotrophic batch culture where the highest biomass of 46.09 g/L was achieved at 100 g/L glucose concentration. The rate of glucose to biomass exceeded 55% when the glucose concentration was less than 80 g/L, and the C/N ratio was 44 at urea treatment. The culture was beneficial to lipid accumulation at a C/N ratio between 110 and 130. NaNO3 used as a nitrogen source enhanced the lipid content more than urea, and the highest lipid content was 45% of dry weight. We performed RNA-seq to analyze the time-resolved transcriptome of T. bernardii. As the nitrogen was consumed in the medium, nitrogen metabolism-related genes were significantly up-regulated to speed up the N metabolic cycle. As chloroplasts were destroyed in the dark, the metabolism of cells was transferred from chloroplasts to cytoplasm. However, storage of carbohydrate in chloroplast remained active, mainly the synthesis of starch, and the precursor of starch synthesis in heterotrophic culture may largely come from the absorption of organic carbon source (glucose). With regard to lipid metabolism, the related genes of fatty acid synthesis in low nitrogen concentration increased gradually with the extension of cultivation time. Conclusion T. bernardii exhibited rapid growth and high lipid accumulation in heterotrophic culture. It may be a potential candidate for biomass and biofuel production. Transcriptome analysis showed that multilevel regulation ensured the conversion from carbon to the synthesis of carbohydrate and lipid. |
| first_indexed | 2024-04-12T10:45:55Z |
| format | Article |
| id | doaj.art-af428c1d4b96445a850232648bb686a8 |
| institution | Directory Open Access Journal |
| issn | 1754-6834 |
| language | English |
| last_indexed | 2024-04-12T10:45:55Z |
| publishDate | 2021-01-01 |
| publisher | BMC |
| record_format | Article |
| series | Biotechnology for Biofuels |
| spelling | doaj.art-af428c1d4b96445a850232648bb686a82022-12-22T03:36:26ZengBMCBiotechnology for Biofuels1754-68342021-01-0114111610.1186/s13068-020-01868-9Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sourcesBaoyan Gao0Feifei Wang1Luodong Huang2Hui Liu3Yuming Zhong4Chengwu Zhang5Department of Ecology, Research Center for Hydrobiology, Jinan UniversityDepartment of Ecology, Research Center for Hydrobiology, Jinan UniversityDepartment of Ecology, Research Center for Hydrobiology, Jinan UniversityCollege of Resources and Environment, Zhongkai University of Agriculture and EngineeringCollege of Resources and Environment, Zhongkai University of Agriculture and EngineeringDepartment of Ecology, Research Center for Hydrobiology, Jinan UniversityAbstract Background Heterotrophic cultivation of microalgae has been proposed as a viable alternative method for novel high-value biomolecules, enriched biomass, and biofuel production because of their allowance of high cell density levels, as well as simple production technology. Tetradesmus bernardii, a newly isolated high-yielding oleaginous microalga under photoautotrophic conditions, is able to grow heterotrophically, meaning that it can consume organic carbon sources in dark condition. We investigated the effect of different carbon/nitrogen (C/N) ratios on the growth and lipid accumulation of T. bernardii in heterotrophic batch culture under two nitrogen sources (NaNO3 and CO(NH2)2). In addition, we conducted time-resolved transcriptome analysis to reveal the metabolic mechanism of T. bernardii in heterotrophic culture. Results T. bernardii can accumulate high biomass concentrations in heterotrophic batch culture where the highest biomass of 46.09 g/L was achieved at 100 g/L glucose concentration. The rate of glucose to biomass exceeded 55% when the glucose concentration was less than 80 g/L, and the C/N ratio was 44 at urea treatment. The culture was beneficial to lipid accumulation at a C/N ratio between 110 and 130. NaNO3 used as a nitrogen source enhanced the lipid content more than urea, and the highest lipid content was 45% of dry weight. We performed RNA-seq to analyze the time-resolved transcriptome of T. bernardii. As the nitrogen was consumed in the medium, nitrogen metabolism-related genes were significantly up-regulated to speed up the N metabolic cycle. As chloroplasts were destroyed in the dark, the metabolism of cells was transferred from chloroplasts to cytoplasm. However, storage of carbohydrate in chloroplast remained active, mainly the synthesis of starch, and the precursor of starch synthesis in heterotrophic culture may largely come from the absorption of organic carbon source (glucose). With regard to lipid metabolism, the related genes of fatty acid synthesis in low nitrogen concentration increased gradually with the extension of cultivation time. Conclusion T. bernardii exhibited rapid growth and high lipid accumulation in heterotrophic culture. It may be a potential candidate for biomass and biofuel production. Transcriptome analysis showed that multilevel regulation ensured the conversion from carbon to the synthesis of carbohydrate and lipid.https://doi.org/10.1186/s13068-020-01868-9Tetradesmus bernardiiHeterotrophyOleaginous microalgaeC/N ratioTranscriptome |
| spellingShingle | Baoyan Gao Feifei Wang Luodong Huang Hui Liu Yuming Zhong Chengwu Zhang Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sources Biotechnology for Biofuels Tetradesmus bernardii Heterotrophy Oleaginous microalgae C/N ratio Transcriptome |
| title | Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sources |
| title_full | Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sources |
| title_fullStr | Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sources |
| title_full_unstemmed | Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sources |
| title_short | Biomass, lipid accumulation kinetics, and the transcriptome of heterotrophic oleaginous microalga Tetradesmus bernardii under different carbon and nitrogen sources |
| title_sort | biomass lipid accumulation kinetics and the transcriptome of heterotrophic oleaginous microalga tetradesmus bernardii under different carbon and nitrogen sources |
| topic | Tetradesmus bernardii Heterotrophy Oleaginous microalgae C/N ratio Transcriptome |
| url | https://doi.org/10.1186/s13068-020-01868-9 |
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