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Abstract
Background
Genetically customised Saccharomyces cerevisiae that can produce ethanol and additional bio-based chemicals from sustainable agro-industrial feedstocks (for example, residual plant biomass) are of major interest to the biofuel industry. We investigated the microbial biorefinery concept of ethanol and squalene co-production using S. cerevisiae (strain YUG37-ERG1) wherein ERG1 (squalene epoxidase) transcription is under the control of a doxycycline-repressible tet07-CYC1 promoter. The production of ethanol and squalene by YUG37-ERG1 grown using agriculturally sourced grass juice supplemented with doxycycline was assessed.
Results
Use of the tet07-CYC1 promoter permitted regulation of ERG1 expression and squalene accumulation in YUG37-ERG1, allowing us to circumvent the lethal growth phenotype seen when ERG1 is disrupted completely. In experiments using grass juice feedstock supplemented with 0 to 50 μg doxycycline mL−1, YUG37-ERG1 fermented ethanol (22.5 [±0.5] mg mL−1) and accumulated the highest squalene content (7.89 ± 0.25 mg g−1 dry biomass) and yield (18.0 ± 4.18 mg squalene L−1) with supplements of 5.0 and 0.025 μg doxycycline mL−1, respectively. Grass juice was found to be rich in water-soluble carbohydrates (61.1 [±3.6] mg sugars mL−1) and provided excellent feedstock for growth and fermentation studies using YUG37-ERG1.
Conclusion
Residual plant biomass components from crop production and rotation systems represent possible substrates for microbial fermentation of biofuels and bio-based compounds. This study is the first to utilise S. cerevisiae for the co-production of ethanol and squalene from grass juice. Our findings underscore the value of the biorefinery approach and demonstrate the potential to integrate microbial bioprocess engineering with existing agriculture.
Genetically customised Saccharomyces cerevisiae that can produce ethanol and additional bio-based chemicals from sustainable agro-industrial feedstocks (for example, residual plant biomass) are of major interest to the biofuel industry. We investigated the microbial biorefinery concept of ethanol and squalene co-production using S. cerevisiae (strain YUG37-ERG1) wherein ERG1 (squalene epoxidase) transcription is under the control of a doxycycline-repressible tet07-CYC1 promoter. The production of ethanol and squalene by YUG37-ERG1 grown using agriculturally sourced grass juice supplemented with doxycycline was assessed.
Results
Use of the tet07-CYC1 promoter permitted regulation of ERG1 expression and squalene accumulation in YUG37-ERG1, allowing us to circumvent the lethal growth phenotype seen when ERG1 is disrupted completely. In experiments using grass juice feedstock supplemented with 0 to 50 μg doxycycline mL−1, YUG37-ERG1 fermented ethanol (22.5 [±0.5] mg mL−1) and accumulated the highest squalene content (7.89 ± 0.25 mg g−1 dry biomass) and yield (18.0 ± 4.18 mg squalene L−1) with supplements of 5.0 and 0.025 μg doxycycline mL−1, respectively. Grass juice was found to be rich in water-soluble carbohydrates (61.1 [±3.6] mg sugars mL−1) and provided excellent feedstock for growth and fermentation studies using YUG37-ERG1.
Conclusion
Residual plant biomass components from crop production and rotation systems represent possible substrates for microbial fermentation of biofuels and bio-based compounds. This study is the first to utilise S. cerevisiae for the co-production of ethanol and squalene from grass juice. Our findings underscore the value of the biorefinery approach and demonstrate the potential to integrate microbial bioprocess engineering with existing agriculture.
Original language | English |
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Article number | 133 |
Number of pages | 9 |
Journal | Biotechnology for Biofuels |
Volume | 7 |
Early online date | 24 Sept 2014 |
DOIs | |
Publication status | Published - 2014 |
Keywords
- Bio-based products
- Squalene epoxidase
- Squalene
- Ethanol
- Sterol
- ERG1
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-
Iain Donnison
- Institute of Biological, Environmental & Rural Sciences (IBERS) - Professor, Head of Department - Biological Environmental and Rural Sciences
Person: Teaching And Research, Other
Projects
- 1 Finished
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Optimising energy output and biorefining
Donnison, I. (PI), Gallagher, J. (PI), Shah, I. P. (PI) & Winters, A. (PI)
Biotechnology and Biological Sciences Research Council
01 Apr 2012 → 31 Mar 2017
Project: Externally funded research