Co-production of ethanol and squalene using a Saccharomyces cerevisiae ERG1 (squalene epoxidase) mutant and agro-industrial feedstock

Biotechnology for Biofuels

Claire M Hull³  E Joel Loveridge¹  Nicola J Rolley³  Iain S Donnison²  Steven L Kelly³  Diane E Kelly³ 

[1] School of Chemistry, Cardiff University, Cardiff CF10 3AT, Wales, UK

[2] Institute of Biological, Environmental & Rural Sciences, Aberystwyth University, Gogerddan, Aberystwyth SY23 3EE, Wales, UK

[3] Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, Wales, UK

关键词: Squalene epoxidase;    Squalene;    Sterol;    Ethanol;    ERG1;    Bio-based products;   

Others  :  1084514
DOI  :  10.1186/s13068-014-0133-7

 received in 2014-01-29, accepted in 2014-08-29,  发布年份 2014

【 摘 要 】

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.

【 授权许可】

   
2014 Hull et al.; licensee BioMed Central Ltd.

【 图 表 】

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