Heterotrophic growth of Neochloris oleoabundans using glucose as a carbon source

Biotechnology for Biofuels

Daniela Morales-Sánchez²  Raunel Tinoco-Valencia²  John Kyndt¹  Alfredo Martinez² 

[1] College of Science and Technology, Bellevue University, 1000 Galvin Road South, Bellevue, NE, 68005, USA

[2] Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, A P 510-3, Cuernavaca, Morelos, 62250, México

关键词: Protein;    Lipids;    Nitrate;    Fed-batch;    Glucose transporter;    Glucose;    Heterotrophic growth;    Neochloris oleoabundans;   

Others  :  797987
DOI  :  10.1186/1754-6834-6-100

 received in 2012-12-19, accepted in 2013-07-08,  发布年份 2013

【 摘 要 】

Background

In comparison with phototrophic growth, heterotrophic conditions can significantly increase growth rates, final cell number and cell mass in microalgae cultures. Neochloris oleoabundans is a microalga of biotechnological interest that accumulates lipids under phototrophic and nitrogen-limited conditions. Heterotrophic flask culture experiments were conducted to identify carbon sources that can be metabolized by N. oleoabundans, and bioreactor batch and fed-batch (nitrate pulse additions) cultures supplemented with glucose were performed to study the cellular composition of the microalgae under balanced and high C/N ratios (glucose/nitrate).

Results

N. oleoabundans was able to grow using glucose and cellobiose as sole carbon sources under strict heterotrophic conditions. Under a balanced C/N ratio of 17 and using bioreactor batch cultures containing 3 g/L glucose, a maximal cell mass of 1.72 g/L was found, with protein being the major cell component (44% w/w). A maximal cell mass of 9.2 g/L was obtained using batch cultures at a C/N ratio of 278. Under these conditions, lipid accumulation was promoted (up to 52% w/w) through N-limitation, resulting in high lipid productivity (528.5 mg/L/day). Fed-batch cultures were performed at a C/N ratio of 278 and with nitrate pulse additions. This condition allowed a maximal cell mass of 14.2 g/L to be achieved and switched the metabolism to carbohydrate synthesis (up to 54% of dry weight), mainly in the form of starch. It was found that transmembrane transport under these conditions was dependent on a proton-motive force, indicating that glucose is transported by a symporter.

Conclusions

N. oleoabundans was able to grow under strict heterotrophic culture conditions with glucose or cellobiose as the only carbon source. The glucose used is transported by a symporter system. Batch cultures with a balanced C/N ratio accumulate proteins as the major cellular component; a high C/N ratio significantly increased the dry cell mass and resulted in a high lipid content, and a high cell density was achieved using fed-batch cultures promoting carbohydrate accumulation. These results suggest heterotrophic batch cultures of N. oleoabundans as an alternative for the production of proteins or lipids with simple culture strategies and minimal-mineral media supplemented with glucose.

【 授权许可】

   
2013 Morales-Sánchez et al.; licensee BioMed Central Ltd.

【 图 表 】

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