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Low-cost lipid production by an oleaginous yeast cultured in non-sterile conditions using model waste resources.

Santamauro F, Whiffin FM, Scott RJ, Chuck CJ - Biotechnol Biofuels (2014)

Bottom Line: This approach resulted in yields of up to 40% lipid, which compares favourably with other oleaginous microbes.We also demonstrate that M. pulcherrima metabolises glycerol and a diverse range of other sugars, suggesting that heterogeneous biomass could provide a suitable carbon source.M. pulcherrima also grows well in a minimal media containing no yeast extract.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK. R.J.Scott@bath.ac.uk.

ABSTRACT

Background: The yeast Metschnikowia pulcherrima, previously utilised as a biological control agent, was evaluated for its potential to produce lipids for biofuel production.

Results: Cultivation in low cost non-sterile conditions was achieved by exploiting its ability to grow at low temperature and pH and to produce natural antimicrobial compounds. Although not previously classified as oleaginous, a combination of low temperature and restricted nutrient availability triggered high levels of oil production in M. pulcherrima cultures. This regime was designed to trigger the sporulation process but prevent its completion to allow the accumulation of a subset of a normally transitional, but oil-rich, 'pulcherrima' cell type. This approach resulted in yields of up to 40% lipid, which compares favourably with other oleaginous microbes. We also demonstrate that M. pulcherrima metabolises glycerol and a diverse range of other sugars, suggesting that heterogeneous biomass could provide a suitable carbon source. M. pulcherrima also grows well in a minimal media containing no yeast extract. Finally, we demonstrate the potential of the yeast to produce lipids inexpensively on an industrial scale by culturing the yeast in a 500 L, open air, tank reactor without any significant contamination.

Conclusions: The production of antimicrobial compounds coupled to efficient growth at low temperature and pH enables culture of this oleaginous yeast in inexpensive, non-sterile conditions providing a potential route to economic biofuel production.

No MeSH data available.


Related in: MedlinePlus

Temperature, pH and growth curve for the M. pulcherrima culture, cultivated in an open-air stirred tank reactor.
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Figure 10: Temperature, pH and growth curve for the M. pulcherrima culture, cultivated in an open-air stirred tank reactor.

Mentions: To demonstrate the suitability of M. pulcherrima for low-cost production, it was grown in a hostile environment with limited temperature control on a model waste resource. The yeast was cultured in a glycerol-based OMP media in non-sterile conditions in two 500-L raceway ponds situated in a temperature-controlled glasshouse (Figure 9). The ponds were gently agitated by a paddle wheel at 10 rpm and maintained for 15 days (Figure 10). The temperature remained roughly constant at 21°C irrespective of the conditions outside the glasshouse. During culture, M. pulcherrima was expected to regulate the pH of the medium by producing both acids and bases depending on the stage of the growth cycle. To maintain a healthy population of M. pulcherrima, while retaining acceptable rates of lipid and biomass production, pH was artificially held between 3 and 4 by the addition of weak solutions of either HCl or KOH. Although some bacteria were observed at various times over the first 72 hours of culture, the population remained overwhelmingly M. pulcherrima (as judged by flow cytometry; data not shown). After 2 weeks when the pH was manually reduced to 3, no further contamination was observed for the remainder of the culture period. When the cultures in the raceway ponds reached a value of absorbance at 600 nm of around 10, many large M. pulcherrima colonies were observed growing on the paddle wheels. These colonies developed an intense pink colour compared to the suspended culture, presumably due to increased pulcherrimin production associated with elevated levels of oxygenation [20]. Over the culture period, biomass accumulation measured by flow cytometry increased steadily reaching a final value of 2.06 g⋅L-1 (Table 2).


Low-cost lipid production by an oleaginous yeast cultured in non-sterile conditions using model waste resources.

Santamauro F, Whiffin FM, Scott RJ, Chuck CJ - Biotechnol Biofuels (2014)

Temperature, pH and growth curve for the M. pulcherrima culture, cultivated in an open-air stirred tank reactor.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4016040&req=5

Figure 10: Temperature, pH and growth curve for the M. pulcherrima culture, cultivated in an open-air stirred tank reactor.
Mentions: To demonstrate the suitability of M. pulcherrima for low-cost production, it was grown in a hostile environment with limited temperature control on a model waste resource. The yeast was cultured in a glycerol-based OMP media in non-sterile conditions in two 500-L raceway ponds situated in a temperature-controlled glasshouse (Figure 9). The ponds were gently agitated by a paddle wheel at 10 rpm and maintained for 15 days (Figure 10). The temperature remained roughly constant at 21°C irrespective of the conditions outside the glasshouse. During culture, M. pulcherrima was expected to regulate the pH of the medium by producing both acids and bases depending on the stage of the growth cycle. To maintain a healthy population of M. pulcherrima, while retaining acceptable rates of lipid and biomass production, pH was artificially held between 3 and 4 by the addition of weak solutions of either HCl or KOH. Although some bacteria were observed at various times over the first 72 hours of culture, the population remained overwhelmingly M. pulcherrima (as judged by flow cytometry; data not shown). After 2 weeks when the pH was manually reduced to 3, no further contamination was observed for the remainder of the culture period. When the cultures in the raceway ponds reached a value of absorbance at 600 nm of around 10, many large M. pulcherrima colonies were observed growing on the paddle wheels. These colonies developed an intense pink colour compared to the suspended culture, presumably due to increased pulcherrimin production associated with elevated levels of oxygenation [20]. Over the culture period, biomass accumulation measured by flow cytometry increased steadily reaching a final value of 2.06 g⋅L-1 (Table 2).

Bottom Line: This approach resulted in yields of up to 40% lipid, which compares favourably with other oleaginous microbes.We also demonstrate that M. pulcherrima metabolises glycerol and a diverse range of other sugars, suggesting that heterogeneous biomass could provide a suitable carbon source.M. pulcherrima also grows well in a minimal media containing no yeast extract.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK. R.J.Scott@bath.ac.uk.

ABSTRACT

Background: The yeast Metschnikowia pulcherrima, previously utilised as a biological control agent, was evaluated for its potential to produce lipids for biofuel production.

Results: Cultivation in low cost non-sterile conditions was achieved by exploiting its ability to grow at low temperature and pH and to produce natural antimicrobial compounds. Although not previously classified as oleaginous, a combination of low temperature and restricted nutrient availability triggered high levels of oil production in M. pulcherrima cultures. This regime was designed to trigger the sporulation process but prevent its completion to allow the accumulation of a subset of a normally transitional, but oil-rich, 'pulcherrima' cell type. This approach resulted in yields of up to 40% lipid, which compares favourably with other oleaginous microbes. We also demonstrate that M. pulcherrima metabolises glycerol and a diverse range of other sugars, suggesting that heterogeneous biomass could provide a suitable carbon source. M. pulcherrima also grows well in a minimal media containing no yeast extract. Finally, we demonstrate the potential of the yeast to produce lipids inexpensively on an industrial scale by culturing the yeast in a 500 L, open air, tank reactor without any significant contamination.

Conclusions: The production of antimicrobial compounds coupled to efficient growth at low temperature and pH enables culture of this oleaginous yeast in inexpensive, non-sterile conditions providing a potential route to economic biofuel production.

No MeSH data available.


Related in: MedlinePlus