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High concentrations of dried sorghum stalks as a biomass feedstock for single cell oil production by Rhodosporidium toruloides.

Matsakas L, Bonturi N, Miranda EA, Rova U, Christakopoulos P - Biotechnol Biofuels (2015)

Bottom Line: Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms.It was found that addition of an external nitrogen source had a negative impact on single cell oil (SCO) production yields, which has a positive effect on the process economics.Subsequently the effect of the presence of a distinct saccharification step on SCO was examined.

View Article: PubMed Central - PubMed

Affiliation: Biochemical Process Engineering, Division of Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden.

ABSTRACT

Background: Environmental crisis and concerns for energy security have made the research for renewable fuels that will substitute the usage of fossil fuels an important priority. Biodiesel is a potential substitute for petroleum, but its feasibility is hindered by the utilization of edible vegetable oil as raw material, which is responsible for a large fraction of the production cost and fosters the food versus fuel competition. Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms. Sweet sorghum is an excellent candidate as substrate for microbial oil production, as it possesses high photosynthetic activity yielding high amounts of soluble and insoluble carbohydrates, and does not require high fertilization and irrigation rates.

Results: Initially the ability of sweet sorghum to fully support yeast growth, both as a carbon and nitrogen source was evaluated. It was found that addition of an external nitrogen source had a negative impact on single cell oil (SCO) production yields, which has a positive effect on the process economics. Subsequently the effect of the presence of a distinct saccharification step on SCO was examined. The presence of an enzymatic saccharification step prior to SCO production improved the production of SCO, especially in high solid concentrations. Removal of solids was also investigated and its positive effect on SCO production was also demonstrated. When juice from 20% w/w enzymatically liquefied sweet sorghum was used as the raw material, SCO production was 13.77 g/L. To the best of our knowledge this is one of the highest SCO titers reported in the literature when renewable raw materials were utilized.

Conclusions: The use of sweet sorghum at high solid concentrations as a feedstock for the efficient production of SCO by Rhodosporidium toruloides was demonstrated. Moreover, addition of enzymes not only led to liquefaction of sweet sorghum and permitted liquid fermentation, but also enhanced lipid production by 85.1% and 15.9% when dried stalks or stalk juice was used, respectively.

No MeSH data available.


Related in: MedlinePlus

Time course of single cell oil (SCO) production on juice obtained from 20% w/w solids concentration. Time course of sugars consumption (diamond), biomass (filled circle) and lipid (circle) concentration when R. toruloides was cultivated on sweet sorghum juice that came from 20% w/w sweet sorghum concentration.
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Fig4: Time course of single cell oil (SCO) production on juice obtained from 20% w/w solids concentration. Time course of sugars consumption (diamond), biomass (filled circle) and lipid (circle) concentration when R. toruloides was cultivated on sweet sorghum juice that came from 20% w/w sweet sorghum concentration.

Mentions: For this reason, we also evaluated the effect of the removal of solids on SCO production in this study, both with and without a distinct saccharification step. We found that the removal of solids after the saccharification step resulted in enhanced SCO production even at high concentrations of sweet sorghum, such as 20% w/w (Figure 3). The cell growth, sugar consumption, and lipid production at a solids concentration of 20% are shown as a function of time in Figure 4. It is worth mentioning that glucose and fructose co-utilized almost at the same rate, whereas sucrose was totally hydrolyzed by the invertase activity exhibited by Novozym®188 to glucose and fructose (data not shown). The maximum lipid concentration (13.77 g/L) with lipid content of 33.1% w/w was observed on day 10. This production value is higher than most of the SCO concentrations reported in the literature when renewable resources have been used as raw materials (Table 1). Moreover, in this work an enzymatic treatment of an energy crop was used, which offers advantages over the acid hydrolysis of lignocellulosic materials such as low energy consumption due to the mild process requirements, high sugar yields, no requirement for detoxification, and no unwanted wastes. The SCO yield was equal to 0.105 g/g of consumed sugars, whereas the biomass formation yield was 0.318 g/g, and the lipid productivity reached 1.377 g/L per day. The use of an enzymatic saccharification step resulted in an increase in SCO production of 15.9% relative to the experiment without enzymatic saccharification.Figure 3


High concentrations of dried sorghum stalks as a biomass feedstock for single cell oil production by Rhodosporidium toruloides.

Matsakas L, Bonturi N, Miranda EA, Rova U, Christakopoulos P - Biotechnol Biofuels (2015)

Time course of single cell oil (SCO) production on juice obtained from 20% w/w solids concentration. Time course of sugars consumption (diamond), biomass (filled circle) and lipid (circle) concentration when R. toruloides was cultivated on sweet sorghum juice that came from 20% w/w sweet sorghum concentration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4308834&req=5

Fig4: Time course of single cell oil (SCO) production on juice obtained from 20% w/w solids concentration. Time course of sugars consumption (diamond), biomass (filled circle) and lipid (circle) concentration when R. toruloides was cultivated on sweet sorghum juice that came from 20% w/w sweet sorghum concentration.
Mentions: For this reason, we also evaluated the effect of the removal of solids on SCO production in this study, both with and without a distinct saccharification step. We found that the removal of solids after the saccharification step resulted in enhanced SCO production even at high concentrations of sweet sorghum, such as 20% w/w (Figure 3). The cell growth, sugar consumption, and lipid production at a solids concentration of 20% are shown as a function of time in Figure 4. It is worth mentioning that glucose and fructose co-utilized almost at the same rate, whereas sucrose was totally hydrolyzed by the invertase activity exhibited by Novozym®188 to glucose and fructose (data not shown). The maximum lipid concentration (13.77 g/L) with lipid content of 33.1% w/w was observed on day 10. This production value is higher than most of the SCO concentrations reported in the literature when renewable resources have been used as raw materials (Table 1). Moreover, in this work an enzymatic treatment of an energy crop was used, which offers advantages over the acid hydrolysis of lignocellulosic materials such as low energy consumption due to the mild process requirements, high sugar yields, no requirement for detoxification, and no unwanted wastes. The SCO yield was equal to 0.105 g/g of consumed sugars, whereas the biomass formation yield was 0.318 g/g, and the lipid productivity reached 1.377 g/L per day. The use of an enzymatic saccharification step resulted in an increase in SCO production of 15.9% relative to the experiment without enzymatic saccharification.Figure 3

Bottom Line: Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms.It was found that addition of an external nitrogen source had a negative impact on single cell oil (SCO) production yields, which has a positive effect on the process economics.Subsequently the effect of the presence of a distinct saccharification step on SCO was examined.

View Article: PubMed Central - PubMed

Affiliation: Biochemical Process Engineering, Division of Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden.

ABSTRACT

Background: Environmental crisis and concerns for energy security have made the research for renewable fuels that will substitute the usage of fossil fuels an important priority. Biodiesel is a potential substitute for petroleum, but its feasibility is hindered by the utilization of edible vegetable oil as raw material, which is responsible for a large fraction of the production cost and fosters the food versus fuel competition. Microbial oils are an interesting alternative as they do not compete with food production, and low cost renewable materials could serve as raw materials during cultivation of microorganisms. Sweet sorghum is an excellent candidate as substrate for microbial oil production, as it possesses high photosynthetic activity yielding high amounts of soluble and insoluble carbohydrates, and does not require high fertilization and irrigation rates.

Results: Initially the ability of sweet sorghum to fully support yeast growth, both as a carbon and nitrogen source was evaluated. It was found that addition of an external nitrogen source had a negative impact on single cell oil (SCO) production yields, which has a positive effect on the process economics. Subsequently the effect of the presence of a distinct saccharification step on SCO was examined. The presence of an enzymatic saccharification step prior to SCO production improved the production of SCO, especially in high solid concentrations. Removal of solids was also investigated and its positive effect on SCO production was also demonstrated. When juice from 20% w/w enzymatically liquefied sweet sorghum was used as the raw material, SCO production was 13.77 g/L. To the best of our knowledge this is one of the highest SCO titers reported in the literature when renewable raw materials were utilized.

Conclusions: The use of sweet sorghum at high solid concentrations as a feedstock for the efficient production of SCO by Rhodosporidium toruloides was demonstrated. Moreover, addition of enzymes not only led to liquefaction of sweet sorghum and permitted liquid fermentation, but also enhanced lipid production by 85.1% and 15.9% when dried stalks or stalk juice was used, respectively.

No MeSH data available.


Related in: MedlinePlus