title: High concentrations of dried sorghum stalks as a biomass feedstock for single cell oil production by Rhodosporidium toruloides.
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.
authors: Biochemical Process Engineering, Division of Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden.
authors: Leonidas
authors: L
authors: Matsakas
authors: Biochemical Process Engineering, Division of Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden ; Department of Materials and Bioprocess Engineering, School of Chemical Engineering, State University of Campinas, Av. Albert Einstein, 500, 13083-852 Campinas, SP Brazil.
authors: Nemailla
authors: N
authors: Bonturi
authors: Department of Materials and Bioprocess Engineering, School of Chemical Engineering, State University of Campinas, Av. Albert Einstein, 500, 13083-852 Campinas, SP Brazil.
authors: Everson Alves
authors: EA
authors: Miranda
authors: Biochemical Process Engineering, Division of Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden.
authors: Ulrika
authors: U
authors: Rova
authors: Biochemical Process Engineering, Division of Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden.
authors: Paul
authors: P
authors: Christakopoulos
keywords: Biodiesel; Enzymatic saccharification; Rhodosporidium toruloides; Single cell oil; Sweet sorghum
references: Appl Biochem Biotechnol. 2014 Aug;173(8):2086-98
references: 24928546
references: Appl Microbiol Biotechnol. 2013 Jul;97(14):6581-8
references: 23728238
references: Biomed Res Int. 2014;2014:731731
references: 25210715
references: Bioresour Technol. 2008 Sep;99(13):5923-7
references: 18420404
references: Bioresour Technol. 2011 Oct;102(19):9216-22
references: 21757339
references: Bioresour Technol. 2011 May;102(10):6134-40
references: 21463940
references: J Ind Microbiol Biotechnol. 2010 Jun;37(6):581-5
references: 20204452
references: Biotechnol Biofuels. 2011 Jan 26;4(1):2
references: 21269447
references: Appl Microbiol Biotechnol. 2008 Oct;80(5):749-56
references: 18690426
references: Appl Microbiol Biotechnol. 2011 May;90(4):1219-27
references: 21465305
references: Bioresour Technol. 2010 Aug;101(15):6124-9
references: 20307977
references: Bioresour Technol. 2013 Jan;127:202-8
references: 23131642
references: Bioresour Technol. 2010 May;101(10):3623-7
references: 20079633
references: Bioresour Technol. 2013 Sep;144:360-9
references: 23891835
references: Bioresour Technol. 2009 Oct;100(19):4535-8
references: 19433350
references: J Biol Chem. 1957 May;226(1):497-509
references: 13428781
references: Bioresour Technol. 2010 Feb;101(4):1385-8
references: 19781936
references: N Biotechnol. 2012 Feb 15;29(3):372-8
references: 21458601