| 1. |
- Krikigianni, Eleni, et al.
(författare)
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Investigating the Bioconversion Potential of Volatile Fatty Acids: Use of Oleaginous Yeasts Rhodosporidium toruloides and Cryptococcus curvatus towards the Sustainable Production of Biodiesel and Odd-Chain Fatty Acids
- 2022
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 12:13
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Tidskriftsartikel (refereegranskat)abstract
- Oleaginous yeasts have attracted increasing scientific interest as single cell oil (SCO) producers. SCO can be used as a fossil-free fuel substitute, but also as a source of rarely found odd-chain fatty acids (OCFAs), such as C15, C17, and C25 fatty acids which have a wide range of nutritional and biological applications. Volatile fatty acids (VFAs) have gained interest as sustainable carbon source for yeasts. This study aims to improve current knowledge on yeast species that yield high amounts of SCO using VFAs as a carbon source. Specifically, the growth of the promising yeasts Cryptococcus curvatus and Rhodotorula toruloides was evaluated on individual VFAs, such as acetic, propionic, and butyric acid. C. curvatus proved to be more tolerant in higher concentrations of VFAs (up to 60 g/L), while butyric acid favored biomass and lipid conversion (0.65 and 0.23 g/gsubstrate, respectively). For R. toruloides, butyric acid favored biomass conversion (0.48 g/gsubstrate), but lipid conversion was favored using acetic acid, instead (0.14 g/gsubstrate). Propionic acid induced the formation of OCFAs, which yielded higher amounts for C. curvatus (up to 2.17 g/L). VFAs derived from the anaerobic digestion of brewer’s spent grain were tested as a cost-competitive carbon source and illustrated the significance of the combination of different VFAs in the quality of the produced SCO, by improving the biodiesel properties and OCFAs production.
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| 2. |
- Patel, Alok, Dr. 1989-, et al.
(författare)
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Bioprocessing of volatile fatty acids by oleaginous freshwater microalgae and their potential for biofuel and protein production
- 2022
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Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 438
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Tidskriftsartikel (refereegranskat)abstract
- To address the issue of high organic carbon costs in heterotrophic cultivation of microalgae, we evaluated the hypotheses by employing microalgae as a biorefinery for proteins and advanced biofuels after cultivation on volatile fatty acids (VFAs) instead of pure glucose. To prevent the inhibitory effect of VFAs on lipid synthesis, strains capable of tolerating high levels of VFAs were selected. Growth and lipid synthesis by two freshwater microalgae, Auxenochlorella protothecoides and Chlorella sorokiniana, was optimized at different VFA concentrations. Maximum biomass and lipid content in A. protothecoides (10.66 g/L, 33.93%) and C. sorokiniana (7.98 g/L, 39.80%) were obtained by replacing glucose with 30 g/L acetate at C/N 60. The generated lipids were compliant with existing standards for biodiesel. Moreover, when grown on acetate, both microalgae contained the complete range of essential and non-essential amino acids. Finally, single-source commercial VFAs were replaced with VFAs mixture after acidogenic fermentation of waste lignocellulosic biomass from brewers’ spent grain. The mixture allowed successful mixotrophic and heterotrophic cultivation of both microalgae, demonstrating feasibility of this low-cost carbon source in fuel-grade biodiesel production.
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| 3. |
- Vyas, Sachinkumar Rajendrakumar, et al.
(författare)
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Biosynthesis of microalgal lipids, proteins, lutein, and carbohydrates using fish farming wastewater and forest biomass under photoautotrophic and heterotrophic cultivation
- 2022
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Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 359
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Tidskriftsartikel (refereegranskat)abstract
- Biorefineries enable the circular, sustainable, and economic use of waste resources if value-added products can be recovered from all the generated fractions at a large-scale. In the present studies the comparison and assessment for the production of value-added compounds (e.g., proteins, lutein, and lipids) by the microalga Chlorella sorokiniana grown under photoautotrophic or heterotrophic conditions was performed. Photoautotrophic cultivation generated little biomass and lipids, but abundant proteins (416.66 mg/gCDW) and lutein (6.40 mg/gCDW). Heterotrophic conditions using spruce hydrolysate as a carbon source favored biomass (8.71 g/L at C/N 20 and 8.28 g/L at C/N 60) and lipid synthesis (2.79 g/L at C/N 20 and 3.61 g/L at C/N 60) after 72 h of cultivation. Therefore, heterotrophic cultivation of microalgae using spruce hydrolysate instead of glucose offers a suitable biorefinery concept at large-scale for biodiesel-grade lipids production, whereas photoautotrophic bioreactors are recommended for sustainable protein and lutein biosynthesis.
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