Study of flocculent yeast performance in tower reactors for bioethanol production in a continuous fermentation process with no cell recycling

Andrietta, Sílvio Roberto; Steckelberg, Cláudia; Andrietta, Maria da Graça Stupiello

doi:10.1016/j.biortech.2007.06.037

Cited by 30 publications

(24 citation statements)

References 13 publications

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“…90 Other bioreactor confi gurations like fl uidized bed reactor and tower reactor confi gurations have also been investigated for ethanol productivity and yield. 91,92 Ethanol In situ ethanol removal from the fermentation broth has been found to be useful in increasing ethanol volumetric productivity and reducing process costs due to reduced ethanol inhibition of the fermenting strains. In situ ethanol separation can take place by virtue of reaction-separation integration.…”

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confidence: 99%

Commercializing lignocellulosic bioethanol: technology bottlenecks and possible remedies

Banerjee

Mudliar²,

Sen

et al. 2009

Biofuels Bioprod Bioref

317

176

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With diminishing oil supplies and growing political instability in oil-producing nations, the world is facing a major energy threat which needs to be solved by virtue of alternative energy sources. Bioethanol has received considerable attention in the transportation sector because of its utility as an octane booster, fuel additive, and even as neat fuel. Brazil and the USA have been producing ethanol on a large scale from sugarcane and corn, respectively. However, due to their primary utility as food and feed, these crops cannot meet the global demand for ethanol production as an alternative transportation fuel. Lignocellulosic biomass is projected as a virtually eternal raw material for fuel ethanol production. The main bottleneck so far has been the technology concerns, which do not support cost-effective and competitive production of lignocellulosic bioethanol. This review sheds light on some of the practical approaches that can be adopted to make the production of lignocellulosic bioethanol economically attractive. These include the use of cheaper substrates, cost-effective pre-treatment techniques, overproducing and recombinant strains for maximized ethanol tolerance and yields, improved recovery processes, effi cient bioprocess integration, economic exploitation of side products, and energy and waste minimization. An integrated and dedicated approach can help in realizing large-scale commercial production of lignocellulosic bioethanol, and can contribute toward a cleaner and more energy effi cient world.

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mentioning

confidence: 99%

Commercializing lignocellulosic bioethanol: technology bottlenecks and possible remedies

Banerjee

Mudliar²,

Sen

et al. 2009

Biofuels Bioprod Bioref

317

176

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“…[1][2][3][4] In addition, flocculating yeast cells are useful in immobilized cell systems with no inert support materials. 5) However, although flocculation mechanisms and the introduction of this property to non-flocculent yeast strains have been extensively studied in S. cerevisiae, few studies of this nature have been undertaken in other yeast species. 6,7) The mechanism of yeast flocculation involves the interaction of lectin-like proteins, called flocculins, with receptors on a neighboring cell wall, resulting in the formation of aggregates.…”

mentioning

confidence: 99%

Construction of FlocculentKluyveromyces marxianusStrains Suitable for High-Temperature Ethanol Fermentation

Nonklang

Ano²,

Abdel-Banat

et al. 2009

Bioscience, Biotechnology, and Biochemistry

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Flocculating yeasts are highly useful in fermentation processes because these cells can be separated easily from the fermentation mash. However, native yeasts are usually non-flocculating, including Kluyveromyces marxianus, which exhibits a potent high-temperature ethanol fermentation ability. We describe here the construction of flocculent K. marxianus strains via the introduction of the FLO1, FLO5, FLO9, and FLO10 genes from Saccharomyces cerevisiae. The S. cerevisiae FLO genes were overexpressed by upstream insertion of the constitutive TDH3 promoter, resulting in flocculent S. cerevisiae strains. These TDH3p-FLO sequences were then amplified by PCR and introduced directly into a K. marxianus strain. These K. marxianus strains showed a flocculation phenotype, indicating that the introduced S. cerevisiae TDH3 promoter and all FLO genes were functional in this strain. Moreover, a flocculating K. marxianus strain showed the same ethanol production profile as that of its wild-type parent. The K. marxianus flocculating strains we generated should be useful in the future development of cost-effective fed-batch and continuous fermentation systems at high temperatures.Key words: Kluyveromyces marxianus; yeast; flocculation; ethanol fermentationFlocculation is an attractive property in industrial yeasts because the cells can be easily separated from a fermentation mash. The application of flocculating strains to industrial fermentation processes removes the need for extensive and costly cell separation equipment, and these yeasts are thus suitable for both fedbatch and continuous fermentation. [1][2][3][4] In addition, flocculating yeast cells are useful in immobilized cell systems with no inert support materials. 5) However, although flocculation mechanisms and the introduction of this property to non-flocculent yeast strains have been extensively studied in S. cerevisiae, few studies of this nature have been undertaken in other yeast species. 6,7) The mechanism of yeast flocculation involves the interaction of lectin-like proteins, called flocculins, with receptors on a neighboring cell wall, resulting in the formation of aggregates. [8][9][10][11] Environmental factors such as pH, calcium, and organic stress also affect flocculation. 9,[12][13][14] The five FLO genes, FLO1, FLO5, FLO9, FLO10, and FLO11, have been described in S. cerevisiae thus far. [15][16][17][18][19] The FLO1, 5, 9, and 10 genes confer cell-cell adhesion (flocculation) ability, whereas FLO11 is responsible for substrate adhesion. 20) FLO1, FLO5, and FLO9 are highly similar to each other, but FLO10 has lower similarity. The mechanisms of flocculation in other yeasts appear to be lectin-based but of differing specificities. For instance, galactose and its derivatives have been found to inhibit flocculation of K. bulgaricus and K. lactis, suggesting that this interaction involves a galactose-specific lectin. 21,22) The advantages of using flocculating yeast cells in fermentation processes have led to many studies on the construction of flocculent s...

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“…Yeast colonies were selected based on their cell morphology in Wallerstein Laboratory Nutrient Agar cultivation medium (WL nutrient medium -DIFCO 0424-17-9) when grown for 7 days at 32 o C. Yeast strains present at concentrations higher than 10 6 CUF/ml of sample were selected. Strain differentiation was performed with the use of karyotyping (Andrietta et al, 2008). Yeast population dynamics during the season, for a certain industrial plant, herein designated Unit A, is shown in Figure 3.…”

Section: Strainmentioning

confidence: 99%

Bioethanol – What Has Brazil Learned About Yeasts Inhabiting the Ethanol Production Processes from Sugar Cane?

Andrietta¹,

Andrietta²,

Stupiello³

2011

Biofuel Production-Recent Developments and Prospects

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Study of flocculent yeast performance in tower reactors for bioethanol production in a continuous fermentation process with no cell recycling

Cited by 30 publications

References 13 publications

Commercializing lignocellulosic bioethanol: technology bottlenecks and possible remedies

Commercializing lignocellulosic bioethanol: technology bottlenecks and possible remedies

Construction of FlocculentKluyveromyces marxianusStrains Suitable for High-Temperature Ethanol Fermentation

Bioethanol – What Has Brazil Learned About Yeasts Inhabiting the Ethanol Production Processes from Sugar Cane?

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