Construction of a flocculating yeast for fuel ethanol production

Wang, Fu-Zhuan; Shen, Wei; Rao, Zhiming; Fang, Huiying; Zhan, Xi; Zhuge, Jian

doi:10.1007/s10529-007-9503-6

Cited by 17 publications

(10 citation statements)

References 14 publications

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“…The flocculation assay was performed according to Wang et al (2008), with some modifications. After growth in the multiplication medium (sugar cane juice with around 4% of reducing sugars), the cells were collected by centrifugation, washed twice with sodium citrate buffer (50 mM; pH 3.0) containing 5 mM EDTA and washed again with water at 4 °C.…”

Section: Methodsmentioning

confidence: 99%

Characteristics of Saccharomyces cerevisiae yeasts exhibiting rough colonies and pseudohyphal morphology with respect to alcoholic fermentation

Reis¹,

Bassi²,

Silva³

et al. 2013

Braz. J. Microbiol.

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Among the native yeasts found in alcoholic fermentation, rough colonies associated with pseudohyphal morphology belonging to the species Saccharomyces cerevisiae are very common and undesirable during the process. The aim of this work was to perform morphological and physiological characterisations of S. cerevisiae strains that exhibited rough and smooth colonies in an attempt to identify alternatives that could contribute to the management of rough colony yeasts in alcoholic fermentation. Characterisation tests for invasiveness in Agar medium, killer activity, flocculation and fermentative capacity were performed on 22 strains (11 rough and 11 smooth colonies). The effects of acid treatment at different pH values on the growth of two strains (“52” - rough and “PE-02” - smooth) as well as batch fermentation tests with cell recycling and acid treatment of the cells were also evaluated. Invasiveness in YPD Agar medium occurred at low frequency; ten of eleven rough yeasts exhibited flocculation; none of the strains showed killer activity; and the rough strains presented lower and slower fermentative capacities compared to the smooth strains in a 48-h cycle in a batch system with sugar cane juice. The growth of the rough strain was severely affected by the acid treatment at pH values of 1.0 and 1.5; however, the growth of the smooth strain was not affected. The fermentative efficiency in mixed fermentation (smooth and rough strains in the same cell mass proportion) did not differ from the efficiency obtained with the smooth strain alone, most likely because the acid treatment was conducted at pH 1.5 in a batch cell-recycle test. A fermentative efficiency as low as 60% was observed with the rough colony alone.

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Section: Methodsmentioning

confidence: 99%

Characteristics of Saccharomyces cerevisiae yeasts exhibiting rough colonies and pseudohyphal morphology with respect to alcoholic fermentation

Reis¹,

Bassi²,

Silva³

et al. 2013

Braz. J. Microbiol.

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“…A number of recombinant flocculating yeast strains have been developed, e.g. with constitutive flocculation [6, 75] or with inducible flocculation by expression under control of the TPS1 promoter [76], the TPI1 promoter [77] or the ADH2 promoter [78].…”

Section: Advantages Of High Local Cell Densitymentioning

confidence: 99%

Current progress in high cell density yeast bioprocesses for bioethanol production

Westman

Franzén

2015

Biotechnology Journal

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High capital costs and low reaction rates are major challenges for establishment of fermentation‐based production systems in the bioeconomy. Using high cell density cultures is an efficient way to increase the volumetric productivity of fermentation processes, thereby enabling faster and more robust processes and use of smaller reactors. In this review, we summarize recent progress in the application of high cell density yeast bioprocesses for first and second generation bioethanol production. High biomass concentrations obtained by retention of yeast cells in the reactor enables easier cell reuse, simplified product recovery and higher dilution rates in continuous processes. High local cell density cultures, in the form of encapsulated or strongly flocculating yeast, furthermore obtain increased tolerance to convertible fermentation inhibitors and utilize glucose and other sugars simultaneously, thereby overcoming two additional hurdles for second generation bioethanol production. These effects are caused by local concentration gradients due to diffusion limitations and conversion of inhibitors and sugars by the cells, which lead to low local concentrations of inhibitors and glucose. Quorum sensing may also contribute to the increased stress tolerance. Recent developments indicate that high cell density methodology, with emphasis on high local cell density, offers significant advantages for sustainable second generation bioethanol production.

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“…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.…”

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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Construction of a flocculating yeast for fuel ethanol production

Cited by 17 publications

References 14 publications

Characteristics of Saccharomyces cerevisiae yeasts exhibiting rough colonies and pseudohyphal morphology with respect to alcoholic fermentation

Characteristics of Saccharomyces cerevisiae yeasts exhibiting rough colonies and pseudohyphal morphology with respect to alcoholic fermentation

Current progress in high cell density yeast bioprocesses for bioethanol production

Construction of FlocculentKluyveromyces marxianusStrains Suitable for High-Temperature Ethanol Fermentation

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