Ethanol Production from Yeasts

Organization of Advanced Science and Technoiogy, Kobe University, Nada, Kobe, Japan AKIHIKO KONDO 

2 Yeast CeU-Surface Engineering System for Biomass Utilization 

3 Ethanol Production from Starchy Biomass Using Amylase-Expressing Yeast Ethanol Production from LignoceUulosic Biomass 

1 Ethanol Production from Cellulase-Secreting Yeast 

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A summary of the factors which are known to influence ethanol production from glucose in a gas-solid fluidized bed fermenter, or which may have an influence based on observations with submerged fermentations, is shown in Figure 6.1. In anaerobic beds, the key factors are the fermentation temperature and ethanol inhibition, both of which have a dramatic effect on the specific rafe of ethanol production. Bed dehydration and its influence on yeast pellet moisture content is also important, since a failure of fermentation may occur if the pellets become too dry (Bauer, 1986). 

Figure 6.1 Factors affecting ethanol production from glucose using baker s yeast (S. cerevisiae) in a gas-solid fluidized bed fermenter. Reproduced from Hayes (1998) with permission.

FIGURE 7.1 Stages in ethanol production from Jerusalem artichoke using (a) acid or enzymatic hydrolysis followed by fermentation with classical yeasts (e.g., S. cerevisiae) or the bacteria Z. mobilis, and (b) inulinase-producing yeast (e.g., K. marxianus). 

Guiraud, J.P., Deville-Duc, T., and Galzy, P., Selection of yeast strains for ethanol production from inulin,... 

Margaritis, A., Bajpai P., and Bajpai, P.K., Fuel ethanol production from Jerusalem artichoke stalks using different yeasts, Dev. Ind. Microbiol. Ser., 24, 321-327, 1983a. 

Ethanol Production in Yeast When grown anaerobically on glucose, yeast (S. cerevisiae) converts pyruvate to acetaldehyde, then reduces acetaldehyde to ethanol using electrons from NADH. Write the equation for the second reaction, and calculate its equilibrium constant at 25 °C, given the standard reduction potentials in Table 13-7. 

Dekker, R. F. H. 1982. Ethanol production from D-xylose and other sugars by the yeast Pachysolen tannophilus. Biotechnol. Lett., 4, 411 16. 

Various bacteria, and particularly the lactobadlfi, have been reported to use phosphoketolase (EC 4.1.2.9) during the metabofism of xylose [123-126]. Phosphoketolase has been reported in a few aerobic yeasts that use xylose rapidly [127-129], and the capacity of a Candida sp. to accumulate lipid has been attributed to its presence [130]. However, a role for this enzyme in ethanol production from xylose has not been estabfished. 

A more detailed study of this yeast was reported by Slininger et al. [85]. According to the reported literature, ethanol production from xylose by P. tannophilus exhibits the following characteristics ... 

Pichia stipitis. P. stipitis is the most effective natural yeast for the conversion of xylose to ethanol. This yeast species shares many characteristics with its close relative, C. shehatae. Toivola et al. [90] performed a systemic screening program with type strains of some 200 yeast species and identified P. stipitis as one of the yeast species that produces ethanol from xylose. There are many studies that have explored the property of this yeast in relation to its oxygen requirement, ethanol tolerance, enzyme cofactor s balance, etc. According to the reported literature [91,92], ethanol production from xylose by P stipitis exhibits the following characteristics ... 

Little attention has been focused on the fermentation of L-arabinose to ethanol. Recently, McMillan and Boynton [100] evaluated eight fungal and six yeast strains for ethanol production from arabinose under oxygen-limited conditions. None of the strains tested produced ethanol from arabinose. They utihz-ed arabinose for cell biomass and L-arabitol production. 

Candida shehatae. The abihty of C. shehatae to produce ethanol from xylose was first reported by du Preez and van der Walt [86] in 1983. Since then, many studies have been conducted related to the property of this yeast. According to the reported hterature [87-89], ethanol production from xylose by C. shehatae exhibits the fohowing characteristics ... 

More recently, an ethanol-tolerant industrial yeast was used as host for the creation of a recombinant xylose-fermenting strain by expression of XYLl, XYL2, and XKSl, integrated into the yeast s genomic HIS3 locus (Cordero Otero, unpubhshed results). The recombinant strain demonstrated ethanol production from xylose in a defined medium... 

Chiang LC, Hsiao HY, Ueng PP, Chen LF,Tsao GT (1982) Ethanol production from xylose by enzymic isomerization and yeast fermentation. In Scott CD (ed) Biotechnol Bioeng Symp. Wiley, New York, p 263... 

The viability of the yeast cells, and thus the reduced toxicity of the entrapment method, can be demonstrated by cell growth In the matrix, which gives rise to a corresponding activity Increase for ethanol production from glucose (J) This behavior Is shown In Figure A. The factor of activity Increase compared to the Initial value Increases with decreasing Initial loading however. 

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