Ethanol-from-cellulose

The commercial production of cellulosic ethanol is moving closer with advances in technology along with federal and private funding for new plants and research centers. These are accelerating the time to volume production which could push the cost of ethanol from cellulosic feedstocks to well under 1.00 a gallon below the cost of corn ethanol. 

Lynd, LR et al., Fuel Ethanol from Cellulosic Biomass, Science, 251(4999), 1318-1323 (1991)... 

Production of Ethanol from Cellulosic Biomass Hydrolysates Using Genetically Engineered Saccharomyces Yeast Capable of Cofermenting Glucose and Xylose... 

Sedlak, M. and Ho,N.W.Y. (2004). Production of Ethanol From Cellulosic Biomass Hydrolysates Using Genetically Engineered Saccharomyces Yeast Capable of Cofermenting Glucose and Xylose. Appl. Biochem. Biotechnol., 113-116, 403-416. 

Ethanol from Cellulose Feedstock Power Generation from Biomass... 

Lynd, L.R., Cushman, J.H., Nichols, R.J., and Wyman, C.E. 1991. Fuel ethanol from cellulosic biomass. Science, 251 1318-1323. 

The first plant for producing ethanol from cellulose was constructed in South Carolina in 1910 the yield was approximately 83 L/t (20 gal/ton) of sawdust (Fieser and Fieser, 1950). Hydrolysis of sawdust was accomplished... 

Badger, P.C. Ethanol from cellulose a general review. In Trends in New Crops and New Uses, Janick, J., Whipkey, A., Eds. ASMS Press Alexandria, VA, 2002 17-21. 

Ethanol from cellulose represents an enormous opportunity to make a transportation fuel that is an alternative to gasoline. Development of such a fuel is motivated by 1) an increased cleanliness of automobile exhaust, with decreased levels of carbon monoxide and nitrous oxides, 2) a need for a fuel that does not contribute to an increase in the Greenhouse effect, 3) the desire to decrease the dependence of the United States on imported petroleum, and 4) the possibility of creating wealth in regions where cellulose is a prevalent natural resource. 

In addition to ethanol from cellulose, cellulase enzymes play a minor role in the production of ethanol from corn. In this process, most of the glucose is from starch. Cellulase enzymes offer the opportunity to increase the glucose yield by hydrolyzing a portion of the cellulose to glucose, as well as decreasing the viscosity of the ground corn [25]. 

Processes for the bioproduction of ethanol from cellulosic materials have been studied extensively. Some of the process steps are specialized and beyond the scope of this chapter. However, there are many recent review articles dealing with some specific subjects. Basically, the processes consist of a number of steps. They are availability and collection of raw feedstock [20], size reduction, pretreatment, fractionation of biomass components, enzyme production [21, 22], saccharification, enzyme recycle [23, 24], pentose fermentation, improvement of pentose-fermenting biocatalyst, overcoming of product inhibition, overcoming inhibition by substrate-derived inhibitors, ethanol recovery [25], steam generation and recycling [26], waste treatment, and by-product utilization. 

SSF is a process in which the production of ethanol from cellulosic materials is achieved by utilizing cellulose, cellulase, ethanol-producing microbes and nutrients in the same reactor. This process is desirable because the continuous removal of sugars by fermentative organisms alleviates end-product inhibition of enzyme hydrolysis of cellulose. The process is also simplified because only one reactor is used. The SSF process for ethanol production from cellulosic materials was reported by Blotkamp et al. [65] and was later tested on a pilot scale (for detail, see [66]). 

In designing an efficient SSF system for the conversion of cellulose to ethanol, the fermentation temperature should be compatible with the saccharification temperature that is generally between 45 and 55 °C. The optimal temperature for the most commonly available cellulase is about 50 °C. Therefore, the use of high-temperature-tolerant microbes is desirable for the application of the SSF process to ethanol production. Typical industrial ethanol-producing yeast strains are mesophiHc with an optimal fermentation temperature of 30-37°C. Only a few yeast strains that are thermotolerant, as well as good ethanol fermenters, have been described. However, some thermophilic bacterial species are known to produce ethanol from cellulosic-derived carbohydrates [68,69]. 

Ethanol by continuous fomentation. Europ. Cham. News, Biotechnology Suppi- 20-21, (May 1983). Nystrom. 3. M., Greenwald. C. G- Harrison. F. G-, Gibson. ED. Making ethanol from celluloses", Chem, Engng Progress, 80 (5) 68 74 (19841. 

According to a recent conference given by Prof. Kita [162], the classical synthesis method currently used by Mitsui allows to produce about 250 zeolite membranes per day. Both the LTA and T types (Na K) membranes are now commercial and more than 80 pervaporation and vapor permeation plants are operating in Japan for the dehydration of organic liquids [163]. A typical pervaporation system, similar to the one described in [8], is shown in Fig. 11. One of the most recent applications concerns the production of fuel ethanol from cellulosic biomass by a vapour permeation/ pervaporation combined process. The required heat is only 1 200 kcal per liter of product, i.e. half of that of the classical process. Mitsui has recently installed a bio-ethanol pilot plant based on tubular LTA membranes in Brazil (3 000 liters/day) and a plant with 30 000 liters/day has been erected in India. The operating temperature is 130 °C, the feed is 93 % ethanol, the permeate is water and the membrane selectivity is 10 000. 

The cellulolytic fungus Trichoderma reesei is well known to produce stable cellulase useful for saccharification of cellulose and is widely used for production of commercial cellulase [1, 2], Fuel ethanol must be produced from cellulosic resources to prevent global warming [3]. The cellulase of this fungus is applicable for producing ethanol from cellulosic materials, but the cost is still a problem [4], Thus, the cellulase productivity of this fungus... 

Lynd, L.R. (1996) Overview and evaluation of fuel ethanol from cellulosic biomass technology, economics, the... 

Figure 4.6 Coproduction of synthetic amylose and ethanol from cellulose via multi-enzymes and an ethanol-producing yeast. EG endoglucanase, CBH cellobiohydrolase, CBP cellohiose phosphorylase, PGP potato a-glucan phosphorylase.

Garhyan, P., and Elnashaie, S. S. E. H. Integrated multidisciplinary approach for efficient production of fuel ethanol from cellulosic waste. International Conference on Fiber Industry, 2002. 

The bioconversion of cellulose into ethanol with conventional methods is usually achieved in two steps first being the enzymatic saccharification of the polysaccharide to monosaccharide and secondly the bioconversion of monosaccharides into ethanol. A combination of enzymatic hydrolysis and ethanol production in the same reactor has been attempted using different cellulases and ethanol producing microbial species to improve process efficiency [46-53]. The production of ethanol from cellulose in a simultaneous saccharification and biological conversion process alleviates the problem of end product inhibition, since glucose does not accumulate in this system and is converted to ethanol immediately following saccharification [46]. 

It is possible to convert cellulose into fermentable glucose. Comment on the consequence of an economical process being developed that can produce ethanol from cellulose based crops. Comment on the difference between ethanol and methanol with regard to price and suitability as a... 

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