Ethanol fermentation sources

Figure 9.10 Flow chart of an ethanol fermentation plant. (Source United States. National Agricultural Library Office of Alcohol Fuels Solar Energy Research Institute. Fuel from Farms A Guide to Small-Scale Ethanol Production. Golden, Colo. Technical Information Office, Solar Energy Research Institute, 1982 published at www //dnr.state.Ia.us.)...

Use Manufacture of formaldehyde, acetic acid, and dimethyl terephthalate chemical synthesis (methyl amines, methyl chloride, methyl methacrylate) antifreeze solvent for nitrocellulose, ethylcellulose, polyvinyl butyral, shellac, rosin, manila resin, dyes denaturant for ethanol dehydrator for natural gas fuel for utility plants (methyl fuel) feedstock for manufacture of synthetic proteins by continuous fermentation source of hydrogen for fuel cells home-heating-oil extender. 

Before 1945, most of the supply of ethyl alcohol for industrial solvent or feedstock uses was derived from fermentation (Table 16.13). Since this time, the reliability and low cost of petrochemical routes to the product caused a rapid displacement of fermentation sources in the U.S. Since 1975, however, subsidies for fermentation alcohol have changed this. Large new fermentation units have been constructed, and distilleries formerly used for spirits production have been converted to industrial alcohol production [56]. Increased costs of American synthetic ethanol have kept its production at two-thirds of the total. The early petrochemical sources were based on the formation and hydrolysis of ethyl sulfate, but in North America, this has been replaced by the direct gas phase hydration of ethylene (Eqs. 16.18-16.20). 

Although this method is capable of well over 90% yields of ethylene, and may be used when the local availability and price of ethanol (e.g., occasionally fermentation sources, Brazil) are attractive, other methods are usually more important. 

Table VI shows the results of the three continuous fermentations completed with the r424A organism. The carbon source in the fermentation media was corn fiber hydrolysate produced by the initial hydrolysis method followed by secondary acid hydrolysis. The yeast metabolized over 60% of the total carbohydrates with a g ethanol/g carbohydrate yield between 0.50 and 0.55. The lower percentage of total carbohydrates metabolized is likely due to the continuous fermentation method, as shake flask fermentations, albeit at lower dry solids, metabolized up to 91% of the carbohydrates (unpublished data). The carbohydrate utilization will be optimized in future fermentations. The g/g yield is near theoretical, therefore the metabolized carbohydrate is converted solely to ethanol. The organic acids, ethanol and dextrose concentrations for a sample fermentation are shown in Figure 1. The ethanol concentration in the fermentor at the end of the run was 55g/L. The concentrations of the citric acid, lactic acid and glycerol increase substantially during the fermentation, which are normal byproducts of the ethanol fermentation by Saccharomyces cerevisiae. The volume of the fermentation was doubled with hydrolysate fed into the fermentor. These fermentations show that the organism can ferment the glucose and xylose from the corn fiber hydrolysate to ethanol without detoxification of the hydrolysate. The fermentation conditions were not optimized, so additional improvement in the fermentation is expected.

Screenwashes were typically 50 50 methanol and water but now usually contain typically 10-50% isopropanol although some mixed propanols are also used (w-propanol and isopropanol). In a small number of formulations, ethanol is used in similar proportions to isopropanol. Ethanol is the favoured alcohol in the Scandinavian countries (Norway, Sweden and Finland) where prices of isopropanol and ethanol are comparable. Methanol is used in the USA, where price is the dominant factor. Some changes are taking place as formulations based on isopropanol/ethanol are now comparable in price to the normal 20-30% methanol-based systems. The green benefits of using ethanol from renewable fermentation sources is also causing a small but discernible shift. 

The biomass formed during a fermentation is a source of high-quality protein and vitamins. For this reason Clostridium acetobutylicum was once used to supplement animal feeds (see section 6.2.1.2), and Saccharomyces cerevisiae from the ethanol fermentation now finds a similar use in the United States. Where the value of the fermented biomass has made it attractive as a product in its own right, it is the sheer scale of the process which is important for industrial chemistry. 

X, and Kondo, A. (2013) Reduction of furan derivatives by overexpressing NADH-dependent Adhl improves ethanol fermentation using xylose as sole carbon source with Saccharomyces cerevisiae harboring XR-XDH pathway. Appl. Microbiol Biotechnol, 97, 2597-2607. 

The world demand for lysine is expected to increase continually. The increasing ethanol fermentation capacity for gasohol production provides an opportunity for increased lysine production. Distillers dried grains (DDG), a by-product of ethanol fermentation used as a protein source in animal feeds, is deficient in lysine and other essential amino acids. It needs to be supplemented with lysine for full-value use. 

Ethanol fermentation within lichens under oxygen-deprived conditions has been shown by PTR-MS to emit acetaldehyde and ethanol. The researchers concluded that ethanol fermentation represents both a source of atmospheric VOC emissions and a so far unconsidered carbon loss route for lichens [114]. 

Shen, F., Liu, R., Wang, T., 2009. Effects of temperature, pH, agitation and particles stuffing rate on fermentation of sorghum stalk juice to ethanol. Energy Sources Part A - Recovery Utilization and Environmental Effects 31 (8), 646—656. 

Because oil and gas ate not renewable resources, at some point in time alternative feedstocks will become attractive however, this point appears to be fat in the future. Of the alternatives, only biomass is a renewable resource (see Fuels frombiomass). The only chemical produced from biomass in commercial quantities at the present time is ethanol by fermentation. The cost of ethanol from biomass is not yet competitive with synthetically produced ethanol from ethylene. Ethanol (qv) can be converted into a number of petrochemical derivatives and could become a significant source. 

After 30 hours, the maximum and critical fermentation is underway and the pH must remain above 4.0 for optimal fermentation. However, accompanying bacterial contamination from various sources such as yeast contamination, improper cleaning procedures, slow yeast growth, or excessive temperatures can result in a pH below 4.0. The remaining amylase enzymes, referred to as secondary conversion agents, are inactivated and can no longer convert the dextrins to maltose. Under these circumstances, the fermentor pH continues to drop because of acid production of the bacteria, and the pH can drop to as low as 3.0. The obvious result is a low ethanol yield and quaUty deterioration. 

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