Cellulose fermentation substrate

More recently, interest has developed in the use of enzymes to catalyze the hydrolysis of cellulose to glucose (25—27). Domestic or forest product wastes can be used to produce the fermentation substrate. Whereas there has been much research on alcohol fermentation, whether from cereal grains, molasses, or wood hydrolysis, the commercial practice of this technology is primarily for the industrial alcohol and beverage alcohol industries. About 100 plants have been built for fuel ethanol from com, but only a few continue to operate (28). 

Figure 2. Cellulose synthesis by Rut-NG14 in a 6% cellulose fermentation. (Data from M. Mandels, U.S. Army Laboratories, Natick, Mass.) (O—O) Residual dry weight, (A—A) FP units/mh (42), ( — ) soluble protein, (A—A) mycelial protein. Substrate 6% two-roll milled cotton Mandels (42) basic salts medium without urea inoculum 20% v/v of a 3-day-old shake flask mycelium pH > 3, continuous addition of NH OH.

Dry citrus peels are rich in pectin, cellulose, and hemicellulose and may be used as a fermentation substrate. Production of multienzyme preparations containing pectinolytic, cellulolytic, and xylanolytic enzymes by the mesophilic fungi A. niger BTL, Fusarium oxysporum F3, Neurospora crassa DSM 1129, and Penicillium decumbens under SSF on dry orange peels was enhanced by optimization of initial pFI of the culture medium and initial moisture level (Mamma et al., 2008). Under optimal conditions A. niger... 

Ethanol production uses a large number of substrates such as sugar cane, cassava, grain, straw, and cellulose in yeast fermentation. In addition to yeast, other organisms capable of utilizing cellulose and starch, for example, are used. Enzymes are used to convert feedstock to a fermentable substrate. 

It is estimated that some 10 tons of carbohydrate polymers, mostly cellulose, are produced annually i.e., 25 tons per person on earth. Fortunately, carbohydrate-rich materials including urban refuse, agricultural residues and lignocellulosics are good fermentation substrates, hence microorganisms assure that biosynthesis and decay are in balance. That a major product of nature s biomass transformation should be a high molecular weight linear polyester is perhaps unexpected. 

Clostridia have the ability to use many different carbon sources like pentoses and hexoses, but also polysaccharides like starch (Jones and Woods 1986 Ezeji et al. 2007a). This ability is important for the use of low-cost cellulosic waste materials from agriculmre as fermentation substrates, since substrate cost is one of... 

Grain that is usable as food or feed is an expensive substrate for this fermentation process. A cheaper substrate might be some source of cellulose such as wood or agricultural waste. This, however, requires hydrolysis of cellulose to yield glucose. Such a process was used in Germany during World War II to produce yeast as a protein substitute. Another process for the hydrolysis of wood, developed by the U.S. Forest Products Laboratory, Madison, Wisconsin, uses mineral acid as a catalyst. This hydrolysis industry is very large in the former Soviet Union but it is not commercial elsewhere. 

Processes have been developed in North America to pilot scale growing the bacterium Cellulomonas or the fungus Trichoderma on pre-treated milled cellulosic material in conventional fermentors, ie in a liquid medium. However, preparation costs are considerably higher than with solid-substrate fermentations. 

Only this fungus amongst those listed is capable of using the cellulose of which paper is composed. Solid substrate fermentation would be foe easiest and cheapest production system. 

The nature of the diet sets the basic pattern of metabohsm. There is a need to process the products of digestion of dietary carbohydrate, lipid, and protein. These are mainly glucose, fatty acids and glycerol, and amino acids, respectively. In ruminants (and to a lesser extent in other herbivores), dietary cellulose is fermented by symbiotic microorganisms to short-chain fatty acids (acetic, propionic, butyric), and metabohsm in these animals is adapted to use these fatty acids as major substrates. All the products of digestion are metabohzed to a common product, acetyl-CoA, which is then oxidized by the citric acid cycle (Figure 15-1). 

Over the past two decades, considerable interest has been directed toward the conversion of cellulosic biomass (such materials as wood wastes, bagasse, and straw) into useful products, notably fuels. Several procedures, including fermentation, gasification, liquefaction, and pyrolysis, have been commercially applied to carbohydrates with various degrees of success. In order to use the polysaccharides present in lignocel-lulosic materials as a substrate in fermentation processes, pretreatments are necessary, such as with steam (under slightly acid conditions) or... 

Pretreatment of Substrate. Several different lignocelluloses were pretreated with NaOH. This pretreatment partially solubilizes the hemicelluloses and lignin and swells the cellulose so that the organism can utilize it for its growth and for production of a cellulase system in SSF. The treated lignocelluloses were not washed. The NaOH treatment is done with a minimum amount of water so that, after the addition of nutrient solution and inoculum, the moisture content is less than 80% wt/wt and there is no free water in the medium. More water was added to make suspensions of different lignocellulosic substrates of the desired concentration (1% or 5%) for liquid-state (submerged) fermentation (LSF). 

When wheat straw was fermented in LSF, the FP cellulase level reached 6 lU/ml (300 lU/g cellulose or 120 lU/g substrate) (Table I) by day 11, decreasing thereafter. This showed that SSF was better than LSF for cellulase production when using wheat straw. 

A maximum FP cellulase of 6.3 lU/ml (191 lU/g cellulose or 126 lU/g substrate) was obtained on NaOH-treated CTMP after 20 days in SSF. On untreated CTMP, the FP cellulase remained about 5 lU/ml from 20 to 26 days of fermentation and then increased to 7.2 at 30 days of fermentation (Table III). This indicated that CTMP was a good substrate for cellulase production in SSF even without the mild NaOH treatment. 

Fermentation time (days) FP cellulase (lU/ml) FP cellulase (lU/g cellulose) FP cellulase (lU/g substrate)... 

Substrate and Pretreatment. Sweet corn (hybrid Lingodor) of W.H. Perron Laval, Quebec was grown in well prepared soil in a plot of 3 x 2 meters. Corn stalks were ground to 20 mesh to be used as a substrate. It was pretreated with 1.5% sodium hydroxide (NaOH) wt/vol with substraterwater ratio of 1 10 at 121 C for 60 minutes. The substrate was not washed after the pretreatment, and all the solubilized polymers (hemicelluloses and lignin) were retained along with the insoluble polymer (cellulose) in the fermentation medium. The composition of corn stalk is presented in Table 1. 

Another factor rarely considered is the zone of the root system subjected to the microbial metabolite. It is likely that the metabolites will only be formed in particular regions of the soil where there are suitable substrates for producer micro-organisms and it is unlikely that the entire root system will come under the influence of a metabolite. For example, acetic acid is a coinnon microbial fermentation product of cellulose and is phytotoxic ( 5,... 

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