Via Sugar Fermentation

1 Microorganisms and Metabolic Pathway A number of microorganisms are able to accumulate 2,3-BD but only a few do so in what might be considered significant quantities. Species which are noted for this ability include those belonging to the genera of Klebsiella, Enterobacter, Paenibacillus, Bacillus, and Serratia, which are considered to be of industrial importance in the production of 2,3-BD (Maddox, 1996). 

A variety of monosaccharides (hexoses or pentoses) can be fermented to produce 2,3-BD (Syu, 2001). In bacterial metabolism, monosaccharides must first be converted to pyruvate before generation of major products. From glucose, pyruvate is formed in a relatively simple manner via the Embden-Meyerhof pathway (glycolysis). In contrast, the production of pyruvate from pentoses must proceed via a combination of the pentose phosphate and Embden-Meyerhof pathways (Jansen and Tsao, 1983). In addition to 2,3-BD, the pyruvate produced from the monosaccharides is then channeled into a mixture of acetate, lactate, formate, succinate, acetoin, and ethanol, through the mixed acid-2,3-BD fermentation pathway (Ji et al., 2011a). 

TABLE 10.1 2,3-Butanediol Stereoisomers Produced by Different Microorganisms 

TABLE 10.2 Microbial 2 -Butanediol Production Using Different Bacterial Species 

Microorganism Substrate Method Diol concentration (g/L) 2,3-Butanediol Acetoin Diol productivity (g/L.h Diol yield (g/g) Reference 

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Propionibacterium species are used to produce propionic acid via sugar fermentation. As it has wide antimicrobial activity, propionic acid is used in cosmetic formulation as preservatives. Improved production of hydroxy acids from simple sugars can be achieved by using engineered microorganisms developed by recombinant DNA technology. 

Rodriguez, B.A., Stowers, C.C., Pham, V., Cox, B.M., 2013. The production of propionic acid, propanol and propylene via sugar fermentation an industrial perspective on the progress, technical challenges and further outlook. Green Chemistry, http / / dx.doi.org/10.1039 / c3gc42000k. 

Table 13.2. Types ol Sugar Fermentations in Which Pyruvate is Produced via the Embden-Meyerhol Pathway.

Lactic acid is supplied commercially as an odourless and colourless viscous liquid. It is produced via the fermentation, using lactic acid bacteria, of carbo-hydrates such as com, potato or rice starch, cane or beet sugar, or beet molasses. 

Lactic acid (LA) is one of the top carbohydrate-derived chemicals and it was recently included in BozeU and Petersen s revised selecticai of the top ten sugar-based chemicals [10, 24]. The conversion of carbohydrates into LA via anaerobic fermentation has been known for ages [25]. The first industrial fermentation was developed by A. Boehringer in 1895 and at the present time the global installed production capacity is estimated at 0.5 Mton year [10, 26, 27]. The current fermentation process and its issues will be critically discussed in Sect. 3 in light of the major application of LA today, i.e., as monomer for commercial bioplastic PLA [28]. Besides being used for polyester synthesis, LA is seriously considered as a platform chemical for the synthesis of a diverse range of chemicals such as pyruvic acid, 2,3-pentanedione, and acrylic acid [10, 29]. 

A great example of companies making the transition to sugar as a source for chemicals may be found in companies Hke BioAmber [52] and Myriant [53]. These companies have identified succinic acid, one of the compounds identified in Fig. 1.3 as a market opportunity. Succinic acid is a 4-carbon chain molecule that is more cost effectively obtained via a sugar fermentation process than it is obtained from petrochemical sources. Additionally, succinic acid is a useful building block for a variety of commodities (e.g., 1,4-butanediol) and specialty chemical end use applications. So market demand for it is assured. Sadly there are currently not many other success stories like these. 

Ethanoi found in aicoholic beverages is generally produced via the fermentation of sugars by yeast. However, there are many other important industriai uses for ethanol (as a gasoline additive, as a solvent, for perfumes and paints, etc.), and therefore, an aiternative, more efficient process for producing pure ethanol is required. This can be accomplished by the acid-catalyzed hydration of ethyiene obtained from petroleum ... 

Xylose is the main carbohydrate present in the hemicellulose fraction (second most abundant component of lignocellulose, representing about 80 % of total sugars) (Girio et al. 2010). Potentially, the released carbohydrates, mono- and dimeric sugars, are substrates for the production of value-added products such as ethanol, xylitol, n-butanol, 2,3-butanediol, and lactic acid via microbial fermentation processes (Chandel et al. 2010, 2011, 2012). 

U.S. production of etylene was 29.2 billion pounds in 1979. It would take the equivalent of 3 billion bushels of corn to produce the same quantity of ethylene via ethanol fermentation and subsequent dehydration. The use of other substrates, such as wheat, sugar cane, sweet sorghum, whey, waste paper, and fast-growing trees, has to be explored. 

Yeast (qv) metabolize maltose and glucose sugars via the Embden-Meyerhof pathway to pymvate, and via acetaldehyde to ethanol. AH distiUers yeast strains can be expected to produce 6% (v/v) ethanol from a mash containing 11% (w/v) starch. Ethanol concentration up to 18% can be tolerated by some yeasts. Secondary products (congeners) arise during fermentation and are retained in the distiUation of whiskey. These include aldehydes, esters, and higher alcohols (fusel oHs). NaturaHy occurring lactic acid bacteria may simultaneously ferment within the mash and contribute to the whiskey flavor profile. 

The reliance of fossil fuels has been challenged by lower cost and renewable sources that are more environmentally friendly. The traditional chemical plant has met serious competition from green plants. Many monomers are now made via fermentation, using low-cost sugars as feedstock. Some of the commodity monomers are under siege by chemicals extracted from biomass. Monomer production has been expanded to include many more monomers from nature. 

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