Renewable carbohydrates

Hydroxymethylfurfural (HMF) can be readily obtained from acid-catalysed dehydration of carbohydrates. On the other hand, FFA can be further reacted to produce 2,5-furandiacetic acid and 5-carboxyfuran-2-acetic acid which could form polymers, much like tereftahc acid. Therefore the carbonylation of MF can be regarded as the first step of the green manufacture of polymers on the basis of renewable (carbohydrate) raw materials. 

The present utilization of carbohydrates as a feedstock for the chemical industry is modest, when considering their ready availability, low cost and huge potential [92], The bulk of the annually renewable carbohydrate biomass consists of polysaccharides, but their non-food utilization is still modest. The low-molecular-weight carbohydrates, that is, the constituent units of these polysaccharides, are potential raw materials for several commodity chemicals in fact, glucose (available from cornstarch, bagasse, molasses, wood), fructose (inulin), xylose (hemicelluloses) or the disaccharide sucrose (world production 140 Mtons year-1) are inexpensive and available on a scale of several ten thousands. 

Fermentation-derived organic acids and their esters are potentially important chemical feedstocks for polymers and specialty polymers, but most significantly as alternative solvents for industrial and consumer applications. For example, lactate esters are derived from renewable carbohydrate raw materials such as cornstarch. They exhibit much lower toxicity compared with halogenated hydrocarbons and ethylene glycol ethers and are environmentally benign. Some studies suggested that lactate ester solvents have the potential of replacing petroleum-based solvents... 

Ethyl lactate is a nontoxic and biodegradable solvent derived from renewable carbohydrates. Its use and acceptance can be increased only if it is competitively priced to replace traditional organic solvents such as methylene chloride and chloroform. Argoime s National Lab developed a selective membrane technology for synthesizing ethyl lactate that eliminates the production of an equimolar amount of salt waste. The process uses pervaporation membranes and catalysts to directly convert the salts to esters, thereby eliminating the problem of salt waste. This approach reduces the product cost by half. The concept of pervaporation consists of the use of a membrane that selectively accepts one compound from a mixture of compounds it is explained in Chapter 6. 

ANL s novel process uses pervaporation membranes and catalysts. In the process, ammonium lactate is thermally and catalytically cracked to produce the acid, which with the addition of alcohol is converted to the ester. The selective membranes pass the ammonia and water with high efficiency while retaining the alcohol, acid, and ester. The ammonia is recovered and reused in the fermentation to make ammonium lactate, eliminating the formation of waste salt. The innovation overcomes major technical hurdles that had made current production processes for lactate esters technically and economically noncompetitive. The iimovation will enable the replacement of toxic solvents widely used by industry and consumers, expand the use of renewable carbohydrate feedstocks, and reduce pollution and emissions. 

Natural feedstocks must serve many human purposes. Select carbohydrates as raw materials are valuable due to their actual or potential nutritional value. For example, already operating are protein plants utilizing rapidly reproducible bacteria which metabolize cellulose wastes. Thus, bacteria are added to a nutrient broth emphasizing cellulose the bacteria feed on the mixture, converting it to more protein rich bacteria the bacteria are harvested and used as a protein feed meal. However, there is potentially available enough renewable carbohydrates to serve both the food and the polymer needs, and research into the modification of carbohydrates must continue at a heightened pitch. 

Within the framework of a research project together with Dutch based paint producer SigmaKalon, the development of alkyd resins with low intrinsic viscosity was aimed for. In order to achieve this, we explored the potential of two types of renewable, carbohydrate derived resources as the polyhydric alcohol part of alkyd resins, i.e. sucrose and inulin. " These carbohydrate based resources were chosen because of various reasons ... 

In this communication we extend our prior observations and demonstrate the use of xylan-rich, hemicellulosic residual fractions of wood for the production of P(3HB-co-3HV) by B. cepacia. Levulinic acid, the secondary carbon source utilized in this bioconversion process, can be produced cost-effectively from a vast array of renewable carbohydrate-rich resources including cellulose-containing forest and agricultural waste residues 24,25). This five-carbon cosubstrate (4-ketovaleric acid) serves as a precursor to the 3-hydroxyvalerate (3HV) component of the B. cepacia-dtnved P(3HB-co-3HV) copolymer (Figure 1). Further, the mol % 3HV composition and associated physical/mechanical properties of the copolymer can be manipulated as a function of the substrate concentrations provided in the fermentation. Physical-chemical characterizations of such PHA copolymers are reported herein, as evidence supporting the potential of these biodegradable thermoplastics to serve as viable replacements for conventional, environmentally recalcitrant commodity plastics. 

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