Chemical starch-producing feedstocks

PLA is finding a wide range of uses, both as a moulded product for the packaging sector, as a film for wrapping and lamination applications, as a fibre fill (pillows/duvets etc.), as a foam, and as a spun textile fibre. Lactic acid produced from microbial fermentation of starch also has many other industrial opportunities, as it is a useful base chemical feedstock for a range of applications. Lactic acid can be chemically converted to propylene glycol, the base for a range of... 

Com-derived starch is a readily available feedstock in the U.S. It is produced efficiently in large quantities in com wet mills and provides the basis for much of the biomass-derived chemical production presently in the market The starch is enzymatically hydrolyzed on a large s e to produce glucose, much of which is isomerized to fhictose for use as food sweetener, and the rest mostly goes into ethanol production for automotive fuel. The several separation processing steps in the com wet mill are summarized in Figure I. Equivalent processing could be lied to wheat and potato or other starch when the feedstock is available at a suitably low price. 

L-lactic acid has long been used as a food additive and has recently received great attention because it can be used as an important feedstock for the production of other chemicals such as polylactic acid (PLA), acetaldehyde, polypropylene glycol, acrylic acid, and penta-dione. Among them, PLA is the most important product as it can be used to manufacture thermo-formed containers, packaging, nonwovens, paper-coated articles, and film products. Lactic acid can be produced from sucrose, whey (lactose), and maltose or dextrose from hydrolyzed starch using Lactobacillus strains. 

Agricultural crops. These feedstocks include the currently available commodity products such as cornstarch and corn oil, soybean oil and meal, wheat starch, other vegetable oils, and any newly developed component of future commodity crops. They generally yield sugars, oils, and extractives, although they also can be used to produce plastics and other chemicals and products. 

Polymers derived from renewable resources (biopolymers) are broadly classified according to the method of production (1) Polymers directly extracted/ removed from natural materials (mainly plants) (e.g. polysaccharides such as starch and cellulose and proteins such as casein and wheat gluten), (2) polymers produced by "classical" chemical synthesis from renewable bio-derived monomers [e.g. poly(lactic acid), poly(glycolic acid) and their biopolyesters polymerized from lactic/glycolic acid monomers, which are produced by fermentation of carbohydrate feedstock] and (3) polymers produced by microorganisms or genetically transformed bacteria [e.g. the polyhydroxyalkanoates, mainly poly(hydroxybutyrates) and copolymers of hydroxybutyrate (HB) and hydroxyvalerate (HV)] [4]. 

Carbohydrates are the most abundant resource for the conversion of renewable feedstocks in useful chemicals and energy. Approximately 180 billion tons of biomass is produced from photosynthesis each year, including about 180 million tons of edible sugars [1] and more than 1 billion tons of starch from grains [2]. 

In addition to their fibrous tissues, some species also produce sugar and starch in sufficient quantities to warrant extraction and conversion to ethanol. The latter can displace petroleum in the production of motor fuel or chemical feedstocks (IQ-IS). Other species store additional energy in the form of natural hydrocarbons. 

At present succinic acid is a specialty chemical with an annual production volume of about 30 000 tons worldwide. Fossil-based succinic acid is most commonly prepared via hydrogenation of maleic anhydride (by oxidation of n-butane or benzene) [73]. In the field of bio-based chemicals and building blocks succinic acid is considered to be one of the most important platform chemicals [1, 74, 75], and as a result of the introduction of biosuccinic acid the production volume is expected to double or triple within years. Several fermentation processes have been described to produce bio-based succinic acid. Common feedstocks for these processes include glucose, starch and xylose [76]. The commercial potential for bio-succinic acid is illustrated by the numerous initiatives by companies that are working towards, or already... 

Despite the efficiency of the manufacture of ethanol from petrochemical feedstocks, much of the world s production is based on a fermentation process. Over the past 75 years in the United States, where the total annual production now stands at just under 4 million tonnes, the source of this basic chemical feedstock has swung away from fermentation to petrochemistry and back again (Table 6.1). The carbon source for the fermentation is glucose derived from starch (see Section 6.6). An even larger quantity, about 9.5 million tonnes, is produced each year in Brazil from cane sugar. Nowadays the prime consumer is the motor car. 

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