Starch biopolymer products

The use of waste materials as feedstocks for PHA biosynthesis constitutes a viable strategy for cost-efficient biopolymer production and supports various agro-industrial branches to overcome existing waste disposal problems. The subsequent Table 7.2 provides a compilation of selected carbon-rich waste streams that are reported to be potential feedstocks for microbial PHA production. Such carbon substrates that are of importance for human nutrition, like pure starch or edible oils from olives, soya or palm trees, are not included in this compilation. 

Starch biopolymers may be utUized in the packaging industry not only as protective wrappings for products stored under ambient conditions, but also at low temperatures and for frozen products. In connection with the possible applications of starch biopolymers as, for example, ice-cream sticks or stiff packaging for frozen food, selected mechanical features of starch moldings have been tested after storage under varied temperature conditions [1-4, 9, 10, 12]. 

Binding enzymes to solid supports can be achieved via covalent bonds, ionic interactions, or physical adsorption, although the last two options are prone to leaching. Enzymes are easily bound to several types of synthetic polymers, such as acrylic resins, as well as biopolymers, e.g., starch, cellulose [52], or chitosan [53,54]. Degussa s Eupergit resins, for example, are used as enzyme carriers in the production of semisynthetic antibiotics and chiral pharmaceuticals [55], Typically, these copolymers contain an acrylamide/methacrylate backbone, with epoxide side groups... 

The following sections focus on the description of the state and phase transition behavior of starch systems, as schematically illustrated in Figure 8.5, with an emphasis on their molecular organization and their response to various environments (temperature, solvent, other co-solutes, etc.). Selected material properties are also discussed in an effort to demonstrate structure-function relationships of this biopolymer mixture in pure systems and in real food products. 

Fig. 33.1. Starch a biopolymer of glucose molecules used today in the United States as the basis for production of fuel ethanol from corn grain.

The major classes of biopolymer, starch and starch blends, polylactic acid (PLA) and aliphatic-aromatic co-polyesters, are now being used in a wide variety of niche applications, particularly for manufacture of rigid and flexible packaging, bags and sacks and foodservice products. However, market volumes for biopolymers remain extremely low compared with standard petrochemical-based plastics. For example, biopolymer consumption accounted for just 0.14% of total thermoplastics consumption in Western Europe for 2005. 

The price of starch-based biopolymers has come down considerably over the last three years as production volumes have increased, more efficient production processes have been deployed and lower cost raw materials have been found. In 2003, the average price of starch blends was around 3.0-5.0 per kg. In 2005, the average price range of starch blends was down to 1.5-3.5 per kg, with an average price close to 1.75 per kg. 

Starch-based biodegradable polymers also have a better environmental image than synthetic biopolymers as they are based on sustainable resources, which open up marketing opportunities for brand owners who wish to promote their products as being packaged in materials based on sustainable resources. 

Biopolymer Technologies (Biop) offers a starch-based material containing an additive consisting of a vinyl alcohol/vinyl acetate copolymer. In 2005, the company transferred production of its bioplastics from The Netherlands to Schwarzheide in Germany and invested 7m in a new plant there, increasing its production capacity to 10,000 tonnes per annum. The announcement followed the decision earlier in 2005 by BASF to produce its Ecoflex biodegradable plastic, one of the components of Biop s Biopar resins, at the Schwarzheide site. 

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