Biopolymer, fermentation

Biopolymer Extraction. Research interests involving new techniques for separation of biochemicals from fermentation broth and cell culture media have increased as biotechnology has grown. Most separation methods are limited to small-scale appHcations but recendy solvent extraction has been studied as a potential technique for continuous and large-scale production and the use of two-phase aqueous systems has received increasing attention (259). A range of enzymes have favorable partition properties in a system based on a PGE—dextran—salt solution (97) ... 

Xanthan gum [11138-66-2] is an anionic heteropolysaccharide produced by several species of bacteria in the genus Aanthomonas A. campestris NRRL B-1459 produces the biopolymer with the most desirable physical properties and is used for commercial production of xanthan gum (see Gums). This strain was identified in the 1950s as part of a program to develop microbial polysaccharides derived from fermentations utilizing com sugar (333,334). The primary... 

Fermentation of Sweet Sorghum into Added Value Biopolymer of Polyhydroxyalkanoates (PHAs)... 

Norton, C.J., Falk, D.O., and Luetze l Schwab, U.E. "Xanthan Biopolymer Semi-Pi lot Fermentation," SPE paper 8420, 1979 SPE Annual Technical Conference and Exhibition, Las Vegas, Septemeber 23 26. 

The successful use of crop plants as a production method for biopolymer not only depends on the amount of PHA accumulated in plants but also on the type and quality of the PHA synthesized. Since poly(3HB) is a polymer with poor physical characteristics [16], it was important to engineer plants for the synthesis of PHA co-polymers with better physical characteristics. Poly(3-hydroxybu-tyrate-co-3-hydroxyvalerate) [poly(3HB-co-3HV)] is the best studied co-poly-mer. Poly(3HB-co-3HV) has lower crystallinity, and is more flexible and less brittle than poly(3HB) homopolymer [16]. Synthesis of poly(3HB-co-3HV) in bacteria was first achieved by fermentation of R. eutropha on glucose and propionic acid [2]. For a number of years, production of poly(3HB-co-3HV),... 

As discussed in previous sections, sugars, starch and (ligno)cellulose can be converted into ethanol by fermentation, the latter via preliminary chemical and physical pretreatment followed by enzymatic breakdown of the biopolymers. Pure ethanol can be added to gasoline or diesel. However, this requires an energy-intensive distillation step. This and the energy used in fertilizers, transportation... 

Different routes for converting biomass into chemicals are possible. Fermentation of starches or sugars yields ethanol, which can be converted into ethylene. Other chemicals that can be produced from ethanol are acetaldehyde and butadiene. Other fermentation routes yield acetone/butanol (e.g., in South Africa). Submerged aerobic fermentation leads to citric acid, gluconic acid and special polysaccharides, giving access to new biopolymers such as polyester from poly-lactic acid, or polyester with a bio-based polyol and fossil acid, e.g., biopolymers . 

Consumer acceptance is not a big issue yet, but is one to keep an eye on. Supermarket chains in the UK have refused a biopolymer because it was derived from genetically modified plants, despite the fact that it is an eco-friendly material. There is even a discussion as to whether vitamins produced by fermentation... 

The melting temperature (Tm) of the biopolymer was determined from differential scanning calorimetry thermograms. The Tm value of the P (3HB) homopolymer was about 177°C and P (3HB) with 10% P(3HV) was about 150°C (Table l),but the Tm values of biopolymer extracted from E. coli HMS174 were about 166°C. The Tm of the sample was lower than that of the P (3HB) homopolymer, but higher than that of the P (3HB) with 10% P (3HV), because the P (3HV) content in the sample is only about 4.5% of the biopolymer produced. The PHV content in extracted biopolymer was low, the flexibility of extracted biopolymer was low, and different fermentation conditions should be investigated. 

Fig. 6. H NMR spectrum of biopolymer produced by E. coli HMS174 with plasmid pUC19/PHA in fermentation.

The biopolymer extracted from the fermented broth was purified through successive washings with 70, 80, and 90% (v/v) ethanol P.A., respectively. The biopolymer was dried by introducing nitrogen gas under controlled heating. 

As described, production of the biopolymer was accompanied by the determination of the viscosity of the fermented broth. Viscosity measurements under different conditions described in the experimental design were done as a function of shear rate. In order to obtain suitable conditions that... 

In February 2006, Japan s Mitsubishi Motors announced that it is to use the biopolymer, polybutylene succinate (PBS), in the interior of its new mini-car launched next year. In conjunction with Aichi Industrial Technology Institute, it has developed a material that uses PBS combined with bamboo fibre. PBS is composed of succinic acid, which is derived from fermented corn or cane sugar, and 1,4-butanediol. Bamboo grows quickly and is seen by Mitsubishi as a sustainable resource. In lifecycle tests, the PBS-bamboo fibre composite achieves a 50% cut in carbon dioxide emissions compared with polypropylene. Volatile organic compound levels are also drastically reduced, by roughly 85%, over processed wood hardboards. 

Examples of biotech-based processes and products that are already to be found are biocatalysis and biomolecules in fine chemicals, biopolymers as substitutes for synthetic polymers, enzymes and modified additives in specialties, and modern fermentation as a production process for basic and intermediate organics. The market for biotech-based products (excluding traditional fermentation in, for ex-... 

We estimate that biotechnology will be competing with approximately 30 percent of the total chemical market by 2010 on the basis of lower cost and/or superior product features. Approximately 10 to 20 percent of basic and intermediate chemicals could be affected by production through modern fermentation. Specialties will be replaced by enzymes and natural flavors, pigments and additives. Polymers will face competition from biopolymers that are competitive in price with both polyester and nylon. 

The butyrate or octanoate copolymer and butyrate or hexanoate or decanoate terpolymer have properties similar to those of higher-grade LLDPE (linear low-density polyethylene) and higher-grade PET (polyethylene terephthalate). They can be molded or converted into films, fibers, and nonwoven fabrics. The biopolymer is produced by low-cost fermentation or from wastestream substrates. 

Most biopolymers are produced as extracellular metabolites by fermentation in bioreactors leading to special technical problems caused by the very viscous solutions that make mass transfer and mixing in the fermentation fluids difficult. Large volumes of water and solvents are needed for dilution and extraction, respectively. 

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