Page 255 - Advances in Textile Biotechnology

236 Advances in textile biotechnology

polypeptide-based materials, and the maturation of recombinant DNA
technologies, which allows these materials to be synthesized in large yields
with precise control over the chain-length, stereochemistry and monodis-
persity (Chow et al., 2008). Protein polymers with amino-acid sequences
based on the consensus repeat sequences of silk, collagen, elastin glutenin,

and resilin have been a primary focus in the design of fibrous protein based
polymeric materials (Kiick, 2007).

10.2 Principles of recombinant DNA methods applied
in the production of recombinant proteins

The ability to manipulate genes and their products by recombinant DNA
technology in microbial, animal and plant systems has signaled a number

of new possibilities for the production of modified or new fi brous biopoly-

mers or protein-based polymer as well as modified or new enzymes with
better properties (more temperature stability, increased activity and
improved performance) by ‘splicing’ relevant enzymatic genes into another
organism which has improved pre-existing treatments such as many enzy-
matic transformation processes of textile processing and after care. Indeed,
biotechnological approaches offer the opportunity of replacing existing
chemical or mechanical processes for a cleaner production technology than
conventional procedures which cause severe pollution problems from
textile effl uents (Chen et al., 2007, Rogers, 2000).
The control of biosynthetic methods for specifying polymer sequence,
molecular weight and consequently structure, arises from the high fi delity
4
(error rates less than one in 10 ) with which a gene encoding a target protein
is converted to its corresponding protein sequence at the ribosome. The two

general steps by which this conversion occurs are: first, a specifi ed DNA
sequence is copied into a corresponding mRNA sequence (transcription),
and second, these mRNA fragments are used as templates to direct the
synthesis of proteins (translation). In the translation of the mRNA template
into a protein, transfer RNA (tRNA), which acts as an adaptator between
the mRNA and the amino-acids of the proteins, and the enzymes amino-
acyl-tRNA synthetases, which control the attachment of amino acids to
their cognates tRNAs, are involved. Because there are multiple approaches
for assembling target genes, this strategy has allowed the synthesis of many
types of protein polymers and block co-polymers (Kiick, 2007, Sankarana-
rayanan and Moras, 2001).
Frequently, discrete domains of proteins support a certain structural,
biochemical or biological activity and thus it is often not necessary to
express the full-length protein to address a particular biological question
(Hallberg, 2008). Known fibrous proteins such as silks, elastin and collagens

are characterized by a highly repetitive primary sequence (mainly com-
posed of tandem of repeated blocks of amino-acids sequences), which leads

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