Page 190 - Advances in Textile Biotechnology

8

Enzymatic treatment of wool and silk fi bres

J. SHEN, De Montfort University, UK

Abstract: In this chapter, the major enzymes used as bio-catalysts for
protein fibre processes in the textile industry are described and the

protein structure of wool and silk fibres is explained. Recent

developments are presented in the application of enzymes in wool

scouring and finishing processes to achieve a variety of fi nishing effects
including softness, reduction of prickle and shrink-resistance. Recent
developments in the application of enzymes in silk degumming and

finishing are also reviewed.
Key words: enzymes, proteases, wool, bioscouring, textile fi nishing,
shrink-resistance, silk fibroin and sericin, silk degumming.

8.1 Introduction

There is increasing demand for natural textile goods by consumers. Wool
and silk are the major protein-based natural fibres. They are well recognised

as luxury textile fibres for use in clothing, upholstery, rugs and bedding

materials including wool or silk filled duvets. The world’s wool retail sale

per annum is about $80 billion with more than 2.1 million tonnes of greasy
wool produced every year (IWTO Roadmap, 2009). Silk is produced in
smaller quantities: about 130 000 tonnes per year, but silk has remained as

a speciality fibre for use in high value textiles. Interest in the environment
and consumer demands will certainly increase the use of these natural
fi bres.
Natural wool fibre processing involves extensive wet treatments to

improve the function and properties of fibres and fabrics including softness,
reduction of pilling and dimensional stability. These treatments bring about
some environmental problems such as increasing the chemical oxygen
demand (COD) of wastewater from wool scouring, the presence of absorb-
able organic halides (AOX) in the case of shrink-resist finishing of wool

and the use of heavy metals to obtain certain colour fastness. The textile
industries are being asked to lessen the environmental impact of textile wet
processes, especially restricting AOX in effl uent, which has become part of
the legislation in EU countries. Owing to such environmental concerns,
much research effort has gone into searching for environmentally friendly

methods for wool processing. The environmental benefits gained by using
enzymes as biocatalysts in wool processes to replace harsh chemicals,
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