Page 129 - Advances in Textile Biotechnology

110 Advances in textile biotechnology

same period, under various media compositions, no ammonia could be
detected. By means of XPS and dyeing assays with methylene blue (C.I.
Basic Blue 9) and Coomassie brilliant blue (C.I. Acid Blue 90), we con-

cluded that the superficial nitriles of acrylic fibres were converted to the
corresponding amides that were not accessible to amidases. The best results
in terms of increase in colour, measured as K/S for methylene blue, were
obtained at pH 6.5 and in the presence of 0.5% v/v dimethylformamide

(DMF). Owing to the reported enzymatic modifications the acrylic fabrics
became more dyeable with methylene blue (an increase of 15% in K/S),
which is somewhat contradictory to the conclusion that amide groups were
formed and not the acidic groups, on the acrylic surface.
The modification of nitrile surface groups into amide groups was also

accomplished by the action of nitrile hydratases present in cell lysates from
Brevibacterium imperiale and Corynebacterium nitrilophilus (Battistel et al.,
2001). The PAN used in this study was a copolymer containing 10% of vinyl

acetate in two formats, powder and fibre. The enzymatic treatments were
performed in 100 mM phosphate buffer pH 7, at 20 °C for a maximum
period of 48 h, with vigorous shaking (250 rpm). The newly formed amides
were assessed by XPS. After 48 h, for both fi bre and powder forms treated
with the active cell lysate, the content of oxygen increased signifi cantly with
a concomitant decrease in the content of nitrogen. Further hydrolysis into
carboxylic groups was ruled out because of the absence of the XPS peak

characteristic of these groups in the spectrum of the modified PAN polymer.
The oxygen content increased as a function of reaction time, mainly in the

first 2 h, stabilizing after 10 h. This could be explained by the moderately
fast deactivation of the enzyme during the treatment. The decrease in the
contact angle for the modified PAN fibre was verified as well as the ability

of this PAN to react with acid dyes that gave optimal colour yields for
natural fibres such as wool and silk. The untreated controls were inert to

the same dyes. The dye uptake behaviour during treatment correlated with

the increase in the oxygen/carbon ratio of the modified polymer, as expected.

The described enzymatic modification was a promising result for the
improvement of the comfort properties of PAN and the possibility of dyeing
simultaneously mixed yarns of acrylic and wool.
A nitrile hydratase, isolated from the Arthrobacter sp. ECU1101, was
used to selectively transform the nitrile into amide groups of acrylic fi bres
comprising 85% of acrylonitrile and 10% of methylacrylate (Wang et al.,
2004). The enzymatic treatments were performed in 50 mM phosphate
buffer pH 7, at 30 °C for a period of 48 h, with vigorous shaking (200 rpm).
The addition to the media of 0.1% w/v of JFC (a non-ionic surfactant with
fatty alcohol polyoxyethelene ether as the main ingredient) and 0.1% of
DMF showed that the use of the non-ionic surfactant improved the enzyme

activity whereas DMF did not (Tables 5.1–5.3). The modified acrylic fi bre

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