Publication
Modification of cellulosic fibres using oxidoreductases
| Summary: | Laccases catalyse the oxidation of various phenolic compounds resulting in the formation of dark brown and high molecular weight compounds. The process of laccase reaction with phenolic products generates the previous formation of o-quinones that are high reactive and able to polymerise, forming coloured high molecular weight compounds. This potentiality of laccase is subject of many researches leading to an increase of interest in new bio-polymers production, namely “environmentally friendly” processes. Enzyme catalysing processes are performed under milder condition requiring less chemical consumption than chemical processes. The coloured polymers enzymatically produced have been studied to introduce in the textile and cosmetic fields by means of colour coatings on fibres and hair. The main objective of this work is the surface modification of cellulosic fibres by means of polymer coating. The polymer production catalysed by laccase was studied using various phenolic substrates. The first attempt to produce suitable polymers was performed with catechol which was easily oxidised by laccase and showed dark colour appearence. In order to attach the polymers “in situ” onto cotton fabrics surface, the functionalisation was preceded. The aminisation was made with a reactive dye forming aromatic amine groups at the cellulose surface, therefore providing a higher ability for polymers coupling. Cotton fabrics coated with the new polymers presented a dark visible colour and high resistance to hydrolysis by cellulase. Non-toxic and non-harmful phenolic substrates such as flavonoids (rutin, morin and quercetin) were further introduced in the laccase reaction medium as potential products for lignocellulosic fabrics colouration. The optimum conditions for polymer production and colouration of fabrics were studied considering several reaction parameters. The level of mechanical agitation and incubation temperature were the decisive factors of colour absorption on fibres. Besides the incubation conditions, the interaction between flavonoids in the reaction medium and the natural flavonoids existing on fibres was also a positive factor proved by higher colour strength and colour resistance through scoured fabrics. Among the used flavonoids, rutin presented the lower polymerisation rate and poor affinity to the fabrics. When the two steps method was used, the polymers were intensively absorbed at high temperature (90°C) due to the enhancement of molecular vibrations both in fibres and in the components of flavonoid solution. The polymers synthesised from flavonoids applied to cotton fabrics showing a good washing fastness (4-5) when incubated at high temperature (90°C) and an excellent friction fastness (5) in all the reaction conditions used. Nevertheless, the weathering fastness was very poor (60% of colour vanishing after 64 hours of light exposure). The elimination of the bleaching step was positively proposed from the conventional textile processes leading to a decrease of pollutant effluents and cost saving. Finally, lignosulfonates were studied as phenolic substrates of laccase. Dynamic instrumental techniques were used to monitor the laccase functions on reaction medium and the physical and chemical substrate changes. The double function of laccase catalysis i.e. polymerisation and depolymerisation was confirmed by Zeta potential and UV-Vis spectrum analysis. The molecular weight increase caused by laccase polymerisation was confirmed by SEC/GPC analysis (MW increased 1700 Da). FT-IR analysis were also performed in order to monitor the structural changes occurred by enzymatic polymerisation. The colouration of flax fabrics with polymerised lignosulfonates was also carried out. The samples coloured with the new compounds, polymerised for 7 days, presented an increase of colour uptake, measured in terms of K/S. The obtained results propose a new concept of bio-polymer production and their practical application on lignocellulosic fibres modification. However, colour fastness is still a limitary factor to take into account on further industrial applications. |
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| Main Authors: | Kim, Suyeon |
| Year: | 2009 |
| Country: | Portugal |
| Document type: | doctoral thesis |
| Access type: | restricted access |
| Associated institution: | Universidade do Minho |
| Language: | English |
| Origin: | RepositóriUM - Universidade do Minho |
| Summary: | Laccases catalyse the oxidation of various phenolic compounds resulting in the formation of dark brown and high molecular weight compounds. The process of laccase reaction with phenolic products generates the previous formation of o-quinones that are high reactive and able to polymerise, forming coloured high molecular weight compounds. This potentiality of laccase is subject of many researches leading to an increase of interest in new bio-polymers production, namely “environmentally friendly” processes. Enzyme catalysing processes are performed under milder condition requiring less chemical consumption than chemical processes. The coloured polymers enzymatically produced have been studied to introduce in the textile and cosmetic fields by means of colour coatings on fibres and hair. The main objective of this work is the surface modification of cellulosic fibres by means of polymer coating. The polymer production catalysed by laccase was studied using various phenolic substrates. The first attempt to produce suitable polymers was performed with catechol which was easily oxidised by laccase and showed dark colour appearence. In order to attach the polymers “in situ” onto cotton fabrics surface, the functionalisation was preceded. The aminisation was made with a reactive dye forming aromatic amine groups at the cellulose surface, therefore providing a higher ability for polymers coupling. Cotton fabrics coated with the new polymers presented a dark visible colour and high resistance to hydrolysis by cellulase. Non-toxic and non-harmful phenolic substrates such as flavonoids (rutin, morin and quercetin) were further introduced in the laccase reaction medium as potential products for lignocellulosic fabrics colouration. The optimum conditions for polymer production and colouration of fabrics were studied considering several reaction parameters. The level of mechanical agitation and incubation temperature were the decisive factors of colour absorption on fibres. Besides the incubation conditions, the interaction between flavonoids in the reaction medium and the natural flavonoids existing on fibres was also a positive factor proved by higher colour strength and colour resistance through scoured fabrics. Among the used flavonoids, rutin presented the lower polymerisation rate and poor affinity to the fabrics. When the two steps method was used, the polymers were intensively absorbed at high temperature (90°C) due to the enhancement of molecular vibrations both in fibres and in the components of flavonoid solution. The polymers synthesised from flavonoids applied to cotton fabrics showing a good washing fastness (4-5) when incubated at high temperature (90°C) and an excellent friction fastness (5) in all the reaction conditions used. Nevertheless, the weathering fastness was very poor (60% of colour vanishing after 64 hours of light exposure). The elimination of the bleaching step was positively proposed from the conventional textile processes leading to a decrease of pollutant effluents and cost saving. Finally, lignosulfonates were studied as phenolic substrates of laccase. Dynamic instrumental techniques were used to monitor the laccase functions on reaction medium and the physical and chemical substrate changes. The double function of laccase catalysis i.e. polymerisation and depolymerisation was confirmed by Zeta potential and UV-Vis spectrum analysis. The molecular weight increase caused by laccase polymerisation was confirmed by SEC/GPC analysis (MW increased 1700 Da). FT-IR analysis were also performed in order to monitor the structural changes occurred by enzymatic polymerisation. The colouration of flax fabrics with polymerised lignosulfonates was also carried out. The samples coloured with the new compounds, polymerised for 7 days, presented an increase of colour uptake, measured in terms of K/S. The obtained results propose a new concept of bio-polymer production and their practical application on lignocellulosic fibres modification. However, colour fastness is still a limitary factor to take into account on further industrial applications. |
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