Klaus Opwis

Inhibition of microbial pathogens by fungal chitosan

Four fungal chitosan types (CTS) were prepared from Mucor rouxii DSM 1191 and examined for their physico-chemical characteristics. The antimicrobial activity of chitosan types against 11 bacterial strains, including six pathogens, was investigated and the most effective type was chitosan No. 3 which was characterized with the lowest viscosity and molecular weight (3.1 cP and 2.1 x 10(4)Da, respectively), the highest degree of deacetylation (95%) and neutral water solubility. Gram positive bacteria were generally more sensitive to chitosan antimicrobial action than Gram negative strains and this action was notably affected by the environmental growth conditions, i.e. incubation temperature and pH value. The applications of fungal chitosan for the suppression of bacterial pathogens as a natural alternative, reduced risk and biodegradable biocidal agent could be recommended.

Anticandidal action of fungal chitosan against Candida albicans

The anticandidal activity of four fungal chitosan types, produced from Mucor rouxii DSM-1191, against three Candida albicans strains was determined. The most bioactive chitosan type, to inhibit C. albicans growth, had the lowest molecular weight (32 kDa) and the highest deacetylation degree (94%). Water soluble types had stronger anticandidal activity than soluble types in 1% acetic acid solution. Scanning electron micrographs of treated C. albicans with fungal chitosan proved that chitosan principally interact with yeast cell wall, causing severe swelling and asymmetric rough shapes, and subsequent cell wall lyses with the prolonging of exposure time. Fungal chitosan could be recommended for C. albicans control as a powerful and safe alternative to synthetic and chemical fungicides.

Recent Approaches to Highly Hydrophobic Textile Surfaces

A super-hydrophobic character is increasingly required for high-performance technical textiles in order to attain effective liquid repellence, self-cleaning, uni-directional liquid transport, or to create barrier coatings on fiber surfaces. Accordingly, numerous novel approaches to decrease the surface free energy of fibers have been studied in the last years, either employing wet-chemical finishes based on modern chemical developments such as silane chemistry, nanocomposite structures, or physically applied thin layers. Similar to other branches, textile researchers have also tried to mimic the extreme water repellence of several plant and animal surfaces according to the understanding by Cassie and Baxter. The scope of this paper is to give a critical overview of the principles, advantages and disadvantages of several concepts. While leading to high water or even oil repellence, chemical finishes applied using conventional methods — i.e. dipping or padding and ensuing thermal fixation — mostly fail to withstand influences such as mechanical stress — e.g. abrasion, high tensile forces —, climate, aggressive chemical environments, and high temperatures, to which technical textiles are subjected to in use. This is true for conventional fluorocarbons or novel finishes such as silicones. Here, cross-linked layers of non-polar character prove to be superior. These can either be obtained by deposition of inorganic–organic nanocomposites, e.g. using the sol–gel technique, or by deposition of thin layers by physical methods. With regard to the effects of microrough fiber surfaces, present knowledge indicates an inferior durability due to the destruction of the delicate topography in use. In natural systems such as plants, this effect is overcome by self-healing mechanisms which technical products do not possess.

Antimicrobial textile treated with chitosan from Aspergillus niger mycelial waste

The waste biomass of Aspergillus niger, following citric acid production, was used as a source for fungal chitosan extraction. The produced chitosan was characterized with deacetylation degree of 89.6%, a molecular weight of 25,000 dalton, 97% solubility in 1% acetic acid solution and comparable FT-IR spectra to standard shrimp chitosan. Fungal chitosan was applied as a cotton fabric finishing agent using pad-dry-cure method. The topographical structure of chitosan-treated fabrics (CTF) was much improved compared with control fabrics. CTF, after durability tests, exhibited a powerful antimicrobial activity against both E. coli and Candida albicans, the captured micrographs for E. coli cells contacted with CTF showed a complete lysis of cell walls with the prolonging contact time. The produced antimicrobial CTF could be proposed as a suitable material for many medical and hygienic applications.

Permanent flame retardant finishing of textiles by allyl-functionalized polyphosphazenes.

Despite their excellent flame retardant properties, polyphosphazenes are currently not used as flame retardant agents for textile finishing, because a permanent fixation on the substrate surface has failed so far. Here, we present the successful synthesis and characterization of a noncombustible and foam-forming polyphosphazene derivative, that can be immobilized durably on cotton and different cotton/polyester blended fabrics using photoinduced grafting reactions. The flame retardant properties are improved, a higher limiting oxygen index is found, and the modified textiles pass several standardized flammability tests. As flame retardant mechanism a synergistic effect between the immobilized polyphosphazene and the textile substrate was observed. The polyphosphazene finishing induces an earlier decomposition of the material with a reduced mass loss in thermogravimetric analysis. The decomposition of cotton and polyester leads to the formation of phosphorus oxynitride, which forms a protecting barrier layer on the fiber surface. In addition, the permanence of the flame retardant finishing was proven by laundry and abrasion tests.

Enzymatic Recycling of Starch-Containing Desizing Liquors

Starch-containing desizing liquors from the pretreatment of cotton fabrics can be transformed into bleaching liquors by a two-stage enzymatic treatment. The bleaching ability of these liquors is comparable to that of conventional bleaching liquors. The process results in saving of ecologically harmful chemicals and process water. In enzymatic textile processes a loss of enzyme activity occurs, due to the presence of ionic surfactants. This loss of activity can be counteracted by addition of cyclodextrins. Trials have been done to immobilize glucose oxidase on the cheap carrier material cotton, so it can be used more often than only one time as regenerable enzyme.

Semi-industrial production of methane from textile wastewaters

BackgroundThe enzymatic desizing of starch-sized cotton fabrics leads to wastewaters with an extremely high chemical oxygen demand due to its high sugar content. Nowadays, these liquors are still disposed without use, resulting in a questionable ecological pollution and high emission charges for cotton finishing manufacturers.MethodsIn this paper, an innovative technology for the production of energy from textile wastewaters from cotton desizing was developed. Such desizing liquors were fermented by methane-producing microbes to biogas. For this purpose, a semi-industrial plant with a total volume of more than 500 L was developed and employed over a period of several weeks.ResultsThe robust and trouble-free system produces high amounts of biogas accompanied by a significant reduction of the COD of more than 85%. With regard to growing standards and costs for wastewater treatment and disposal, the new process can be an attractive alternative for textile finishing enterprises in wastewater management, combining economic and ecological benefits.ConclusionMoreover, the production of biogas from textile wastewaters can help to overcome the global energy gap within the next decades, especially with respect to the huge dimension of cotton pretreatment and, therefore, huge desizing activities worldwide.

Surface modification of textile materials with hydrophobins

Hydrophobins are native proteins with outstanding properties. Because of their special bifunctional molecular structure they can influence the wetting behavior of polymeric substrates. Here, the influence of thermally deposited hydrophobins on properties of various textile substrates is studied. The successful immobilization of hydrophobins can be demonstrated by a protein-selective color reaction with ninhydrin, which is positive even after a harsh washing and extraction procedure indicating the high permanence of the finishing process. Regarding the wetting properties, the modification of hydrophobic fabrics (demonstrated on polyethylene terephthalate) results in a significant hydrophilization, while hydrophilic textile substrates made of cotton and polyamide attain strong hydrophobic character. Moreover, the developed thermal deposition technique seems to be practical for use with coating technologies established in the textile industry and could be easily transferred to industrial praxis. Thus, non-toxic and biodegradable hydrophobins copied from nature could have great potential in textile surface modification.

Antibacterial action of acetic acid soluble material isolated from Mucor rouxii and its application onto textile

Acetic acid soluble material (AcSM) is a chitosan-rich fraction isolated from the fungal cell wall materials. The final step in the traditional production of fungal chitosan is the separation of chitosan from the cell wall AcSM via raising the pH to 9-10 followed by centrifugation. This step results in further undesirable economic and environmental effects. The goal of this paper is to avoid that by investigating the antimicrobial effect of the whole AcSM from Mucor rouxii DSM-1191 cell wall and its application on cotton fabrics. The treated fabrics were characterized through monitoring the textile physical properties and for the antibacterial activity against Escherichia coli and Micrococcus luteus. Results showed that Mucor rouxii DSM-1191 has excellent potentials to be used for cell wall AcSM production on industrial scale with a maximum content of 40% in dry mycelia. The obtained results indicated that the physical properties of the treated fabrics, as well as the antibacterial activity, were improved after treatment with fungal AcSM.

Textile Catalysts—An unconventional approach towards heterogeneous catalysis

Textile catalysts are a new approach utilizing immobilization of different classes of catalysts onto textile materials such as polyethylene terephthalate and polyamide. Robust, inexpensive fibrous materials are chosen because they are available in many variations. By a photochemical approach a series of different supported organocatalysts (organotextile catalysts) has been prepared, showing high catalytic activity and good reusability. The aim of this concept article is to present the scope, limits and open questions of our innovative approach. The working principle of the immobilization and its control parameters will be explained and the scope of useable catalysts is shown. Therefore we will show the significant influence of the anchoring group on loading and more importantly on catalyst activity. This concept is also applicable to organometallic catalysts and enzymes. Understanding the different phenomena allows us to develop “textile catalysts” as a new powerful tool for heterogeneous catalysis.