Béla Koczka

Degradation of lignin-containing materials by xylanase in biopreparation of cotton

Solubilization of lignin and carbohydrates from the lignin-holocellulose structure of cotton seed-coat fragments was investigated by UV/VIS spectrometry. Xylanase (Pulpzyme HC) pre-treatment partially destroyed the lignocellulosic structure of the seed-coat fragments, producing reducing sugars and soluble lignin in the supernatant. Furthermore, the pre-treatment by enzyme enhanced the delignification in the subsequent alkaline scouring process and increased the lightness of the substrate.

Ultrasound-assisted extraction and characterization of hydrolytic and oxidative enzymes produced by solid state fermentation.

Ligninolytic and hydrolytic enzymes were produced with six selected fungi on flax substrate by solid state fermentation (SSF). The extracellular enzyme production of the organisms in two SSF media was evaluated by measuring the soluble protein concentration and the filter paper, endoxylanase, 1,4-β-d-glucosidase, 1,4-β-d-endoglucanase, polygalacturonase, lignin peroxidase, manganese peroxidase and laccase activities of the clear culture solutions produced by conventional extraction from the SSF materials. The SSF material of the best enzyme producer (Trichoderma virens TUB F-498) was further investigated to enhance the enzyme recovery by low frequency ultrasound treatment. Performance of both the original and ultrasound macerated crude enzyme mixtures was evaluated in degradation of the colored lignin-containing and waxy materials of raw linen fabric. Results proved that sonication (at 40%, 60% and 80% amplitudes, for 60min) did not result in reduction in the filter paper, lignin peroxidase and laccase activities of the crude enzyme solution, but has a significant positive effect on the efficiency of enzyme extraction from the SSF material. Depending on the parameters of sonication, the enzyme activities in the extracts obtained can be increased up to 129-413% of the original activities measured in the control extracts recovered by a common magnetic stirrer. Sonication also has an effect on both the enzymatic removal of the lignin-containing color materials and hydrophobic surface layer from the raw linen.

Effect of particle size on the surface properties and morphology of ground flax.

Flax fibers were ground with a ball-mill and four fractions with different size ranges were collected by sieving. These were tested for water sorption, degree of polymerization (DP), copper number, hydroxyl number and analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and inverse gas chromatography (IGC). Significant differences were found between the properties of the flax fiber and those of the ground versions, including fragmentation of fibers, increase of water sorption, copper number, hydroxyl number and surface O/C ratio, and decrease of DP, crystallite size and dispersive component of surface energy (γs(d)). Some parameters depended on the particle size: O/C ratio and hydroxyl number had local maxima at 315-630 μm, while γs(d) increased steadily with the decrease of particle size. These relationships were explained by fiber disintegration, destruction of waxy surface layer, exposure of cellulosic components, increase of surface area and crystalline imperfections.

Effect of hydrolytic and oxidative enzymes produced by solid-state fermentation on greige linen fabric

Solid state fermentation (SSF) was applied for production of fungal enzyme preparations from Phanerochaete chrysosporium, Aspergillus oryzae, Aspergillus giganteus and Trichoderma virens using cotton seed-coat fragment waste as a carbon source and enzyme inducer. Lignin-holocellulose matrix of cotton seed coat fragment proved to be effective in inducing production of ligninolytic, cellulolytic and xylanolytic enzymes in solid-state fermentation. The effect of the enzymes produced by SSF on greige linen fabric is discussed and evaluated. In the first experiment the hydrolytic and accompanying oxidative enzymes in the buffer extract of the whole SSF cultures were used for fabric treatment. In the second trial, the enzymes produced in situ (whole SSF material—mixture of fungal biomass, residual substrate and enzymes) were used for the treatment. Weight loss, reducing sugar liberation and removal of colouring materials were measured. The results showed that at equal enzyme charges the intact SSF materials were more efficient than the enzyme extracts. Of the six strains evaluated, Ph. chrysosporium VKM F-1767 was the most effective in removing colouring matters from greige linen fabric.

Enhancing the accessibility of starch size and cellulose to enzymes in raw cotton woven fabric by air-plasma pretreatment

In this paper, raw cotton fabric was pretreated with non-thermal atmospheric air-plasma and the accessibility of the surface polymers of the fibers and yarns that act as respective substrates for the enzymes was evaluated. Results proved that plasma slightly destroyed and oxidized the starch size on the surface of warp yarns and partially removed the thin and perfectly hydrophobic waxy coverage of the fibers in weft yarns, creating deep “pits” with a depth of 215 nm. This latter process contributed to the exposure of cellulose and pectin located under the waxy outer layer of the elementary fibers in the weft yarns, and significantly increased the surface roughness of the fibers (from Rq of 25 to 67 nm for the raw and 180 s plasma-treated samples, respectively). Amount of the reducing sugars released during the amylase and cellulase digestion of the plasma-treated fabrics confirmed that air-plasma significantly increased the accessibility of the starch and cellulose, respectively, to the enzymes and resulted in an enhanced solubilization of both polymers. Since the plasma-treated substrates displayed significantly faster enzyme reactions, the time of enzymatic treatments can be sharply reduced.

Cellulose nanocrystal/amino-aldehyde biocomposite films

From the suspensions of cellulose nanocrystals (CNCs) derived from cotton and flax by acidic hydrolysis, transparent and smooth films were produced with different plasticizers and an amino-aldehyde based cross-linking agent in a wide composition range by a simultaneous casting and wet cross-linking process. The effect of cross-linker concentration on the optical and tensile properties and on the morphology of CNC films was investigated by various measurements. The interaction of films with liquid water and water vapour was also characterized by water sorption and water contact angle as well as performing a sinking test. Cross-linking improved the transparency, reduced the porosity and surface free energy, and prevented the delamination of CNC films in water at a concentration of 10% or higher. The surface of CNC films is basic in character and has an electron donor property. The CNC/amino-aldehyde films had a high tensile strength (45 MPa) and modulus (11 GPa).