H.B.M. Lenting

Identifying important parameters for a continuous bioscouring process

Compared to a bioscouring process in the batch mode, a continuously operating process requires relatively short processing steps. This study focusses on minimizing the required enzymatic incubation time. It is clear that the presence of a sufficient level of surfactant is of major importance in obtaining a satisfying level of water absorbency in a limited time frame. Surprisingly, it is also clear that, although essential, the level of pectin degradation is less important. The most crucial factor in the whole bioscouring process is the removal of the enzyme-weakened cuticle compounds in the rinsing phase. Rinsing at high tem peratures in the presence of surfactant and chelator is most efficient.

Chemical modification of proteases for wool cuticle scale removal

Over the last few decades several enzymatic processes to improve properties of wool fabrics like felting tendency, shrink resistance, dyeing ability and handling characteristics have been described. Previous investigations into the use of proteases to hydrolyse the cuticles at the surface of wool fibres, resulted in high strength and weight losses. Therefore restriction of the enzyme activity to the wool surface or control of enzyme diffusion to the cortex cells is required. To change the diffusion behaviour of proteases in wool fibres, the soluble polymer PEG was covalently attached to a protease from Bacillus lentus. Modified enzymes with different molecular weights were compared. These modified enzymes retained up to 80% of their activity in the standard assay while hydrolysis of wool fibres was successfully restricted to cuticles, resulting in a 90% decrease in weight losses compared to non-modified enzymes.

New Enzyme-based Process Direction to Prevent Wool Shrinking without Substantial Tensile Strength Loss

In this paper a new enzymatic process direction is described for obtaining machine washable wool with acceptable quality. In general, application of protease enzyme technology in wool processing results in considerable loss of tensile strength by diffusion of the enzyme into the interior of wool fibers. To overcome this disadvantage enzymatic activity has been more targeted to the outer surface of the scales by improving the susceptibility of the outer surface scale protein for proteolytic degradation. This has been realized by a pretreatment of wool with hydrogen peroxide at alkaline pH in the presence of high concentrations of salt.

Experimental Investigation of a Polymer Coating in Sliding Contact with Skin-Equivalent Silicone Rubber in an Aqueous Environment

A study on the effect of a brush coating of polyacrylic acid (PAA) grafted with poly(ethylene glycol) (PEG) (PAA-g-PEG) on friction was done for a sliding system that involves silicone skin L7350: a silicone rubber used by the Fédération Internationale de Football Association (FIFA) for the determination of skin–surface friction in combination with artificial grass. Friction experiments were carried out using a reciprocating flat-on-flat test setup with the selected brush coating and compared with PAA-coated and fluoroalkane-coated samples. The experiments were focused on the effect of water. Results for the coatings tested at dry conditions showed a coefficient of friction above 1. Effective lubrication by water was able to reduce friction to a coefficient of friction below 0.01 at low sliding velocities. The results are currently used to further develop low-friction products for sliding interactions with human skin; for example, artificial grass and possibly medical textiles.

Novel protease-based diagnostic devices for detection of wound infection

A gelatinase‐based device for fast detection of wound infection was developed. Collective gelatinolytic activity in infected wounds was 23 times higher (p ≤ 0.001) than in noninfected wounds and blisters according to the clinical and microbiological description of the wounds. Enzyme activities of critical wounds showed 12‐fold elevated enzyme activities compared with noninfected wounds and blisters. Upon incubation of gelatin‐based devices with infected wound fluids, an incubation time of 30 minutes led to a clearly visible dye release. A 32‐fold color increase was measured after 60 minutes. Both matrix metalloproteinases and elastases contributed to collective gelatinolytic enzyme activity as shown by zymography and inhibition experiments. The metalloproteinase inhibitor 1,10‐phenanthroline (targeting matrix metalloproteinases) and the serine protease inhibitor phenylmethlysulfonyl fluoride (targeting human neutrophil elastase) inhibited gelatinolytic activity in infected wound fluid samples by 11–37% and 60–95%, respectively. Staphylococcus aureus and Pseudomonas aeruginosa, both known for gelatinase production, were isolated in infected wound samples.

Industrial production of enzyme‐modified wool fibers for machine‐washable bed coverings

Enzyme technology is explored on wool fibers to prevent shrinkage and consolidation behavior during washing of woolen bed coverings using normal household machine conditions. Enzyme modification of wool fibers after two different pretreatments has been realized on industrial scale. Enlarged proteolytic enzyme by chemical modification was applied successfully to prevent substantial fiber strength loss. Felt-ball analysis of the fibers as obtained from this industrial process showed substantial improvement in felting resistance. Further processing of these enzyme-modified fibers and finally integration in bed covering quilts have been executed successfully on industrial production lines. The observed fiber losses during processing were in the range of 4.5-6% which is comparable with that of nonmodified fibers. The machine-washability of these produced bed covering quilts was tested in a household washing machine using both wool and normal wash programs applied at different temperatures. It appeared that, contrary to the good washing results in terms of shrinkage and consolidation resistance using the wool program at moderate temperatures, this resistance is marginal when washed with the normal washing program with higher mechanical agitation level or with the wool program at elevated temperature. This result was different from that obtained with woolen fabrics and explained by the less-structured organisation of fibers within a fleece.