Gisela Buschle-Diller

Structural Changes in Hemp Fibers as a Result of Enzymatic Hydrolysis with Mixed Enzyme Systems

Hemp fabric is hydrolyzed with cellulase, hemicellulase/cellulase, and cellulase plus additional β-glucosidase. The effect of the admixture of hemicellulase and β-glucosi dase is evaluated in terms of hydrolysis rate and product properties. The influence of mechanical action during the treatment is also taken into account. Treated samples are characterized by weight loss per incubation time, tensile strength, crystallinity, acces sibility, and pore structure. The admixture of hemicellulase and,β-glucosidase produces only minor effects without mechanical action on the hydrolysis rate, but mechanical action applied during the treatment dramatically increases weight loss. While crystal linity changes upon hydrolysis are insignificant, the pore structure is strongly influenced by the choice of enzyme system. Hemicellulase seems to promote the formation of smaller pores, while cellobiase forms larger pores.

Enzymatic Bleaching of Cotton Fabric with Glucose Oxidase

Cotton fabric is desized with amyloglucosidase and combined with bioscouring with two different kinds of pectinase in the presence and absence of cellulase. The treatment bath, rich in glucose, is initially reused for biobleaching with glucose oxidase under neutral conditions. Finally, all three preparatory processes are combined. The whiteness, water absorbency, tensile strength, and degree of polymerization of the treated cotton goods are evaluated. The process yields products with acceptable whiteness very close to the whiteness of commercially bleached goods and excellent mechanical properties. The amount of rinse water can be drastically reduced.

Modified Fibers with Medical and Specialty Applications

The research and development of chronic wound dressings, which possess a mechanismbased mode of action, has entered a new level of understanding in recent years based on improved definition of the biochemical events associated with pathogenesis of the chronic wound. Recently, the molecular modes of action have been investigated for skin substitutes, interactive biomaterials, and some traditional material designs as balancing the biochemical events of inflammation in the chronic wound to improve healing. The interactive wound dressings have activities including up-regulation of growth factors and cytokines and down-regulation of destructive proteolysis. Carbohydrate-based wound dressings have received increased attention for their molecular interactive properties with chronic and burn wounds. Traditionally, the use of carbohydrate-based wound dressings including cotton, xerogels, charcoal cloth, alginates, chitosan, and hydrogels have afforded properties such as absorbency, ease of application and removal, bacterial protection, fluid balance, occlusion, and elasticity. Recent efforts in our lab have been underway to design carbohydrate dressings that are interactive cotton dressings as an approach to regulating destructive proteolysis in the non-healing wound. Elastase is a serine protease that has been associated with a variety of inflammatory diseases and has been implicated as a destructive protease that impedes wound healing. The presence of elevated levels of elastase in non-healing wounds has been associated with the degradation of important growth factors and fibronectin necessary for wound healing. Focus will be given to the design, preparation, and assessment of a type of cotton-based interactive wound dressing designed to intervene in the pathophysiology of the chronic wound through protease sequestration.

INFLUENCE OF DIRECT AND REACTIVE DYES ON THE ENZYMATIC HYDROLYSIS OF COTTON

Cotton fabric is subjected to enzymatic hydrolysis with cellulases before and after dyeing. The effects of direct dyes of increasing molecular size on the rate of the en zymatic hydrolysis reaction are investigated, along with mono- and bifunctional reac tive dyes with different functional groups. All reactive dyes studied and especially bifunctional reactive dyes, have a decelerating influence on enzymatic attack. The effect of the direct dyes depends strongly on the enzymatic treatment duration. Moisture regain values of enzyme treated fabric suggest a transient state of somewhat increased disorder of the cellulose structure at a specific stage of hydrolysis, which is alleviated by longer incubation times. At this stage, direct dyed fabric shows a hydrolysis rate approximately equal to or slightly higher than undyed fabric.

Effect of cellulase on the pore structure of bead cellulose

An enzymatic treatment with cellulases fromTrichoderma viride was investigated in its effect on the pore structure of different types of bead cellulose. One objective of this study was to establish a suitable procedure for combined enzymatic treatment and solvent exchange that would restore the original pore structure which the beads had before drying without causing major losses in mechanical stability. Another aim was to further increase the accessible pore space and internal surface area for separation of large molecular weight compounds with regard to Chromatographic applications. Finally, an attempt was made to extend the findings for unsubstituted beads to the derivatives carboxymethyl (CM) and diethylaminoethyl (DEAE) cellulose beads. The enzymatically treated samples were characterized by microscopic methods and porosity measurements such as mercury porosimetry, nitrogen sorption and size exclusion chromatography. It was found that under controlled conditions the low-porosity surface layer of dried beads could be removed making the internal pore space accessible without reducing the resistance to deformation of the beads. Additionally, a shift in pore size distribution towards larger pores was observed. Supplementary swelling treatments in solvents of high swelling power could substantially restore the former porosity of the dried beads but did not enhance the accessibility to the cellulases to a considerable extent. Internal pore volume and surface area of the derivatives were dramatically increased in the case of DEAE upon enzymatic hydrolysis, however, at the expense of mechanical stability, whereas CM was found to be less affected.

Electrospun Nanofibers from Biopolymers and Their Biomedical Applications

With the help of the electrostatic spinning technology, biopolymers can be formed into nanofibrous structures which have great potential for medical applications. Due to their small size, the electrospun fibers provide a large surface-to-volume ratio and could be used for drug delivery, scaffolds for tissue engineering, or provide support for bone repair. Due to the relative ease of the electrospinning technique a large number of different polymeric materials including natural fibers have already been explored or will be in the near future. Carefully tailored surface chemistries of these micro- and nanofibers will continue to expand their applications in the medical field.

Enzymatic Modification of Fibers for Textile and Forest Products Industries

Avariety of enzymes are available for the surface modification of cellulosic fibers, both in the area of textile applications and for pulp and paper applications. Enzymatic treatment conditions are milder, less damaging for the fiber, and are environmentally friendly while producing effects comparable to chemical treatments. Surface modifications can be achieved by oxidative and/or hydrolytic enzymes. Some of the enzymatic processes have recently attained commercial importance and more systems are being developed. The following chapter will review current research in the application of oxidoreductases and hydrolases that are valuable for textile and forest products industries.

Formulation and characterization of polysaccharide beads for controlled release of plant growth regulators

Owing to their chemical, physical, and functional characteristics, polysaccharides are considered to be the most versatile natural polymers. As a result, their properties have been exploited in various fields of research in the biomedical, pharmaceutical, cosmetic, food, and agricultural industries. A property of special interest is their ability to form systems or materials with unique physicochemical characteristics, such as hydrogels and micro- and nanoparticles for controlled release of active compounds. In the present study, polysaccharide beads formulated from alginate, cellulose powder, cellulose nanocrystals, starch, and xylan were reinforced with kaolin and surface-modified with polyethylenimine (PEI), a positively charged polyelectrolyte. Addition of kaolin improved the mechanical strength of the beads. Modification of the surface of the beads with PEI facilitated better control of the release rate of the plant growth regulator, phenylacetic acid (PAA). The physical properties of the beads were characterized by optical and scanning electron microscopy, and their mechanical strength was determined by an Instron 5565 Tensile Testing Machine. Cumulative release of PAA was measured by UV–Vis spectroscopy.

The effect of ethanol on hydroxyl and carbonyl groups in biopolyol produced by hydrothermal liquefaction of loblolly pine: (31)P-NMR and (19)F-NMR analysis.

The goal of this study was to investigate the role of ethanol and temperature on the hydroxyl and carbonyl groups in biopolyol produced from hydrothermal liquefaction of loblolly pine (Pinus spp.) carried out at 250, 300, 350 and 390°C for 30min. Water and water/ethanol mixture (1/1, wt/wt) were used as liquefying solvent in the HTL experiments. HTL in water and water/ethanol is donated as W-HTL and W/E-HTL, respectively. It was found that 300°C and water/ethanol solvent was the optimum liquefaction temperature and solvent, yielding up to 68.1wt.% bio-oil and 2.4wt.% solid residue. (31)P-NMR analysis showed that biopolyol produced by W-HTL was rich in phenolic OH while W/E-HTL produced more aliphatic OH rich biopolyols. Moreover, biopolyols with higher hydroxyl concentration were produced by W/E-HTL. Carbonyl groups were analyzed by (19)F-NMR, which showed that ethanol reduced the concentration of carbonyl groups.

Chitosan-based injectable hydrogels for biomedical applications

Chitosan is a natural polymer, which has similar structure and bioactivity with glycosaminoglycan, and is a potential material for use as injectable hydrogels. Authors elucidate structure–property relationship with particular focus on chitosan-based injectable hydrogels, and their application as biomaterials. The different gelation approach, including physical cross-link, chemical cross-link, ionic cross-link and supramolecular interaction, enable a variety of chitosan-based injectable hydrogels to be formed. These gelation methods have significant impact on the structure and properties of hydrogels, which governs their use as tissue engineering scaffold and drug delivery vehicle.