Enzymatic degradation of model cellulose films

doi:10.1016/j.jcis.2004.10.041

Journal of Colloid and Interface Science

Volume 284, Issue 1, 1 April 2005, Pages 99-106

https://doi.org/10.1016/j.jcis.2004.10.041 Get rights and content

Abstract

Enzymatic degradation of model cellulose films prepared by a spin-coating technique was investigated by ellipsometry. The cellulose films were prior to degradation characterized by ellipsometry, contact angle measurements, ESCA (electron spectroscopy for chemical analysis) and AFM (atomic force microscopy). At enzyme addition to preformed cellulose films an initial adsorption was observed, which was followed by a total interfacial mass decrease due to enzymatic degradation of the cellulose films. The degradation rate was found to be constant during an extended time of hours, whereafter the degradation leveled off. In parallel to the decreased interfacial mass, the cellulose degradation resulted in a thinner and more dilute interfacial film. At long degradation times, however, there was an expansion of the cellulose film. The enzyme concentration affected the degradation rate significantly, with a faster degradation at a higher enzyme concentration. The effects of pH, temperature, ionic strength and stirring rate in the cuvette were also investigated.

Introduction

With the development of protein engineering, new enzymes are discovered and developed at an increasing rate. Today, enzymes are used in several industrial contexts, and new applications are constantly being investigated and developed in such a wide variety as wound healing, removal of dental plaque, detergency, food processing, high throughput in biotechnical analysis systems and as a tool for specific organic synthesis [1], [2], [3], [4], [5], [6], [7], [8]. Cellulases, investigated in the present study, are interesting for paper and fiber applications, e.g., in the retention step or in deinking for paper recirculation as well as textile treatment and detergency [9], [10], [11], [12], [13], [14].

The controlled use of enzymes in these and other applications relating to surface modifications requires knowledge of the different processes occurring when an enzyme is put in contact with a substrate surface/film to be degraded or otherwise modified. Parallel to the degradation, there may also be adsorption of both the enzyme and the reaction products. Both the degradation and the adsorption may also affect the accessibility of the substrate to enzymatic degradation. These and other effects call for investigations of enzymatic degradation of interfacial substrates, and although there has been an increased interest in the area during recent years [3], [9], [10], [13], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], there is still a great challenge to employ and improve these processes in a controlled way. Ellipsometry has been shown to be a useful technique in such explorations [19], [26], [27]. With this as a background, we therefore initiated the present investigation, focusing on ellipsometric investigations of the degradation of interfacial cellulose films. In this first investigation, a mixed enzyme system extensively used in practical and industrial applications [24] was studied, whereas more mechanistic studies of the role of different enzyme structure elements are summarized in a separate publication [28].

Section snippets

Materials

Microcrystalline cellulose (Avicel), $N, N$ -dimethylacetamide (for synthesis) and lithium chloride (pro analysis) was purchased from Merck, Germany, and used as delivered. Cationic polyacrylamide (AM-MAPTAC) from Allied Colloids, UK, was used as an “adhesion promotor” in the spin-coating procedure. This polymer consists of acrylamide (AM) and (methacrylamidopropyl)trimethylammonium chloride (MAPTAC) monomers, and has a molecular weight of 10⁶ g mol⁻¹ and 50.5 mol% charged MAPTAC units.

The

Cellulose films in dry state

The films obtained by spin coating from a 1 wt% cellulose solution displayed an ellipsometric mean thickness and refractive index, in the dry state, of $28 \pm 3 nm$ and $1.56 \pm 0.01$ , respectively. Particularly within each batch of substrates the standard deviation was low (±1), while the batch-to-batch variation was found to be somewhat larger, up to $\pm 3 nm$ difference in mean thickness. Using a lower cellulose concentration in the coating solution was found to result in thinner layers, as also found by

Summary

The model cellulose films produced and investigated were found to be easy to prepare, relatively smooth, pure, and pinhole-free. They are also sufficiently stable in aqueous solutions after an initial equilibrium time, and also when exposed to polyelectrolytes and surfactants. At the same time, they are accessible to enzymatic degradation. Hence, the surfaces prepared offer a range of opportunities in relation to model investigations of interfacial processing of cellulose. Using these model

Acknowledgments

Dr. Andrew Fogden is gratefully acknowledged for helpful discussions, while Marie Ernstsson and Mikael Sundin are thanked for support with the ESCA analysis. Jonny Eriksson acknowledges the support from the Colloid and Interface Technology Programme, financed by the Swedish Foundation for Strategic Research (SSF). Sponsorship from Novozymes A/S is also gratefully acknowledged.

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Enzymatic degradation of model cellulose films

Abstract

Introduction

Section snippets

Materials

Cellulose films in dry state

Summary

Acknowledgments

Colloid Surf. B Biointerfaces

J. Mol. Catal. B Enzym.

J. Biotechnol.

Biotechnol. Adv.

Ultramicroscopy

J. Biotechnol.

J. Biotechnol.

J. Biotechnol.

J. Biol. Chem.

Colloid Surf. B Biointerfaces

J. Colloid Interface Sci.

Polymer

J. Biotechnol.

J. Colloid Interface Sci.

FEBS Lett.

Biochem. J.

Int. J. Dermatol.

Eur. J. Oral Sci.

Extremophiles

Anal. Chem.

J. Am. Oil Chem. Soc.

Cellulose

Biochemistry (Moscow)

Biopolymers

Langmuir