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Open Access Research

Derivatization-free gel permeation chromatography elucidates enzymatic cellulose hydrolysis

Philip Engel1, Lea Hein1 and Antje C Spiess12*

Author Affiliations

1 AVT-Enzyme Process Technology, RWTH Aachen University, Worringerweg 1, Aachen, 52056, Germany

2 Interactive Materials Research, DWI an der RWTH Aachen e.V, Forckenbeckstr. 50, Aachen, 52074, Germany

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Biotechnology for Biofuels 2012, 5:77  doi:10.1186/1754-6834-5-77

Published: 12 October 2012

Abstract

Background

The analysis of cellulose molecular weight distributions by gel permeation chromatography (GPC) is a powerful tool to obtain detailed information on enzymatic cellulose hydrolysis, supporting the development of economically viable biorefinery processes. Unfortunately, due to work and time consuming sample preparation, the measurement of cellulose molecular weight distributions has a limited applicability until now.

Results

In this work we present a new method to analyze cellulose molecular weight distributions that does not require any prior cellulose swelling, activation, or derivatization. The cellulose samples were directly dissolved in dimethylformamide (DMF) containing 10-20% (v/v) 1-ethyl-3-methylimidazolium acetate (EMIM Ac) for 60 minutes, thereby reducing the sample preparation time from several days to a few hours. The samples were filtrated 0.2 μm to avoid column blocking, separated at 0.5 mL/min using hydrophilic separation media and were detected using differential refractive index/multi angle laser light scattering (dRI/MALLS). The applicability of this method was evaluated for the three cellulose types Avicel, α-cellulose and Sigmacell. Afterwards, this method was used to measure the changes in molecular weight distributions during the enzymatic hydrolysis of the different untreated and ionic liquid pretreated cellulose substrates. The molecular weight distributions showed a stronger shift to smaller molecular weights during enzymatic hydrolysis using a commercial cellulase preparation for cellulose with lower crystallinity. This was even more pronounced for ionic liquid-pretreated cellulose.

Conclusions

In conclusion, this strongly simplified GPC method for cellulose molecular weight distribution allowed for the first time to demonstrate the influence of cellulose properties and pretreatment on the mode of enzymatic hydrolysis.

Keywords:
Cellulose molecular weight; Gel permeation chromatography; Eluent for underivatized cellulose