Critical Point Drying: An Effective Drying Method for Direct Measurement of the Surface Area of a Pretreated Cellulosic Biomass.

Kyu-Young Kang,Kyung-Ran Hwang,Jin-Suk Lee,Joon-Pyo Lee,Ji-Yeon Park,Jun-Seok Kim

doi:10.3390/polym10060676

Kyu-Young Kang, Kyung-Ran Hwang + Show 4 more

Open Access

https://doi.org/10.3390/polym10060676

Copy DOI

Abstract

The surface area and pore size distribution of Eucalyptus samples that were pretreated by different methods were determined by the Brunauer–Emmett–Teller (BET) technique. Three methods were applied to prepare cellulosic biomass samples for the BET measurements, air, freeze, and critical point drying (CPD). The air and freeze drying caused a severe collapse of the biomass pore structures, but the CPD effectively preserved the biomass morphology. The surface area of the CPD prepared Eucalyptus samples were determined to be 58–161 m2/g, whereas the air and freeze dried samples were 0.5–1.3 and 1.0–2.4 m2/g, respectively. The average pore diameter of the CPD prepared Eucalyptus samples were 61–70 Å. The CPD preserved the Eucalyptus sample morphology by replacing water with a non-polar solvent, CO2 fluid, which prevented hydrogen bond reformation in the cellulose.

Highlights

For the efficient sugar fractionation from the lignocellulosic biomass, physical contact between cellulose and cellulase enzymes is necessary
The surface area and pore size distribution of the samples were determined by BET and the differences were compared among the critical point drying (CPD), air drying (AD), and freeze drying (FD) pretreatments
The pore collapse in the cellulose fibers was more significant during the AD procedure than the FD, based on their adsorbed quantity

Summary

Introduction

For the efficient sugar fractionation from the lignocellulosic biomass, physical contact between cellulose and cellulase enzymes is necessary. The cellulose specific surface area that is available for enzyme contact is one of the most important factors for determining the rate and extent of the enzymatic hydrolysis of the biomass [1,2,3]. Since the average size of cellulase enzymes is approximately 5.1 nm, the internal surface of the pores that are greater than 5.1 nm should be effective for enzymatic hydrolysis [4]. Most studies regarding the biomass specific surface area and pore size distribution have employed indirect measurement techniques, such as solute exclusion [5,6,7,8], non-hydrolytic protein adsorption [9], Simons’ staining [10,11,12], and NMR techniques [13,14].

Methods

Results

Conclusion