Effect of electron‐beam irradiation pretreatment on the enzymatic hydrolysis of softwood

Abstract

Tests made using electron-beam irradiation for the pretreatment of spruce wood showed that over 90% cellulose present in samples treated with a maximum dose of 2 MGy was converted to sugars by Trichoderma cellulase. The enzymatic hydrolysis of these samples was completed in 24 h, and the sugar solutions produced contained over 88% glucose, the remainder was cellobiose, xylose, and mannose. After irradiation treatment, spruce wood chips were comparable to untreated filter-paper cellulose for enzymatic saccharification. The results suggest that electron beam irradiation is technically feasible as a pretreatment for enzymatic hydrolysis of a softwood.Enzymatic saccharification of cellulose as compared to acid hydrolysis decreases the formation of unwanted by products and is more efficient.' However, for the enzymatic conversion of lignocellulosic biomass to sugars, a pretreatment is required to destroy the lignocellulosic association, to reduce the cellulose crystallinity and to increase the available surface for enzymatic attack. For this purpose, a number of chemical, mechanical, steam, and pressure pretreatments have been studied.24 Many studies have shown that these methods are less effective on softwoods than hardwoods.S.6 More recently, the work carried out by Kumakura and Kaetsu7-'0 has demonstrated the usefulness of irradiation as pretreatment for improving enzymatic hydrolysis of bagasse, chaff, rice straw, sawdust, and wastepaper. This communication describes results of enzymatic hydrolysis of irradiated wood from spruce, a softwood species. MATERIALS AND METHODS Irradiation SourceSpruce wood chips were irradiated with 4-MeV electrons using the Chalk River Electron Test Accelerator." Figure 1 shows a sketch of the continuous-wave linear accelerator, which is capable of producing beams of up to 20 mA. The accelerator is composed of four side-coupled structures operating at 805 MHz, driven in pairs through bridge couplers from two 100 kW klystrons. There are three experimental areas. In line with the accelerator, bremsstrahlung targets are being developed. The electron beam can be brought out into air through a thin window in the 45" beam line where new applications for high power electron beam irradiations can be investigated. Advanced linear accelerator structure designs can be tested in the 90" beam line. Figure 2 shows a sketch of the setup used during the wood chip irradiations. The electron beam was defocussed on the samples with a solenoid lens. The beam current density used was 0.3 pA/cm2. The beam uniformity over the sample area was better than 10%. Samples were maintained at room temperature during the irradiations by cooling the sample container with circulating water. The dose rate was 2 MGy/h. Method of IrradiationThe irradiation dose was obtained from a measurement of the integrated charge. The dose in MGy is given by dE dt D = i o 3 -~where dE/dt is the electron stopping power of the medium (ca. 1.9 MeV cmYg for 4-MeV electrons) and Q

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

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Effect of gamma irradiation pretreatment on biodegradation of forest lignocelluloses byAspergillus niger

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