Low level of enzymatic susceptibility of microwave-pretreated softwood

Microwave pretreatment improves the enzymatic susceptibility of hardwood (buna, Fagus crenata), but has limited effect on softwood (akamatsu, Pinus densiflora). A study was made of chemical changes during microwave irradiation at 160°-220°C of ground wood of these species. Pore width began to increase at a lower temperature in akamatsu than in buna, but pore volume increased very little in akamatsu. Multiple regression analysis showed that partial degradation of cellulose caused the swelling of cell walls. Quantitative analysis revealed a distinct difference in lignin degradation between buna and akamatsu. Microwave irradiation caused lignin condensation in the softwood, thus inhibiting an increase in surface area available for enzymatic hydrolysis