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Comparison of microwave-assisted zinc chloride hydrate and alkali pretreatments for enhancing eucalyptus enzymatic saccharification

Wei, Weiqi, Zhang, Hongdan, Jin, Yongcan
Energy conversion and management 2019 v.186 pp. 42-50
Eucalyptus, alkali treatment, cellulose, crystal structure, endo-1,4-beta-glucanase, energy conservation, enzymatic hydrolysis, feedstocks, glucose, heat, hemicellulose, hydrolysis, lignin, microwave radiation, microwave treatment, polysorbates, saccharification, sodium hydroxide, zinc chloride
In this work, four kinds of pretreatment methods including microwave-assisted ZnCl2·4H2O or NaOH pretreatment, traditional electrical heating ZnCl2·4H2O or NaOH pretreatment were developed and compared for eucalyptus hydrolysis at 100 °C. The effect of various pretreatment methods on hemicellulose and lignin degradation, and as well as subsequent pretreated solids enzymatic saccharification were completely investigated. The results showed that microwave-assisted ZnCl2·4H2O pretreatment was highly successful for enhancing eucalyptus enzymatic saccharification due to the removal of hemicellulose and the change of cellulose crystal structure. The pretreatment time can be significantly shortened from 90 min to 20 min by using microwave irradiation as a heating manner, which means energy saving. The addition of Tween 80 into enzymatic hydrolysis step could remarkably reduce the cellulase dosage while the glucose yields do not decrease. The highest glucose yield of this work was 35.7 g/100 g raw material, which represented 90.6% glucose in eucalyptus feedstock. It could be concluded that combination of ZnCl2·4H2O and microwave irradiation provided an applicable strategy for enhancing sugars release from eucalyptus.