Keqin Wang

Comparison of γ-irradiation with other pretreatments followed with simultaneous saccharification and fermentation on bioconversion of microcrystalline cellulose for bioethanol production.

The effect of γ-irradiation pretreatment was compared with other pretreatment methods including ionic liquids (ILs), 1% HCl, 1% H2SO4, acidic aqueous Ils (AA-ILs), on the bioconversion efficiency of microcrystalline cellulose (MCC) for bioethanol production. The efficiency of MCC pretreatment followed with simultaneous saccharification and fermentation (SSF) was firstly evaluated according to the variations of the irradiation-derived compounds and structure of MCC, as well as yeast growth curve and bioethanol yield. Results showed that the appropriate irradiation dose (891 kGy used in our work) could eliminate the negative effect of toxic irradiation-derived compounds on SSF for ethanol bioconversion with the yield value of 67%. Analyses of SEM, FT-IR, reducing sugar and bioethanol yield showed that the efficiency of pretreatment on MCC was ILs ≈ irradiation pretreatment > AA-ILs pretreatment > 1% HCl pretreatment > 1% H2SO4 pretreatment.

Insights into the effects of γ-irradiation on the microstructure, thermal stability and irradiation-derived degradation components of microcrystalline cellulose (MCC)

It has been demonstrated that radiation pretreatment can cause a significant breakdown of the stubborn cellulose structure, which will increase the accessibility of cellulose and enhance enzyme hydrolysis in bio-fuel processes. In this study, using microcrystalline cellulose (MCC) as a model substrate, the impacts of irradiation dose on the microstructure, thermal stability and irradiated-degradation components of cellulose under 60Co γ-irradiation (0–1400 kGy) was comprehensively investigated. FT-IR, EPR and NMR analyses show that irradiation destroys the glycosidic bond and inter- and intra-molecular hydrogen bond of cellulose, resulting in the generation of reductive carbonyl groups and free radicals. SEM, XRD and GPC analyses confirm that irradiation can damage the crystalline microstructure and surface morphology of MCC, which reduces its degree of polymerization from 183 045 kDa to 4413 kDa. TGA and DGA curves indicate that the activated energy (Ea) and thermal stability of treated MCC decrease with the increasing irradiation dose. Ion chromatography (IC) analysis demonstrates that there exist fermentation sugars such as glucose (10.73 mg g−1), xylose (1.58 mg g−1), arabinose (0.46 mg g−1), fructose (4.31 mg g−1), and cellobiose (1.90 mg g−1) as well as low amounts of glucuronic acid (0.35 mg g−1) and galacturonic acid (1.46 mg g−1) in the irradiation-derived degradation components. Therefore, the findings in this study suggest that γ-irradiation processing is an environment-friendly, promising and effective approach to treat lignocellulose biomass.