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Bioprocess-Technological Potential of Irradiation-Based Fungal Pretreatment Platform Relevant to Lignocellulolytic Biocascade

Bak, Jin Seop
Applied biochemistry and biotechnology 2015 v.177 no.8 pp. 1654-1664
biomass, cell walls, ethanol, fermentation, fungi, irradiation, rice straw, saccharification, sugars
Lignocellulose-decaying fungal bioplatforms available are not commercially accessible and are limited to short-term use. In this study, those limitations were overcome by developing a platform using water-soaked rice straw (RS) biodegraded by irradiation-based fungal pretreatment (IBFP). This eco-friendly system increased the ability of RS to biodegrade and ferment without the generation of inhibitory compounds. When processed RS (i.e., with a water-soaking ratio of 81 % and irradiation dose of 80 kGy at 1 MeV and 0.12 mA) was pretreated with Dichomitus squalens for 9 days, the sugar yield was 58.5 % of the theoretical maximum. This sugar yield was comparable to that obtained with unirradiated RS for 15 days, which was 57.9 %. Furthermore, the ethanol concentration of 9.7 g L⁻¹ provided a yield of 58.1 %; the theoretical maximum and productivity at 0.40 g L⁻¹ h⁻¹ were determined after simultaneous saccharification and fermentation for 24 h. In addition, microscopic images revealed that IBFP induced predominant ultrastructural modifications to the surface of cell wall fibers. The peroxidative profiles for different biosystems were analyzed in order to understand substrate-specific biocascades based on the differences in biomass components. The activation level of core lignocellulolysis-related factors was analogous under the optimized conditions of each system.