Brown Rot Fungi Reveal a New Approach for Biomass Conversion to Fuels and Chemicals

Brown rot fungi

(A) Brown rot fungi mushrooms, (B) SANS profiles, (C) SFG spectra of brown rot fungi–mediated cellulose deconstruction, and (D) AFM images of repolymerized lignin in brown rot cell walls. [(A) Wikimedia Commons, Zinnmann; (B) Authors; (C) and (D) From Goodell, B., et al. “Modification of the Nanostructure of Lignocellulose Cell walls via a Non-Enzymatic Lignocellulose Deconstruction System in Brown Rot Wood-Decay Fungi.” Biotechnol. Biofuels 10, 179 (2017). [DOI 10.1186/s13068-017-0865-2]. Reused under a Creative Commons license (CC BY 4.0, https://creativecommons.org/licenses/by/4.0/).]
A multimodal approach used in this study examined wood decay by the brown rot fungi, Gloeophyllum trabeum or Rhodonia placenta, that degrade wood using a chelator-mediated Fenton (CMF) reaction. Small-angle neutron scattering (SANS) showed changes in microfibril bundling and lignin structure during biomass breakdown. Complementary approaches, sum frequency generation (SFG) spectroscopy, X-ray diffraction, atomic force microscopy (AFM), and transmission electron microscopy (TEM) also contributed information on nanoscale structural changes in wood over time. Woods studied were southern yellow pine (Pinus spp.) and birch (Betula verrucosa Ehr.). The data support a degradation mechanism in which sugars released by non-enzymatic action diffuse from the cell wall,  facilitated by increasing the porosity of the cell walls. This is a paradigm shift in understanding the mechanism of brown rot fungal degradation.

Goodell, B., et al. “Modification of the Nanostructure of Lignocellulose Cell Walls via a Non-Enzymatic Lignocellulose Deconstruction System in Brown Rot Wood-Decay Fungi.” Biotechnol. Biofuels 10(1), 179 (2017). [DOI:10.1186/s13068-017-0865-2].

Instruments and Facilities Used: Small angle neutron scattering (SANS) – Bio-SANS at High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). Sum frequency generation (SFG) spectroscopy, broadband SFG system. Chelator-mediated Fenton treatments (CMF) and cellulase treatment. X-ray diffraction analysis (XRD) – PANalytical Empyrean diffractometer, The Netherlands, equipped with a Cu X-ray source. Attenuated total reflectance Fourier transform infrared analysis (ATR-FTIR): Nicolet 8700 FTIR Spectrometer (Thermo Scientific) equipped with a smart iTR diamond ATR unit, a KBr beam splitter, and a deuterated triglycine sulfate (DTGS) detector. Atomic force microscopy (AFM) of brown-rotted wood surfaces. Nanoscope IIIa AFM-Digital Instruments, Santa Barbara, California with three 5 µm scans. Transmission electron microscopy (TEM) – Philips CM12 TEM instrument (Philips, Eindhoven, The Netherlands); images recorded on Kodak 4489 negative film and the films subsequently scanned using an Epson Perfection Pro 750 film scanner.