Enhanced Softwood Cellulose Accessibility by H₃PO₄ Pretreatment: High Sugar Yield without Compromising Lignin Integrity

Journal Article · Mon Dec 23 00:00:00 EST 2019 · Industrial and Engineering Chemistry Research

DOI:https://doi.org/10.1021/acs.iecr.9b05873· OSTI ID:1581639

Hossain, Anwar ^[1]; Rahaman, Mohammad Shahinur ^[1]; Lee, David ^[2]; Phung, Thanh Khoa ^[1]; Canlas, Christian G. ^[3]; Simmons, Blake A.  ^[4]; Renneckar, Scott  ^[5]; Reynolds, William ^[6]; George, Anthe ^[7]; Tulaphol, Sarttrawut  ^[8]; Sathitsuksanoh, Noppadon  ^[1]

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1. Univ. of Louisville, KY (United States)
2. Joint BioEnergy Inst., Emeryville, CA (United States)
3. King Abdullah University of Science and Technology (KAUST), Thuwal (Saudi Arabia); Univ. of California, Berkeley, CA (United States)
4. Joint BioEnergy Inst., Emeryville, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
5. Univ. of British Columbia, Vancouver (Canada)
6. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
7. Joint BioEnergy Inst., Emeryville, CA (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
8. Univ. of Louisville, KY (United States); Univ. of Technology Thonburi, Bangkok (Thailand)

Softwood lignocellulose is a potential feedstock for the production of biofuels and bioproducts. However, the highly cross-linked nature of softwood lignocellulose restricts enzyme access to its sugars. Thus, harsh pretreatment conditions (180–280 °C) and/or high enzyme loading are required to unlock sugars. These requirements negatively affect the economic viability of softwoods in biorefineries. Here we show that H₃PO₄ pretreatment of pine and Douglas fir under a mild reaction temperature (50 °C) and atmospheric pressure enabled a high (~80%) glucan digestibility with low enzyme loading (5 filter paper units (FPU)/g glucan). The dissolution and regeneration of softwoods disrupted the hydrogen bonding between cellulose chains, thereby increasing the cellulose accessibility to cellulase (CAC) values by ~38-fold (from ~0.4 to 15 m²/g biomass). Examination of H₃PO₄-pretreated softwoods by cross-polarization/magic angle spin (CP/MAS), ¹³C- nuclear magnetic resonance (NMR), and Fourier-transform infrared spectroscopy (FTIR) revealed that breaking of the orderly hydrogen bonding of crystalline cellulose caused the increase in CAC (higher than 11 m²/g biomass), which, in turn, was responsible for the high glucan digestibility of pretreated softwoods. The H₃PO₄ pretreatment process was feedstock independent. Finally, 2D ¹³C–¹H heteronuclear single quantum coherence (HSQC) NMR showed that the lignin was depolymerized but not condensed; thus, the lignin can be available for producing high-value products.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC02-05CH11231; ECCS-1542174
• OSTI ID: 1581639
• Journal Information: Industrial and Engineering Chemistry Research, Vol. 59, Issue 2; ISSN 0888-5885
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
softwood
biomass
enzymes
accessibility
Lignocellulosic Biomass
Enzymatic hydrolysis