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1. Estrogenic activity of lignin-derivable alternatives to bisphenol A assessed via molecular docking simulations

   https://doi.org/10.1039/d1ra02170b  

   Amitrano, Alice; Mahajan, Jignesh S.; Korley, LaShanda T.; Epps, Thomas H. (June 2021, RSC Advances)

   null (Ed.)

   Lignin-derivable bisphenols are potential alternatives to bisphenol A (BPA), a suspected endocrine disruptor; however, a greater understanding of structure–activity relationships (SARs) associated with such lignin-derivable building blocks is necessary to move replacement efforts forward. This study focuses on the prediction of bisphenol estrogenic activity (EA) to inform the design of potentially safer BPA alternatives. To achieve this goal, the binding affinities to estrogen receptor alpha (ERα) of lignin-derivable bisphenols were calculated via molecular docking simulations and correlated to median effective concentration (EC 50 ) values using an empirical correlation curve created from known EC 50 values and binding affinities of commercial (bis)phenols. Based on the correlation curve, lignin-derivable bisphenols with binding affinities weaker than ∼−6.0 kcal mol −1 were expected to exhibit no EA, and further analysis suggested that having two methoxy groups on an aromatic ring of the bio-derivable bisphenol was largely responsible for the reduction in binding to ERα. Such dimethoxy aromatics are readily sourced from the depolymerization of hardwood biomass. Additionally, bulkier substituents on the bridging carbon of lignin-bisphenols, like diethyl or dimethoxy, were shown to weaken binding to ERα. And, as the bio-derivable aromatics maintain major structural similarities to BPA, the resultant polymeric materials should possess comparable/equivalent thermal ( e.g. , glass transition temperatures, thermal decomposition temperatures) and mechanical ( e.g. , tensile strength, modulus) properties to those of polymers derived from BPA. Hence, the SARs established in this work can facilitate the development of sustainable polymers that maintain the performance of existing BPA-based materials while simultaneously reducing estrogenic potential. 

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2. Unlocking Circularity Through the Chemical Recycling and Upcycling of Lignin-Derivable Polymethacrylates

   https://doi.org/10.1021/acs.macromol.3c01985  

   Christoff-Tempesta, Ty; O’Dea, Robert M; Epps, Thomas H (December 2023, Macromolecules)

   The synthesis of polymers from lignin-derivable compounds can replace petrochemical building blocks with a renewable feedstock. However, the end-of-life management of bioderivable, nonbiodegradable polymers remains an outstanding challenge. Herein, the chemical recycling and upcycling of two higher-glass-transition temperature (>100 °C), lignin-derivable polymethacrylates, poly(syringyl methacrylate) (PSM) and poly(guaiacyl methacrylate) (PGM), is reported. Neat PSM and PGM were thermally depolymerized to quantitative conversions, producing their constituent monomers at high yields and purity. The deconstruction atmosphere influenced the depolymerization reaction order, and depolymerization was thermodynamically favored in air over N2. Further, monomer bulkiness and volatility impacted depolymerization activation energies. Notably, bulk depolymerization of PSM and PGM was performed without solvent or catalyst to high polymer conversions (89–90 wt %) and monomer yields (86–90 mol %) without byproduct formation. The resultant monomers were then upcycled to narrow-dispersity polymers and phase-separated block polymers. The findings herein offer a pathway to material circularity for higher-performance, lignin-derivable polymethacrylates. 

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3. Engineering lignin-derivable diacrylate networks with tunable architecture and mechanics

   https://doi.org/10.1039/D4MA00159A  

   Wong, Yu-Tai; Korley, LaShanda_T J (July 2024, Materials Advances)

   Thermomechanical properties are tuned by varying diacrylate content and size in lignin-derivable networks, highlighting the design of processable, fully renewable, and performance-driven (meth)acrylate networks using network engineering approaches. 

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4. Lignin-derivable alternatives to petroleum-derived non-isocyanate polyurethane thermosets with enhanced toughness

   https://doi.org/10.1039/d2ma00895e  

   Mhatre, Sampanna V.; Mahajan, Jignesh S.; Epps, Thomas H.; Korley, LaShanda T. (January 2023, Materials Advances)

   The structural similarities between lignin-derivable bisguaiacols and petroleum-derived bisphenol A/F (BPA/BPF) suggest that bisguaiacols could be ideal biobased alternatives to BPA/BPF in non-isocyanate polyurethane (NIPU) thermosets. Herein, bisguaiacol/bisphenol-derived cyclic carbonates with variations in methoxy content and bridging-carbon substitution were cured with two triamines of different chain lengths, and the impact of these differences on the thermomechanical properties of NIPU networks was examined. The methoxy groups present in the lignin-derivable cyclic carbonates led to thermosets with significantly improved toughness (∼49–59 MJ m −3 ) and elongation at break ( ε b ∼195–278%) vs. the BPA/BPF-based benchmarks (toughness ∼ 26–35 MJ m −3 , ε b ∼ 86–166%). Furthermore, the addition of dimethyl substitution on the bridging carbon resulted in increased yield strength ( σ y ) – from ∼28 MPa for networks with unsubstituted bridging carbons to ∼45 MPa for the dimethyl-substituted materials. These enhancements to mechanical properties were achieved while retaining essential thermoset properties, such as application-relevant moduli and thermal stabilities. Finally, the triamine crosslinkers provided substantial tunability of thermomechanical properties and produced NIPUs that ranged from rigid materials with a high yield strength ( σ y ∼ 65–88 MPa) to flexible and tough networks. Overall, the structure-property relationships presented highlight a promising framework for the design of versatile, bio-derivable, NIPU thermosets. 

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5. High Enzyme Promiscuity in Lignin Degradation Mechanisms in Rhodopseudomonas palustris CGA009

   https://doi.org/10.1101/2025.02.15.638337  

   Kathol, Mark; Chowdhury, Niaz Bahar; Immethun, Cheryl; Alsiyabi, Adil; Morris, Dianna; Naldrett, Michael J; Saha, Rajib (February 2025, bioRxiv)

   Abstract Lignin is a universal waste product of the agricultural industry and is currently seen as a potential feedstock for more sustainable manufacturing. While it is the second most abundant biopolymer in the world, most of it is currently burned as it is a very recalcitrant material. Many recent studies, however, have demonstrated the viability of biocatalysis to improve the value of this feedstock and convert it into more useful chemicals, such as polyhydroxybutyrate, and clean fuels like hydrogen and n-butanol.Rhodopseudomonas palustrisis a gram-negative bacterium which demonstrates a plethora of desirable metabolic capabilities, including aromatic catabolism useful for lignin degradation. This study uses a multi-omics approach, including the first usage of CRISPRi inR. palustris, to investigate the lignin consumption mechanisms ofR. palustris, the essentiality of redox homeostasis to lignin consumption, elucidate a potential lignin catabolic superpathway, and enable more economically viable sustainable lignin valorization processes. 

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