From Lignocellulosic Biomasses to Advanced Biopolymers in Just One Step

Developing economically sustainable processes for lignin valorization remains a significant challenge. Recently, a new paradigm known as “lignin-first” has emerged, focusing on lignin fractionation through biopolymer solvolysis followed by reductive stabilization to prevent biopolymer condensation. ^[1] Our research centers on ethanosolv processes aimed at achieving high retention of β-O-4 linkages in lignin fractions, using endocarps as feedstocks. Particularly, pistachio dried shells have shown promising results.^[2] By optimizing biomass pre-treatment and utilizing microwave-assisted extraction, we achieved a delignification yield exceeding 70%, with lignin fractions primarily composed of S units and retaining approximately 70% β-O-4 linkages. However, the process duration, requiring 10 hours at 80°C, is a drawback. To enhance economic sustainability, we explored a single-step process that simultaneously extracts and functionalizes lignin. This approach eliminates the need for post-processing and enables lignin functionalization with various species such as redox-active species, chromophores, or antioxidants, thus streamlining the process and reducing costs.<br/>Our findings demonstrate that using pistachio shells as feedstock in an optimized ethanosolv process can yield high-quality lignin fractions with significant retention of β-O-4 linkages. While the process duration remains a challenge, the development of a single-step extraction and functionalization method offers a promising path toward more economically viable lignin valorization, transforming lignin from a waste to a versatile material. This integrated approach not only simplifies the process but also adds value to lignin by enabling its functionalization for various applications, potentially leading to broader industrial adoption and enhanced sustainability in biomass utilization.<br/><br/>[1] T. I. Korányi, B. Fridrich, A. Pineda, K. Barta, <i>Molecules</i> <b>2020</b>, <i>25</i>, 2815.<br/>[2] D. Blasi, D. Mesto, P. Cotugno, C. D. Calvano, M. Lo Presti, G. M. Farinola, <i>Green Chem. Lett. Rev.</i> <b>2022</b>, <i>15</i>, 893–902.