Natural lignin modulators improve lignocellulose saccharification of field-grown sugarcane, soybean, and brachiaria

Abstract

Saccharification of lignocellulosic biomass might contribute to the bioethanol production, positively impacting energy security and sustainability. Lignin reduces polysaccharide saccharification and needs to be depolymerized and separated to improve fermentable sugar yield. Here, we report a substantial increase in lignocellulose saccharification after treating plants with the natural compounds: 3,4-(methylenedioxy)cinnamic acid (MDCA), a competitive inhibitor of 4-coenzyme A ligase (4CL); piperonylic acid (PIP), a quasi-irreversible inhibitor of cinnamyl 4-hydroxylase (C4H); and daidzin (DZN) a competitive inhibitor of coniferaldehyde dehydrogenase (CALDH). A single treatment with these inhibitors on different young developmental stages significantly increased lignocellulosic saccharification of crops at maturity stage. Field trial experiments with sugarcane (Saccharum spp), soybean (Glycine max), and brachiaria (Urochloa decumbens), showed that 12-month-old sugarcane bagasse increased saccharification up to 120%, 90-days-old soybean residues increased saccharification up to 36%, and 40-days-old brachiaria straw increased saccharification up to 21%. Treatments did not affect biomass productivity, lignin content or its monomeric composition. In contrast, anatomic assessment by UV microscopy revealed that MDCA affected tissue formation, increasing the lignification in fibers and vessels, but not in parenchyma. The tissue-specific and developmental persistent phenomena allowed a substantial increase in saccharification, while preserving the mechanical strength necessary for plant growth and development, suggesting that natural compounds are opportune for bioenergy applications.