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Perennial grasses, such as Panicum maximum, are important alternatives to dedicated energy crops for bioethanol production. This study investigates whether future climate conditions could influence P. maximum cell‐wall structure and hydrolytic performance. To analyze interactions with environmental factors in field conditions, a combined Free‐air Temperature and CO2 Controlled Enhancement (Trop‐T‐FACE) facility was used to investigate the isolated and combined effect of elevated atmospheric CO2 concentration (eC) (600 μmol.mol−1) and elevated temperature (eT) by 2 °C more than the ambient temperature, on cell‐wall composition, cellulose crystallinity, accessibility, and hydrolysis yields. The elevated temperature treatments (eT and eT + eC) exhibited the most pronounced effects on the P. maximum cell wall. Warming reduced the starch content and the crystallinity index (CI) of cellulose and increased the cellulose content. Fluorescent protein‐tagged carbohydrate‐binding modules analysis demonstrated that warming improved total cellulose surface exposure/accessibility in eT and eT + eC by 181% and 132%, respectively. Consequently, glucan conversion yields were improved by 7.07% and 5.37%, showing that warming led to lower recalcitrance in P. maximum biomass, which positively affects its use in biorefineries. This work therefore provides important information from an ecological and economic point of view, allowing us to understand the mitigation process applied by this forage grass under future climate conditions. It might assist in selecting tropical forage grasses that are efficiently adapted to climate change, with a positive effect on bioenergy production. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd [ABSTRACT FROM AUTHOR]

Summary: Feruloylation of arabinoxylan (AX) in grass cell walls is a key determinant of recalcitrance to enzyme attack, making it a target for improvement of grass crops, and of interest in grass evolution. Definitive evidence on the genes responsible is lacking so we studied a candidate gene that we identified within the BAHD acyl‐CoA transferase family. We used RNA interference (RNAi) silencing of orthologs in the model grasses Setaria viridis (SvBAHD01) and Brachypodium distachyon (BdBAHD01) and determined effects on AX feruloylation. Silencing of SvBAHD01 in Setaria resulted in a c. 60% decrease in AX feruloylation in stems consistently across four generations. Silencing of BdBAHD01 in Brachypodium stems decreased feruloylation much less, possibly due to higher expression of functionally redundant genes. Setaria SvBAHD01 RNAi plants showed: no decrease in total lignin, approximately doubled arabinose acylated by p‐coumarate, changes in two‐dimensional NMR spectra of unfractionated cell walls consistent with biochemical estimates, no effect on total biomass production and an increase in biomass saccharification efficiency of 40–60%. We provide the first strong evidence for a key role of the BAHD01 gene in AX feruloylation and demonstrate that it is a promising target for improvement of grass crops for biofuel, biorefining and animal nutrition applications. [ABSTRACT FROM AUTHOR]

Feruloyl esterase is a subclass of carboxylic acid esterases with the capacity to release ferulic acid and other cinnamic acids from plant cell walls and synthetic substrates. Feruloyl esterases act synergistically with xylanases removing ferulic acid residues esterified to arabinoxylans. Feruloyl esterase type D from Aspergillus clavatus (AcFAE) was expressed in Escherichia coli, purified, and applied with a commercial xylanase consortium (Novozymes) for hydrolysis of sugarcane bagasse. Feruloyl esterase plus xylanase increased 5.13-fold the releasing of ferulic acid from sugarcane bagasse. Removal of only 7.7% of ferulic acid content by AcFAE increased 97.3% the sugarcane bagasse hydrolysis by xylanase. These data support the use of AcFAE as an interesting adjuvant enzyme to improve lignocellulose digestion and biotechnological tool for biorefineries. [ABSTRACT FROM AUTHOR]

Grass cell walls have hydroxycinnamic acids attached to arabinosyl residues of arabinoxylan (AX), and certain BAHD acyltransferases are involved in their addition. In this study, we characterized one of these BAHD genes in the cell wall of the model grass Setaria viridis. RNAi silenced lines of S. viridis (SvBAHD05) presented a decrease of up to 42% of ester-linked p-coumarate (pCA) and 50% of pCA-arabinofuranosyl, across three generations. Biomass from SvBAHD05 silenced plants exhibited up to 32% increase in biomass saccharification after acid pre-treatment, with no change in total lignin. Molecular dynamics simulations suggested that SvBAHD05 is a p-coumaroyl coenzyme A transferase (PAT) mainly involved in the addition of pCA to the arabinofuranosyl residues of AX in Setaria. Thus, our results provide evidence of p-coumaroylation of AX promoted by SvBAHD05 acyltransferase in the cell wall of the model grass S. viridis. Furthermore, SvBAHD05 is a promising biotechnological target to engineer crops for improved biomass digestibility for biofuels, biorefineries and animal feeding., (© 2020 Society for Experimental Biology and John Wiley & Sons Ltd.)