Naturally p-Hydroxybenzoylated Lignins in Palms

Abstract

The industrial production of palm oil concurrently generates a substantial amount of empty fruit bunch (EFB) fibers that could be used as a feedstock in a lignocellulosebased biorefinery. Lignin byproducts generated by this process may offer opportunities for the isolation of value-added products, such as p-hydroxybenzoate (pBz), to help offset operating costs. Analysis of the EFB lignin by nuclear magnetic resonance (NMR) spectroscopy clearly revealed the presence of bound acetate and pBz, with saponification revealing that 1.1 wt% of the EFB was pBz; with a lignin content of 22.7 %, 4.8 % of the lignin is pBz that can be obtained as a pure component for use as a chemical feedstock. Analysis of EFB lignin by NMR and derivatization followed by reductive cleavage (DFRC) showed that pBz selectively

Highly Decorated Lignins in Leaf Tissues of the Canary Island Date Palm Phoenix canariensis

“…Incorporation of ML-conj into the lignin was determined using the ethercleaving ester-retaining DFRC method established previously for ML-pCA, ML-FA, and ML-pBA conjugates Ralph, 1999, 2014;Petrik et al, 2014;Wilkerson et al, 2014;Lu et al, 2015). The DFRC protocol used here was as follows.…”

“…The classic G-G b-O-4 model compound guaiacylglycerol-b-guaiacyl ether (Lundquist and Remmerth, 1975), lignin dimer in Figure 4, was selected to represent compounds of similar hydrodynamic volume as a compound formed from the radical coupling of two monolignols. The G-G model compound was prepared following the synthesis described previously (Lu et al, 2015). Larger hydrodynamic volume representatives, lignin tetramer, lignin trimer, and lignin dimer structures in Figure 4, were chosen based on their ease of synthesis and such that they most closely represent linear b-ether chains.…”

“…sodium benzoate and parabens [which are a family of p-hydroxybenzoate esters]), it is believed that the wallbound phenolic acids play a role in the plant's defense system. Although no evidence was found for any ligninassociated pCA in African oil palm (Elaeis guineensis) empty fruit bunches (Lu et al, 2015), it was reported to be in leaf-base fiber tissues (Sun et al, 2001). This provided early evidence in palms suggesting organ-and/ or tissue-dependent distribution of lignins derived, in part, from ML-conj.…”

“…The ML-Ac conjugates were subsequently shown in kenaf to be formed prior to lignification Ralph, 2002, 2008). Much later, the monolignol p-hydroxybenzoates (ML-pBA) were authenticated as members of the lignin monomer pool (Lu et al, 2015). Most recently, some of the acyltransferase enzymes that form ML-conj were identified and their functions confirmed in planta, particularly for ML-pCA (Withers et al, 2012;Bartley et al, 2013;Marita et al, 2014;Petrik et al, 2014;Sibout et al, 2016) and the recently discovered monolignol ferulates (ML-FA; Wilkerson et al, 2014;Karlen et al, 2016).…”

Relationships between Biomass Composition and Liquid Products Formed via Pyrolysis

“…Lignin units undergo oxidative coupling in the cell wall to form many types of dimers, including β-O-4, β-5, β-β, 5-5, 5-O-4, and β-1, leaving other atoms free to further polymerize, which significantly increases the structural heterogeneity of lignin. Lignin units can also be esterified with p-coumaryl, p-hydroxybenzoyl, and acetyl groups, primarily at the γ position of terminal units (Petrik et al, 2014;Lu et al, 2015). Lignin compositions and the acylation groups vary among plant clades (Boerjan et al, 2003).…”