Naturally p-Hydroxybenzoylated Lignins in Palms

Fachuang Lu,Sally A Ralph,Hoon Kim,Steven D Karlen,Henry Sabarez,Sarani Zakaria,Run-Cang Sun,Ken-Ichi Kuroda,Philip J Harris,John Ralph,Stefan Hill,Shawn D Mansfield,Gerardo Jimenez-Monteon,Curtis G Wilkerson,Mary Ann Augustin,Tanoj Singh,Matt Regner,Raymond Mawson,Wout Boerjan

doi:10.1007/s12155-015-9583-4

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 lignocellulose-based 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 acylates the γ-hydroxyl group of S units. This selectivity suggests that pBz, analogously with acetate in kenaf, p-coumarate in grasses, and ferulate in a transgenic poplar augmented with a feruloyl-CoA monolignol transferase (FMT), is incorporated into the growing lignin chain via its γ-p-hydroxybenzoylated monolignol conjugate. Involvement of such conjugates in palm lignification is proven by the observation of novel p-hydroxybenzoylated non-resinol β–β-coupled units in the lignins. Together, the data implicate the existence of p-hydroxybenzoyl-CoA:monolignol transferases that are involved in lignification in the various willows (Salix spp.), poplars and aspen (Populus spp., family Salicaceae), and palms (family Arecaceae) that have p-hydroxybenzoylated lignins. Even without enhancing the levels by breeding or genetic engineering, current palm oil EFB ‘wastes’ should be able to generate a sizeable stream of p-hydroxybenzoic acid that offers opportunities for the development of value-added products derived from the oil palm industry.

Highlights

In order for a lignocellulose biorefinery to function as an economically viable enterprise, it must be developed to yield value-added coproducts in the process [1, 2]
The production of palm oil generates a substantial amount of empty fruit bunch (EFB) fibers that can be readily processed into sugars for biofuels production and a mixture of unfermentable components including lignin
Björkman milled wood lignins (MWLs) were prepared from the oil palm (Elaeis guineensis) EFB fibers, fronds, and trunk fractions; the EFBs had already been shown to be rich in p-hydroxybenzoates [34]

Summary

Introduction

In order for a lignocellulose biorefinery to function as an economically viable enterprise, it must be developed to yield value-added coproducts in the process [1, 2]. In 2013 Malaysia, the second largest oil palm producer after Indonesia, produced over 19 million tons of palm oil on a total plantation area of over 5 million ha, which generated an estimated 70–80 million tons of biomass, mostly from oil palm EFB [4]. This biomass, which is a high-quality lignocellulosic fiber, has not been fully utilized commercially and is a largely untapped resource, research in the biorefinery area has attempted to provide high value-added products via liquefaction [5], solvolysis [6] and pyrolysis [7]

Methods

Results

Conclusion