Enzymatic Delignification of Biomass for Enhanced Fermentable Sugars Production

Abstract

The United Arab Emirates (UAE) has more than 40 million palm trees producing approximately 15 kg of waste fronds per tree. These fronds contain a large portion of polysaccharides, which can be hydrolyzed to simple fermentable sugars. Seaweed consists of macroalgae containing high portions of polysaccharides, which are also abundantly found on the coasts of UAE. The effectiveness of lignin to degrade enzymes for the pretreatment of biomass from palm trees fronds and indigenous seaweed (prior to enzymatic hydrolysis) has been investigated and compared to conventional chemical treatment. By treating with laccase, up to 9 and 24 % additional lignin was removed from palm fronds and seaweed, respectively. The performance of laccase was enhanced by using an ionic liquid, and a sugar yield of 12.6 % was achieved after treatment with laccase for only 1 hour. The proposed approach provides a promising simplification to the overall bioethanol production from biomass waste available globally in abundance, and in the UAE in particular.

Enzymatic Pretreatment with Laccases from Lentinus sajor-caju Induces Structural Modification in Lignin and Enhances the Digestibility of Tropical Forage Grass (Panicum maximum) Grown under Future Climate Conditions

“…The lignin removal obtained in this study is higher than those reported using commercial laccases or in laccase association with other pretreatment methods (Table 4). Al-Zuhair et al, (2015) [31] stated 9% of delignification with commercial Trametes versicolor laccase using HBT (hydroxybenzotriazole) as mediator. Rencoret et al, (2019) described 24% of lignin removal from Paulownia fortune after laccase-mediated pretreatment combined with alkaline extraction with NaOH [32], while Gutiérrez et al, (2012) reported up to 32% reduction in lignin content for Elephant grass applying the same combine pretreatment [33].…”

Simultaneous Enzymatic Cellulose Hydrolysis and Product Separation in a Radial-Flow Membrane Bioreactor

“…The peaks at 16° and 23° reflect crystalline cellulose type I, while cellulose type II is presented at 20°. The intensity of those peaks increased in both full-pretreatment and lignin-removed DSs biomass, which indicates a higher crystallinity degree in the structure of the treated fibers due to the removal of lignin [ 25 ]. A similar increase in the intensity of peaks that represent crystalline cellulose was also observed with DSs from Phoenix dactylifera L. after lignin and hemicellulose removal [ 26 ].…”

Recent Developments in the Delignification and Exploitation of Grass Lignocellulosic Biomass

“…158 Al-Zuhair et al investigated the enzymatic delignification of seaweed biomass (a mix of Chaetomorpha and Cladophora species), carried out using TvL, HBT, and [EMIM][OAc] obtaining a delignification degree up to 27%. 162 Rezaei et al reported the use of LC from the halophilic bacterium Aquisalibacillus elongatus in the presence of [BMIM]-[PF 6 ] (1-butyl-3-methylimidazolium hexafluorophosphate) to delignify sugar beet pulp, obtaining a delignification yield of 78.4% after 24 h. 163 The same enzyme was also tested in the same conditions in [BMIM][PF 6 ] to remove lignin from peanut shell, obtaining a lignin removal of 87% after 24 h. 164 Deep Eutectic Solvents. Deep eutectic solvents (DESs) are a new class of green solvents composed of a hydrogen bond acceptor (HBA, usually a quaternary ammonium salt) and a hydrogen bond donor (HBD) such as glycerol, succinic acid, etc.…”

“…They obtained a final lignin content of about 8.5 wt %, compared to the initial 24.0 wt % of untreated OPFB . Al-Zuhair et al investigated the enzymatic delignification of seaweed biomass (a mix of Chaetomorpha and Cladophora species), carried out using TvL, HBT, and [EMIM]­[OAc] obtaining a delignification degree up to 27% . Rezaei et al reported the use of LC from the halophilic bacterium Aquisalibacillus elongatus in the presence of [BMIM]­[PF 6 ] (1-butyl-3-methylimidazolium hexafluorophosphate) to delignify sugar beet pulp, obtaining a delignification yield of 78.4% after 24 h .…”