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

Abstract

Since laccase acts specifically in lignin, the major contributor to biomass recalcitrance, this biocatalyst represents an important alternative to the pretreatment of lignocellulosic biomass. Therefore, this study investigates the laccase pretreatment and climate change effects on the hydrolytic performance of Panicum maximum. Through a Trop-T-FACE system, P. maximum grew under current (Control (C)) and future climate conditions: elevated temperature (2 °C more than the ambient canopy temperature) combined with elevated atmospheric CO2 concentration(600 μmol mol−1), name as eT+eC. Pretreatment using a laccase-rich crude extract from Lentinus sajor caju was optimized through statistical strategies, resulting in an increase in the sugar yield of P. maximum biomass (up to 57%) comparing to non-treated biomass and enabling hydrolysis at higher solid loading, achieving up to 26 g L−1. These increments are related to lignin removal (up to 46%) and lignin hydrophilization catalyzed by laccase. Results from SEM, CLSM, FTIR, and GC-MS supported the laccase-catalyzed lignin removal. Moreover, laccase mitigates climate effects, and no significant differences in hydrolytic potential were found between C and eT+eC groups. This study shows that crude laccase pretreatment is a potential and sustainable method for biorefinery solutions and helped establish P. maximum as a promising energy crop.

Assessment of Green Processes for Tomato Waste Biovalorization: Spotlight on the Innovative Pulsed Electric Field–Laccase Synergy for Enhanced Sugar and Phenol Extraction Yields

“…In fact, laccase has no direct impact on polysaccharide degradation, but the oxidative delignification induced by laccase promotes the extraction of certain carbohydrate fragments during the deformation of the lignin structure, which is directly linked to the lignin/polysaccharide bindings [31][32][33]. During the oxidation of lignin aromatic compounds by laccase, a partial or complete breakdown of hemicellulose is quite likely to occur, thereby contributing to a higher release of sugars [17,18,[32][33][34]. At the same time, a substantial decrease in polyphenols content was observed.…”

“…A mixture of commercial enzymes including 30% cellulase, 30% ß glucosidase, and 40% hemicellulase (Sigma Aldrich) was used for the hydrolysis of the biomass with a total initial activity of 50 U/g of substrate. The enzymatic mixture was deactivated at the end of the hydrolysis by heating at 100 °C for 10 min [17,18]. The centrifuged supernatant (10,000 rpm, 5 min) was stored at −20 °C for further use.…”

Improving Enzymatic Saccharification of Peach Palm (Bactris gasipaes) Wastes via Biological Pretreatment with Pleurotus ostreatus

“…Biological pre-treatment of lignocellulosic wastes using white-rot fungi has been used to promote especially delignification. Some examples are the biological pre-treatments of Eucalyptus grandis sawdust with several white-rot fungi [14], fruit residues with Pleurotus sp [19], and tropical forage grass (Panicum maximum) with Lentinus sajor-caju [23]. Laccase appears to be the most important enzyme involved in the delignification process [23][24][25].…”

Challenges of Biomass Utilization for Bioenergy in a Climate Change Scenario

“…As for CW polysaccharides, the content and composition of lignin were also found to be responsive to abiotic stress induced by climate change. Under CO 2 -enriched atmosphere (eTeC) or water stress (eTwS), the lignin content of Guinea grass leaves was 16 and 17% higher for eTeC and eTwS, respectively [ 117 , 139 ]. Temperature is recognized as a crucial factor controlling the lignification process of plant tissues [ 140 ].…”

“…Nonetheless, this process alters cell wall structure, chemical composition, and association among its polymers, with the potential of influencing the climate change effect. Although warming is shown to have a positive effect on Guinea grass hydrolysis yields, the pretreatment using laccase or hydrothermal methods mitigates the climate change effects on the grass hydrolysis potential since no significant differences were found between groups grown under currently ambient conditions and eTeC treatments [ 133 , 139 ]. Therefore, integrating the effects of pretreatment and climate changes in lignocellulosic biomass must be investigated for potential biorefinery feedstocks.…”