Climate change affects cell wall structure and hydrolytic performance of a tropical forage grass as an energy crop

Abstract

Forage grasses, such as Panicum maximum, are important alternatives of lignocellulosic biomass for bioethanol production. Thus, this study investigates whether future climate conditions could influence P. maximum cell wall structure and hydrolytic performance. A combined temperature-free air controlled and a free-air carbon dioxide enrichment (Trop-T-FACE) facility was used to investigated 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. Warming reduced starch content and crystallinity index (CI) of cellulose while increased cellulose content. The fluorescent protein-tagged carbohydrate-binding modules analysis demonstrated that warming led to improvement in the 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 affect its use in biorefineries. Therefore, this work provides important information from an ecological and economic point of view, and might assist in the selection of tropical forage grasses efficiently adapted to climate changes with positive effect on bioenergy production.

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

“…Concerning the differences found between climate conditions, for non-treated P. maximum biomass Control (C) group had significantly (p < 0.05) lower sugar yields compared to elevated temperature + elevated CO 2 (eT+eC) for all conditions performed in this study (Figures 4-7). The possible explanations for these differences are described in detail in a previous study from our research group, in which similar hydrolysis results were found [38]. However, no differences were found between C and eT+eC groups after crude laccase pretreatment, suggesting that crude laccase pretreatment extensively modifies P. maximum fibers.…”

“…Also, the relative increase in sugar yields between pretreated and non-treated biomass showed to be higher for the C group in relation to eT+eC substrates (Figures 4-7). This result indicates that laccase action was more advantageous to the C group, probably because this climate condition has a more recalcitrant structure than eT+eC for raw biomass [38]. Therefore, laccase pretreatment assisted in overcome these differences approximating the bioenergetic potential of both climate conditions.…”