Iron incorporation both intra- and extra-cellularly improves the yield and saccharification of switchgrass (Panicum virgatum L.) biomass

Abstract

Background Pretreatments are commonly used to facilitate the deconstruction of lignocellulosic biomass to its component sugars and aromatics. Previously, we showed that iron ions can be used as co-catalysts to reduce the severity of dilute acid pretreatment of biomass. Transgenic iron-accumulating Arabidopsis and rice plants exhibited higher iron content in grains, increased biomass yield, and importantly, enhanced sugar release from the biomass. Results In this study, we used intracellular ferritin (FerIN) alone and in combination with an improved version of cell wall-bound carbohydrate-binding module fused iron-binding peptide (IBPex) specifically targeting switchgrass, a bioenergy crop species. The FerIN switchgrass improved by 15% in height and 65% in yield, whereas the FerIN/IBPex transgenics showed enhancement up to 30% in height and 115% in yield. The FerIN and FerIN/IBPex switchgrass had 27% and 51% higher in planta iron accumulation than the empty vector (EV) control, respectively, under normal growth conditions. Improved pretreatability was observed in FerIN switchgrass (~ 14% more glucose release than the EV), and the FerIN/IBPex plants showed further enhancement in glucose release up to 24%. Conclusions We conclude that this iron-accumulating strategy can be transferred from model plants and applied to bioenergy crops, such as switchgrass. The intra- and extra-cellular iron incorporation approach improves biomass pretreatability and digestibility, providing upgraded feedstocks for the production of biofuels and bioproducts.

Cell wall‐localized Bt protein endows rice high resistance to Lepidoptera pests

“…Before now, only a few studies reported accumulation of exogenous proteins in plant cell walls. Several fusion genes, including the sequence of signal peptide, carbohydrate binding domain and iron‐binding peptide, have been transformed to Arabidopsis , 52 rice 53 and switchgrass 54 to enhance the transition metal iron concentration on cell walls in order to facilitate the direct catalysis of cell wall deconstruction. Recently, we demonstrated that the red fluorescence protein mCherry could be accumulated on the cell walls of rice when it constituted a fusion protein with the extracellular secretion signal peptide and carbohydrate binding module too 22 .…”

Economic and Sustainability Impacts of Yield and Composition Variation in Bioenergy Crops: Switchgrass (Panicum virgatum L.)

“…Additional pretreatment steps may be required to overcome drought- or stress-induced plant recalcitrance . Finally, optimization of biochemical conversion is more likely to be cost-effective through using multiple avenues at once such as combining the use of less recalcitrant transgenic plants with pretreatment strategies. − …”

“… 14 Finally, optimization of biochemical conversion is more likely to be cost-effective through using multiple avenues at once such as combining the use of less recalcitrant transgenic plants with pretreatment strategies. 15 − 17 …”