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Restricting lignin and enhancing sugar deposition in secondary cell walls enhances monomeric sugar release after low temperature ionic liquid pretreatment.

Scullin C, Cruz AG, Chuang YD, Simmons BA, Loque D, Singh S - Biotechnol Biofuels (2015)

Bottom Line: Reducing the pretreatment temperature to 70 °C for 5 h resulted in a significant reduction in the peak sugar recovery obtained from the wild type to 16.2 g sugar per 100 g biomass, whereas the engineered lines with reduced lignin content exhibit a higher peak sugar recovery of 27.3 g sugar per 100 g biomass and 79 % glucose recoveries.The engineered Arabidopsis lines generate high sugar yields after pretreatment at 70 °C for 5 h and subsequent saccharification, while the wild type exhibits a reduced sugar yield relative to those obtained after pretreatment at 140 °C.Our results demonstrate that employing cell wall engineering efforts to decrease the recalcitrance of lignocellulosic biomass has the potential to drastically reduce the energy required for effective pretreatment.

View Article: PubMed Central - PubMed

Affiliation: Deconstruction Division, Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA USA ; Biological and Materials Science Center, Sandia National Laboratories, Livermore, CA USA.

ABSTRACT

Background: Lignocellulosic biomass has the potential to be a major source of renewable sugar for biofuel production. Before enzymatic hydrolysis, biomass must first undergo a pretreatment step in order to be more susceptible to saccharification and generate high yields of fermentable sugars. Lignin, a complex, interlinked, phenolic polymer, associates with secondary cell wall polysaccharides, rendering them less accessible to enzymatic hydrolysis. Herein, we describe the analysis of engineered Arabidopsis lines where lignin biosynthesis was repressed in fiber tissues but retained in the vessels, and polysaccharide deposition was enhanced in fiber cells with little to no apparent negative impact on growth phenotype.

Results: Engineered Arabidopsis plants were treated with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate 1-ethyl-3-methylimidazolium acetate ([C2C1im][OAc]) at 10 % wt biomass loading at either 70 °C for 5 h or 140 °C for 3 h. After pretreatment at 140 °C and subsequent saccharification, the relative peak sugar recovery of ~26.7 g sugar per 100 g biomass was not statistically different for the wild type than the peak recovery of ~25.8 g sugar per 100 g biomass for the engineered plants (84 versus 86 % glucose from the starting biomass). Reducing the pretreatment temperature to 70 °C for 5 h resulted in a significant reduction in the peak sugar recovery obtained from the wild type to 16.2 g sugar per 100 g biomass, whereas the engineered lines with reduced lignin content exhibit a higher peak sugar recovery of 27.3 g sugar per 100 g biomass and 79 % glucose recoveries.

Conclusions: The engineered Arabidopsis lines generate high sugar yields after pretreatment at 70 °C for 5 h and subsequent saccharification, while the wild type exhibits a reduced sugar yield relative to those obtained after pretreatment at 140 °C. Our results demonstrate that employing cell wall engineering efforts to decrease the recalcitrance of lignocellulosic biomass has the potential to drastically reduce the energy required for effective pretreatment.

No MeSH data available.


Compositional profile of the four Arabidopsis engineered lines (WT, LLL, LLHPL1, LLHPL2)
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Fig1: Compositional profile of the four Arabidopsis engineered lines (WT, LLL, LLHPL1, LLHPL2)

Mentions: Mature, senesced stems (corresponding to the main stems and side branches depleted of seeds and cauline leaves) from multiple plants of the WT, LLL, LLHPL1, and LLHPL2 Arabidopsis lines grown under the same conditions were collected and milled, and the chemical composition was quantified. As previously reported, all the lines (LLL, LLHPL1, and LLHPL2) harboring the pVND6::C4H construct, exhibit a significantly lower lignin content (12.9 to 14 %) compared to that of WT (19.1 %) and had no visible phenotypic differences (Table 1, Fig. 1) [21]. As expected, LLHPL1 shows an increase in the amount of both glucose 30.4 % and xylose 16.1 % present versus WT (26.1 and 11.4 % respectively). The LLHPL2 showed only a minor increase in xylose, 11.7 %, for the bulk composition and a significant decrease in the amount of glucose present, 22.1 %, where previously it was found to have a significant increase on a per plant scale [21]. Both the LLL and LLHPL2 engineered Arabidopsis lines exhibit a significant increase in acid soluble residue (ASR), while LLHPL1 had an increase in glucose with little change in ASR compared to WT (Table 1).Table 1


Restricting lignin and enhancing sugar deposition in secondary cell walls enhances monomeric sugar release after low temperature ionic liquid pretreatment.

Scullin C, Cruz AG, Chuang YD, Simmons BA, Loque D, Singh S - Biotechnol Biofuels (2015)

Compositional profile of the four Arabidopsis engineered lines (WT, LLL, LLHPL1, LLHPL2)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4496950&req=5

Fig1: Compositional profile of the four Arabidopsis engineered lines (WT, LLL, LLHPL1, LLHPL2)
Mentions: Mature, senesced stems (corresponding to the main stems and side branches depleted of seeds and cauline leaves) from multiple plants of the WT, LLL, LLHPL1, and LLHPL2 Arabidopsis lines grown under the same conditions were collected and milled, and the chemical composition was quantified. As previously reported, all the lines (LLL, LLHPL1, and LLHPL2) harboring the pVND6::C4H construct, exhibit a significantly lower lignin content (12.9 to 14 %) compared to that of WT (19.1 %) and had no visible phenotypic differences (Table 1, Fig. 1) [21]. As expected, LLHPL1 shows an increase in the amount of both glucose 30.4 % and xylose 16.1 % present versus WT (26.1 and 11.4 % respectively). The LLHPL2 showed only a minor increase in xylose, 11.7 %, for the bulk composition and a significant decrease in the amount of glucose present, 22.1 %, where previously it was found to have a significant increase on a per plant scale [21]. Both the LLL and LLHPL2 engineered Arabidopsis lines exhibit a significant increase in acid soluble residue (ASR), while LLHPL1 had an increase in glucose with little change in ASR compared to WT (Table 1).Table 1

Bottom Line: Reducing the pretreatment temperature to 70 °C for 5 h resulted in a significant reduction in the peak sugar recovery obtained from the wild type to 16.2 g sugar per 100 g biomass, whereas the engineered lines with reduced lignin content exhibit a higher peak sugar recovery of 27.3 g sugar per 100 g biomass and 79 % glucose recoveries.The engineered Arabidopsis lines generate high sugar yields after pretreatment at 70 °C for 5 h and subsequent saccharification, while the wild type exhibits a reduced sugar yield relative to those obtained after pretreatment at 140 °C.Our results demonstrate that employing cell wall engineering efforts to decrease the recalcitrance of lignocellulosic biomass has the potential to drastically reduce the energy required for effective pretreatment.

View Article: PubMed Central - PubMed

Affiliation: Deconstruction Division, Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA USA ; Biological and Materials Science Center, Sandia National Laboratories, Livermore, CA USA.

ABSTRACT

Background: Lignocellulosic biomass has the potential to be a major source of renewable sugar for biofuel production. Before enzymatic hydrolysis, biomass must first undergo a pretreatment step in order to be more susceptible to saccharification and generate high yields of fermentable sugars. Lignin, a complex, interlinked, phenolic polymer, associates with secondary cell wall polysaccharides, rendering them less accessible to enzymatic hydrolysis. Herein, we describe the analysis of engineered Arabidopsis lines where lignin biosynthesis was repressed in fiber tissues but retained in the vessels, and polysaccharide deposition was enhanced in fiber cells with little to no apparent negative impact on growth phenotype.

Results: Engineered Arabidopsis plants were treated with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate 1-ethyl-3-methylimidazolium acetate ([C2C1im][OAc]) at 10 % wt biomass loading at either 70 °C for 5 h or 140 °C for 3 h. After pretreatment at 140 °C and subsequent saccharification, the relative peak sugar recovery of ~26.7 g sugar per 100 g biomass was not statistically different for the wild type than the peak recovery of ~25.8 g sugar per 100 g biomass for the engineered plants (84 versus 86 % glucose from the starting biomass). Reducing the pretreatment temperature to 70 °C for 5 h resulted in a significant reduction in the peak sugar recovery obtained from the wild type to 16.2 g sugar per 100 g biomass, whereas the engineered lines with reduced lignin content exhibit a higher peak sugar recovery of 27.3 g sugar per 100 g biomass and 79 % glucose recoveries.

Conclusions: The engineered Arabidopsis lines generate high sugar yields after pretreatment at 70 °C for 5 h and subsequent saccharification, while the wild type exhibits a reduced sugar yield relative to those obtained after pretreatment at 140 °C. Our results demonstrate that employing cell wall engineering efforts to decrease the recalcitrance of lignocellulosic biomass has the potential to drastically reduce the energy required for effective pretreatment.

No MeSH data available.