| 1. |
- Bhalla, Aditya, et al.
(författare)
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Engineered Lignin in Poplar Biomass Facilitates Cu-Catalyzed Alkaline-Oxidative
- 2018
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 6:3, s. 2932-2941
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Tidskriftsartikel (refereegranskat)abstract
- Both untransformed poplar and genetically modified “zip-lignin” poplar, in which additional ester bonds were introduced into the lignin backbone, were subjected to mild alkaline and copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment. Our hypothesis was that the lignin in zip-lignin poplar would be removed more easily than lignin in untransformed poplar during this alkaline pretreatment, resulting in higher sugar yields following enzymatic hydrolysis. We observed improved glucose and xylose hydrolysis yields for zip-lignin poplar compared to untransformed poplar following both alkaline-only pretreatment (56% glucose yield for untransformed poplar compared to 67% for zip-lignin poplar) and Cu-AHP pretreatment (77% glucose yield for untransformed poplar compared to 85% for zip-lignin poplar). Compositional analysis, glycome profiling, and microscopy all supported the notion that the ester linkages increase delignification and improve sugar yields. Essentially no differences were noted in the molecular weight distributions of solubilized lignins between the zip-lignin poplar and the control line. Significantly, when zip-lignin poplar was utilized as the feedstock, hydrogen peroxide, catalyst, and enzyme loadings could all be substantially reduced while maintaining high sugar yields.
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| 2. |
- Crowe, Jacob D., et al.
(författare)
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Alkaline and Alkaline-Oxidative Pretreatment and Hydrolysis of Herbaceous Biomass for Growth of Oleaginous Microbes
- 2019
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Ingår i: Microbial Lipid Production. - New York, NY : Springer Nature. ; , s. 173-182
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter describes methods for generation of hydrolysates amenable to conversion to microbial lipids from herbaceous lignocellulosic biomass utilizing either mild alkali pretreatment with NaOH or alkaline hydrogen peroxide pretreatment with NaOH and H2O2. This pretreatment is followed by enzymatic hydrolysis of the plant cell wall polysaccharides to yield hydrolysates. These hydrolysates are composed primarily of the monosaccharides glucose and xylose as well as acetate and phenolic monomers that may all serve as a source of renewable carbon to produce microbial lipids. Application of these mild pretreatment conditions minimizes the generation of inhibitors, enabling microbial cultivations to often be performed without the need for detoxification.
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| 3. |
- Li, Muyang, et al.
(författare)
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Cell-wall properties contributing to improved deconstruction by alkaline pre-treatment and enzymatic hydrolysis in diverse maize (Zea mays L.) lines
- 2015
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Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 66:14, s. 4305-4315
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Tidskriftsartikel (refereegranskat)abstract
- A maize (Zea mays L. subsp. mays) diversity panel consisting of 26 maize lines exhibiting a wide range of cell-wall properties and responses to hydrolysis by cellulolytic enzymes was employed to investigate the relationship between cell-wall properties, cell-wall responses to mild NaOH pre-treatment, and enzymatic hydrolysis yields. Enzymatic hydrolysis of the cellulose in the untreated maize was found to be positively correlated with the water retention value, which is a measure of cell-wall susceptibility to swelling. It was also positively correlated with the lignin syringyl/guaiacyl ratio and negatively correlated with the initial cell-wall lignin, xylan, acetate, and p-coumaric acid (pCA) content, as well as pCA released from the cell wall by pre-treatment. The hydrolysis yield following pre-treatment exhibited statistically significant negative correlations to the lignin content after pre-treatment and positive correlations to the solubilized ferulic acid and pCA. Several unanticipated results were observed, including a positive correlation between initial lignin and acetate content, lack of correlation between acetate content and initial xylan content, and negative correlation between each of these three variables to the hydrolysis yields for untreated maize. Another surprising result was that pCA release was negatively correlated with hydrolysis yields for untreated maize and, along with ferulic acid release, was positively correlated with the pre-treated maize hydrolysis yields. This indicates that these properties that may negatively contribute to the recalcitrance in untreated cell walls may positively contribute to their deconstruction by alkaline pre-treatment.
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| 4. |
- Li, Muyang, et al.
(författare)
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Identification of features associated with plant cell wall recalcitrance to pretreatment by alkaline hydrogen peroxide in diverse bioenergy feedstocks using glycome profiling
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:33, s. 17282-17292
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Tidskriftsartikel (refereegranskat)abstract
- A woody dicot (hybrid poplar), an herbaceous dicot (goldenrod), and a graminaceous monocot (corn stover) were subjected to alkaline hydrogen peroxide (AHP) pretreatment and subsequent enzymatic hydrolysis in order to assess how taxonomically and structurally diverse biomass feedstocks respond to a mild alkaline oxidative pretreatment and how differing features of the cell wall matrix contribute to its recalcitrance. Using glycome profiling, we determined changes in the extractability of non-cellulosic glucans following pretreatment by screening extracts of the pretreated walls with a panel of 155 cell wall glycan-directed monoclonal antibodies to determine differences in the abundance and distribution of non-cellulosic glycan epitopes in these extracts and assess pretreatment-induced changes in the structural integrity of the cell wall. Two taxonomically-dependent outcomes of pretreatment were identified that both improved the subsequent enzymatic hydrolysis yields but differed in their impacts on cell wall structural integrity. Specifically, it was revealed that goldenrod walls exhibited decreases in all classes of alkali-extractable glycans indicating their solubilization during pretreatment, which was accompanied by an improvement in the subsequent extractability of the remaining cell wall glycans. The corn stover walls did not show the same decreases in glycan abundance in extracts following pretreatment, but rather mild increases in all classes of cell wall glycans, indicating overall weaker associations between cell wall polymers and improved extractability. The hybrid poplar walls were relatively unaffected by pretreatment in terms of composition, enzymatic hydrolysis, and the extractability of cell wall glycans due presumably to their higher lignin content and denser vascular structure.
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| 5. |
- Li, Muyang, et al.
(författare)
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Physical fractionation of sweet sorghum and forage/energy sorghum for optimal processing in a biorefinery
- 2018
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Ingår i: Industrial crops and products (Print). - : Elsevier. - 0926-6690 .- 1872-633X. ; 124, s. 607-616
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Tidskriftsartikel (refereegranskat)abstract
- Sorghum offers enormous potential as a feedstock for the production of fuels and chemicals from both water-extractable sugars and the cell wall biopolymers, while its within-plant structural and compositional heterogeneity may allow for physical fractionations to tailor feedstock properties to a biorefining process. In this study, the stem internodes of two sorghum (Sorghum bicolor L. Moench) genotypes, a sweet sorghum (‘Della’) and a forage/energy sorghum (‘TX08001’), were first subjected to fractionation by manual classification by stem anatomy and internode proximity to the ground to yield 18 fractions. These fractions exhibited substantial differences in cell wall morphology, composition, and recalcitrance to mild alkaline pretreatment and enzymatic hydrolysis. While the sweet sorghum cultivar held nearly 70% more water-extractable sugar (sucrose, glucose, fructose, starch) in the stems than the forage/energy sorghum hybrid, both cultivars exhibited comparable diversity of composition and these compositions were remarkably similar in similar tissues and stem regions between the two cultivars. The fractions isolated from the pith parenchyma were the least recalcitrant to mild alkaline pretreatment and enzymatic hydrolysis and contained less lignin than fractions isolated from the epidermis, outer and inner rind, and internal vascular bundles. The pith samples isolated from the lowest region of the stem from both cultivars exhibited near-theoretical sugar hydrolysis yields when no pretreatment was employed and exhibited the lowest lignin contents of any of the fractions. Next, a physical fractionation approach approximating a commercial “de-pithing” process utilizing wet disintegration and sieving was applied to the forage/energy sorghum. A pith-rich fraction representing approximately 20% of the extractives-free mass of the stem could be isolated with this approach and, relative to the other fractions, was low in lignin, high in ash, highly hygroscopic, and showed an improved response to mild alkaline pretreatment and enzymatic hydrolysis at low enzyme loadings. Overall, these results demonstrate how heterogeneity within sorghum stems can be exploited using physical fractionation approaches to yield fractions enriched in desired properties that may allow for more streamlined processing.
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| 6. |
- Li, Muyang, et al.
(författare)
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Prediction of Cell Wall Properties and Response to Deconstruction Using Alkaline Pretreatment in Diverse Maize Genotypes Using Py-MBMS and NIR
- 2017
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Ingår i: Bioenergy Research. - : Springer. - 1939-1234 .- 1939-1242. ; 10:2, s. 329-343
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we explore the ability of several characterization approaches for phenotyping to extract information about plant cell wall properties in diverse maize genotypes with the goal of identifying approaches that could be used to predict the plant’s response to deconstruction in a biomass-to-biofuel process. Specifically, a maize diversity panel was subjected to two high-throughput biomass characterization approaches, pyrolysis molecular beam mass spectrometry (py-MBMS) and near-infrared (NIR) spectroscopy, and chemometric models to predict a number of plant cell wall properties as well as enzymatic hydrolysis yields of glucose following either no pretreatment or with mild alkaline pretreatment. These were compared to multiple linear regression (MLR) models developed from quantified properties. We were able to demonstrate that direct correlations to specific mass spectrometry ions from pyrolysis as well as characteristic regions of the second derivative of the NIR spectrum regions were comparable in their predictive capability to partial least squares (PLS) models for p-coumarate content, while the direct correlation to the spectral data was superior to the PLS for Klason lignin content and guaiacyl monomer release by thioacidolysis as assessed by cross-validation. The PLS models for prediction of hydrolysis yields using either py-MBMS or NIR spectra were superior to MLR models based on quantified properties for unpretreated biomass. However, the PLS models using the two high-throughput characterization approaches could not predict hydrolysis following alkaline pretreatment while MLR models based on quantified properties could. This is likely a consequence of quantified properties including some assessments of pretreated biomass, while the py-MBMS and NIR only utilized untreated biomass.
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| 7. |
- Liu, Tongjun, et al.
(författare)
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Coupling alkaline pre-extraction with alkaline-oxidative post-treatment of corn stover to enhance enzymatic hydrolysis and fermentability
- 2014
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Background: A two-stage chemical pretreatment of corn stover is investigated comprising an NaOH pre-extraction followed by an alkaline hydrogen peroxide (AHP) post-treatment. We propose that conventional one-stage AHP pretreatment can be improved using alkaline pre-extraction, which requires significantly less H2O2 and NaOH. To better understand the potential of this approach, this study investigates several components of this process including alkaline pre-extraction, alkaline and alkaline-oxidative post-treatment, fermentation, and the composition of alkali extracts.Results: Mild NaOH pre-extraction of corn stover uses less than 0.1 g NaOH per g corn stover at 80 degrees C. The resulting substrates were highly digestible by cellulolytic enzymes at relatively low enzyme loadings and had a strong susceptibility to drying-induced hydrolysis yield losses. Alkaline pre-extraction was highly selective for lignin removal over xylan removal; xylan removal was relatively minimal (similar to 20%). During alkaline pre-extraction, up to 0.10 g of alkali was consumed per g of corn stover. AHP post-treatment at low oxidant loading (25 mg H2O2 per g pre-extracted biomass) increased glucose hydrolysis yields by 5%, which approached near-theoretical yields. ELISA screening of alkali pre-extraction liquors and the AHP post-treatment liquors demonstrated that xyloglucan and beta-glucans likely remained tightly bound in the biomass whereas the majority of the soluble polymeric xylans were glucurono (arabino) xylans and potentially homoxylans. Pectic polysaccharides were depleted in the AHP post-treatment liquor relative to the alkaline pre-extraction liquor. Because the already-low inhibitor content was further decreased in the alkaline pre-extraction, the hydrolysates generated by this two-stage pretreatment were highly fermentable by Saccharomyces cerevisiae strains that were metabolically engineered and evolved for xylose fermentation.Conclusions: This work demonstrates that this two-stage pretreatment process is well suited for converting lignocellulose to fermentable sugars and biofuels, such as ethanol. This approach achieved high enzymatic sugars yields from pretreated corn stover using substantially lower oxidant loadings than have been reported previously in the literature. This pretreatment approach allows for many possible process configurations involving novel alkali recovery approaches and novel uses of alkaline pre-extraction liquors. Further work is required to identify the most economical configuration, including process designs using techno-economic analysis and investigating processing strategies that economize water use.
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| 8. |
- Scott, Felipe, et al.
(författare)
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Corn stover semi-mechanistic enzymatic hydrolysis model with tight parameter confidence intervals for model-based process design and optimization
- 2015
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 177, s. 255-265
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Tidskriftsartikel (refereegranskat)abstract
- Uncertainty associated to the estimated values of the parameters in a model is a key piece of information for decision makers and model users. However, this information is typically not reported or the confidence intervals are too large to be useful. A semi-mechanistic model for the enzymatic saccharification of dilute acid pretreated corn stover is proposed in this work, the model is a modification of an existing one providing a statistically significant improved fit towards a set of experimental data that includes varying initial solid loadings (10 to 25 % w/w) and the use of the pretreatment liquor and washed solids with or without supplementation of key inhibitors. A subset of 8 out of 17 parameters was identified, showing sufficiently tight confidence intervals to be used in uncertainty propagation and model analysis, without requiring interval truncation via expert judgment.
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