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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Facilitating enzymatic hydrolysis with a novel guaiacol-based deep eutectic solvent pretreatment

In this work, we established a novel deep eutectic solvent (DES) using lignin-derived guaiacol as hydrogen bond donor (HBD). The sole ChCl/guaiacol system was found to be inefficient for the fractionation of wheat straw (WS), while the incorporation of trace AlCl 3 significantly facilitated the degradation of hemicellulose and lignin, resulting in a complete enzymatic digestibility of the pretreated WS. Further, this study revealed that the DES-degraded lignin was readily precipitated during the washing process, and thus hindered the enzymatic hydrolysis of poplar and bamboo (with hydrolysis yield of 42.03% and 71.67%, respectively). Alkali washing offers a possible approach to remove the precipitated lignin, after which a near 100% hydrolysis yield was also obtained for poplar and bamboo.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Revealing the mechanism of surfactant-promoted enzymatic hydrolysis of dilute acid pretreated bamboo

Here, to improve the enzymatic digestibility of dilute acid pretreated bamboo residue (DABR), surfactants including PEG 4000 and Tween 80 were added to prevent the non-productive adsorption between residual lignin and enzyme. At the optimal loadings (e.g., 0.2 and 0.3 g surfactant/g lignin), the enzymatic digestibility of DABR improved from 29.4% to 64.6% and 61.6% for PEG 4000 and Tween 80, respectively. Furthermore, the promoting mechanism of these surfactants on enzymatic hydrolysis was investigated by real-time surface plasmon resonance (SPR) and fluorescence spectroscopy. Results from SPR analysis showed that Tween 80 outperformed PEG 4000 in terms of dissociating the irreversible cellulase adsorption onto lignin. Fluorescence quenching mechanism revealed that PEG 4000 and Tween 80 intervened the interaction between lignin and cellulase by hydrogen bonds/Van der Waals and hydrophobic action, respectively. This work provided an in-depth understanding of the mechanisms of PEG 4000 and Tween 80 on enhancing the enzymatic hydrolysis efficiency.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Uses of H 2 and CO 2 gases in hydrometallurgical processes: Potential towards sustainable pretreatment, metal production and carbon neutrality

Hydrometallurgical practices represent a vital area of focus within the metallurgical sector, and it is critical that these practices are carried out in an environmentally friendly manner in order to promote sustainability and responsibility. One promising approach is the use of hydrogen gas (H 2 ), known for its ‘green’ properties, along with the pollutant carbon dioxide CO 2 ), at various stages within the hydrometallurgical field. This review provides a detailed overview of the utilization of H 2 and CO 2 gases in the hydrometallurgical field, encompassing key stages including pretreatment, leaching, and metal recovery. Theoretical underpinnings are also provided for each stage, along with an overview of cutting-edge approaches such as application of supercritical CO 2 . Challenges and future directions associated with H 2 and CO 2 utilization are also discussed. This review serves an important step towards advancing sustainable and responsible hydrometallurgical processes in the pursuit of carbon neutrality.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Membrane Bioreactor Pretreatment of High-Salinity O&G Produced Water

Produced water (PW) from oil and gas production contains variable constituents that are difficult to remove with conventional treatment processes. The focus of this study was to explore the long-term performance of a membrane bioreactor (MBR) for the removal of organic constituents from PW and how performance and microbial community composition are affected by progressively increasing salinity and introduction of PW from different shale basins around the United States. Dissolved organic carbon removal from the PW remained consistent throughout the study, averaging 86% from the Denver-Julesburg basin PW and 66% removal from the Permian basin PW. Surfactant removal was less consistent, showing 87% removal of poly(ethylene glycols) (PEGs) at a total dissolved solid (TDS) concentration of 40 g/L but only 58% removal at a TDS concentration of 100 g/L. Diversity in the microbial community decreased during reactor establishment but increased at TDS concentrations above 80 g/L. Finally, the results of this study suggest that MBRs can be effective PW pretreatment processes even at high salinities.

42 ENGINEERING↗
DOE OSTI2021

Conversion of High-Solids Hydrothermally Pretreated Bioenergy Sorghum to Lipids and Ethanol Using Yeast Cultures

Glucose and xylose are the major sugars in cellulosic hydrolysates. The cellulosic sugars can be used for the production of biofuels and value-added bioproducts. In this study, lipid and ethanol were produced from bioenergy sorghum syrups using engineered yeasts. Here, bioenergy sorghum was hydrothermally pretreated at 50% solids loading in a continuous reactor system and mechanically refined sequentially using a burr mill to improve biomass accessibility for hydrolysis. Fed-batch enzymatic hydrolysis was conducted with 50% w/v solids loading to achieve 230 g/L sugar concentration. Different strains of Rhodosporidium toruloides were used to ferment sugars into lipids, and the highest lipid yield of 9.2 g/L was observed. The lipid yield was improved to 19.0 g/l by implementing a two-stage culture where once the sugars were exhausted in the first stage, the yeast was introduced into fresh hydrolysate without adding nitrogen. For ethanol production, the engineered Saccharomyces cerevisiae SR8ΔADH6 was utilized to coferment glucose and xylose. Additionally, the effects of nutrient media (YP, YNB/urea, and urea), cellulosic sugar concentration, and sulfite addition were investigated to optimize the ethanol yield from sorghum syrups. The optimal ethanol yield at 73.3% was obtained from the YNB/urea culture consisting of 34 g glucose/L and 17 g xylose/L.

09 BIOMASS FUELS↗
DOE OSTI2025

Rheological Properties of Enzymatically Hydrolyzed Corn Stover Pretreated via Deacetylation and Mechanical Refining

Lignocellulosic biomass is a feedstock for fuels and chemicals that does not compete with food resources and has less contaminants than refuse-derived biomass feedstocks. To convert lignocellulosics to biofuels or value-added products, multiple processing steps are typically necessary. One method of producing biofuels from lignocellulosic biomass utilizes a deacetylation and mechanical refining pretreatment and an enzymatic hydrolysis reaction to produce fermentable sugars from cellulose and hemicellulose. The rheological properties of biomass, such as yield stress and plastic viscosity, change during enzymatic hydrolysis and alter the energy requirements for pumping and mixing, an important consideration for the design of processing equipment. The dynamic changes in rheological properties that occur in a corn stover feedstock undergoing enzymatic hydrolysis are characterized in this work, and the influence on pressure losses in piping systems is estimated. Two rheometer geometries were fabricated with stereolithography 3D printing to reduce wall slip and sample ejection. The slurries have complex rheological behaviors that include shear-thinning behavior. Shear stress ramps were performed on samples at 20 and 50 degrees C using the custom geometries, and the Herschel-Bulkley model was fit to the data. The dynamic nature of the rheological properties is correlated with changes in the average fiber length at various extents of reaction, and the influence of solids concentration on the observed rheology and piping pressure losses is discussed.

09 BIOMASS FUELS↗
DOE OSTI2022

Transcriptomic Data Sets for Zymomonas mobilis 2032 during Fermentation of Ammonia Fiber Expansion (AFEX)-Pretreated Corn Stover and Switchgrass Hydrolysates

The transcriptomes of Zymomonas mobilis 2032 were captured during the fermentation of ammonia fiber expansion (AFEX)-pretreated corn stover and switchgrass hydrolysates containing different concentrations of glucose and xylose. RNA samples were collected when Z. mobilis was fermenting glucose or xylose. Here, we present transcriptome sequencing (RNA-Seq) data obtained during separate phases of glucose or xylose consumption.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Data for Conversion of High-Solids Hydrothermally Pretreated Bioenergy Sorghum to Lipids and Ethanol Using Yeast Cultures

Glucose and xylose are the major sugars present in cellulosic hydrolysates. The cellulosic sugars can be used for the production of platform chemicals. In this study, productions of lipid and ethanol by yeasts were compared for concentrated bioenergy sorghum syrup. Bioenergy sorghum was hydrothermally pretreated at 50% w/w solids in a continuous industrial reactor and sequentially mechanically refined using a burr mill to improve biomass accessibility for hydrolysis. Fed-batch enzymatic hydrolysis was conducted with 50% w/v solids loading and cellulase cocktail (50 FPU/g biomass) to achieve 230 g/L sugar concentration. Various strains of Rhodosporidium toruloides were evaluated for converting sugars into lipids, and strain Y-6987 had the highest lipid titer (9.2 g/L). The lipid titer was improved to 19.0 g/L by implementing a two-stage culture scheme, where the first stage was optimized for yeast growth and the second for lipid production. For ethanol production, the engineered Saccharomyces cerevisiae SR8ΔADH6 was used to coferment glucose and xylose. Ethanol fermentation was optimized for media nutrients (YP, YNB/urea, and urea), cellulosic sugar concentration, and sulfite conditioning to maximize the ethanol concentration from sorghum syrups. Fermentation of 70% v/v concentrated hydrolysate conditioned with sulfite produces 50.1 g/L ethanol from 141 g/L of sugars.

Conversion↗
DOE OSTI2020

Physico-chemical properties of lignin fractions from acid pretreated corn stover and their effects on enzymatic hydrolysis of microcrystalline cellulose

Lignin has been shown to be a recalcitrance factor in many biomass conversion studies. To better understand the effects of lignin on cellulose conversion, different lignin fractions were extracted from the same dilute acid pretreated corn stover by three sequential isolation methods, namely ethanol extraction, dioxane extraction, and enzyme purification. The physicochemical properties of each lignin fraction including molecular weight distribution, surface area, surface charge, and other structural features varied, depending on the isolation methods. All three lignin fractions had negative surface charges, and ethanol-extracted lignin carried the highest surface charges, followed by dioxane-extracted lignin and cellulase-purified residual lignin. These physicochemical properties of lignin fractions also resulted in different extent of inhibitory effects on enzymatic hydrolysis of microcrystalline cellulose (MCC). Dioxane-extracted lignin exhibited the highest inhibitory effect on glucose release from MCC, followed by the cellulase-purified residual lignin fraction and ethanol-extracted lignin. Furthermore, lignin fractions with higher contents of syringyl (S) substructure and β-O-4 aryl ether interunit linkages showed a stronger negative effect on cellulase hydrolysis of MCC.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Evaluation of Pozzolan-substituted Cast Stone for Pretreated Hanford Tank Waste

Portland cement. The future availability of quality Class F fly ash has come into question as coal-fired power plants are being converted to gas or taken offline. Consequently, alternative pozzolanic reagents are being evaluated for fly ash replacement in cementitious matrices for treating radioactive waste and debris. In 2023 and 2024, Savannah River National Laboratory (SRNL) was funded to evaluate natural pozzolans for the replacement of Class F fly in the Savannah River Site (SRS) Saltstone formulation. Based on the promising results and uncertain availability of Class F fly ash in the northwestern US, Hanford Tank Waste Operations & Closure, LLC (H2C) requested SRNL to evaluate the potential for substituting natural pozzolans in the Hanford West Area Pretreated Low Activity Tank Waste (PTW/LAW) Cast Stone formulation1 . Task 1 in this request was to determine the change in Cast Stone volume resulting from stabilization/solidification of 1 L of PTW/LAW tank waste. The densities of three (Hess Pumice, tephra pumice, and clinoptilolite zeolite) pozzolan-substituted Baseline Cast Stone mixes were determined, and volume changes relative to the fly ash-Baseline Mix with a water-to-dry mix = 0.40 were calculated.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

LDR Inorganic Spiked Simulants in Pozzolan-Substituted Cast Stone for Hanford Pretreated Low-Activity Tank Waste

Pretreated Low Activity Waste (PTW/LAW) at the Hanford Site, is currently projected for disposition through a cementitious waste form. The current standard formulation, Cast Stone, uses Class F fly ash, blast furnace slag, and Portland cement. However, the future availability of Class F fly ash is uncertain, as many coal-fired power plants—the source of this byproduct—are being decommissioned or converted to natural gas. This issue has prompted research into identifying and evaluating suitable alternative materials to replace fly ash in the cementitious waste forms used by the Department of Energy (DOE). The Savannah River National Laboratory (SRNL) successfully identified four natural pozzolans for the replacement of Class F fly ash in the current Savannah River Site (SRS) low-level waste (LLW) form, Saltstone.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗