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Li, Mi

Publications and source records attributed to Li, Mi.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

The effect of lignin degradation products on the generation of pseudo-lignin during dilute acid pretreatment

Pseudo-lignin is an insoluble material that tends to deposit on acidic pretreated fiber surface and negatively impacts the biological conversion of biomass to valued added products. Employing a laboratory generated acidic hydrolysate solution from dilute acid pretreatment of bamboo residues, we sought to seek an improved understanding of pseudo-lignin formation from fragmented carbohydrates. In addition, we also performed experiments to investigate how lignin model compounds interact with carbohydrates en route to pseudo-lignin’s formation. The yields of pseudo-lignin generated from xylose (CXPL) were higher than those generated from glucose (CGPL). Gas chromatography-Mass spectrometry and Foloin-Ciocalteau analysis suggested that there were more aromatic compounds in hydrolyzate during CGPL’s formation. The presence of lignin phenolic model compounds had both a positive and negative effect upon quantitative yields of pseudo-lignin. Gel permeation chromatography and NMR analysis ( 31 P and 2D-HSQC NMR) of the pseudo-lignin samples generated in the presence and absence of 4-hydroxybenzoic acid (4-HA), employed as a lignin model compound, revealed drastic differences in molecular weight, changes in hydroxyl group content, and hydrocarbon bonds, suggesting significant differences in the pseudo-lignin reaction pathways when certain lignin model compounds are present. Finally, our findings demonstrate the effects of both hemicellulose carbohydrate makeup and lignin model compound impact on the formation of pseudo-lignin and its chemical properties, suggesting a potential way to minimize pseudo-lignin formation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Synthesis, Characterization, and Utilization of a Lignin-Based Adsorbent for Effective Removal of Azo Dye from Aqueous Solution

How to effectively remove toxic dyes from the industrial wastewater using a green low-cost lignocellulose-based adsorbent, such as lignin, has become a topic of great interest but remains quite challenging. In this study, cosolvent-enhanced lignocellulosic fractionation (CELF) pretreatment and Mannich reaction were combined to generate an aminated CELF lignin which is subsequently applied for removal of methylene blue and direct blue (DB) 1 dye from aqueous solution. 31P NMR was used to track the degree of amination, and an orthogonal design was applied to determine the relationship between the extent of amination and reaction parameters. The physicochemical, morphological, and thermal properties of the aminated CELF lignin were characterized to confirm the successful grafting of diethylenetriamine onto the lignin. The aminated CELF lignin proved to be an effective azo dye-adsorbent, demonstrating considerably enhanced dye decolorization, especially toward DB 1 dye (>90%). It had a maximum adsorption capacity of DB 1 dye of 502.7 mg/g, and the kinetic study suggested the adsorption process conformed to a pseudo-second-order kinetic model. The isotherm results also showed that the modified lignin-based adsorbent exhibited monolayer adsorption. The adsorbent properties were mainly attributed to the incorporated amine functionalities as well as the increased specific surface area of the aminated CELF lignin.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Black Liquor Valorization by Using Marine Protist Thraustochytrium striatum and the Preliminary Metabolic Mechanism Study

Black liquor that contains various phenolic compounds from lignin solubilization has been the main byproduct of alkaline pretreatment of lignocellulosic biomass in the biorefinery. In this study, black liquor from alkaline pretreatment of corn stover was used as a sole carbon source for the cultivation of a marine protist, Thraustochytrium striatum. It was found that this strain can grow on black liquor and accumulate valuable products (e.g., fatty acids and carotenoids) simultaneously. Under optimal conditions (pH = 7 and NH 4 Cl = 2 g/L), the cell mass concentration reached 5.2 g/L with total aromatics decreased from 8.18 to 3.09 g/L within 7 day incubation. Fed-batch cultivation was adopted to increase the contents of total fatty acids and carotenoids to 13% and 0.24 mg/g dry cell mass, respectively. Although various compounds such as sugars and organic acids were detected in black liquor and consumed during microbial fermentation as carbon sources, lignin-derived compounds were identified as the major substrates for T. striatum fermentation. Of total aromatics consumed, monomers including p-coumaric acid, ferulic acid, vanillin, and syringaldehyde were observed to be consumed and converted while polymeric fragments were also depolymerized and degraded. Under optimal conditions, around 50% of the total aromatics was consumed. The dynamic changes of compounds in black liquor indicated that diverse metabolic processes were involved in black liquor degradation and utilization by T. striatum. A strong adaptation of T. striatum to a wide range of pH (3–9) was also observed during black liquor fermentation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Stereolithography 3D Printing of Lignin-Reinforced Composites with Enhanced Mechanical Properties

Due to the availability, biodegradability, and biological effects, lignin has emerged as an interesting alternative to petroleum-based compounds for developing sustainable chemicals, materials, and composites. In this study, lignin at various concentrations was incorporated into methacrylate resin via solution blending to fabricate lignin-reinforced composites using stereolithography apparatus three-dimensional printing. Softwood kraft lignin in the amounts of 0.2, 0.4, 0.5, 0.8, and 1.0 wt % in the methacrylate resin was used as a printing ink, and the gel contents and relative contents of the residual resin in the printed samples with various lignin concentrations were measured. The effects of the lignin on the ultimate mechanical properties of the non-postcured and postcured printed composites were determined. The tensile testing results revealed that the incorporation of lignin in the composite increased the tensile strength by 46–64% and Young’s modulus by 13–37% for the postcured printed composites compared with that of the control sample (no lignin added). Employing a 0.4 wt % softwood kraft lignin, the tensile strength of the postcured printed composite reached the highest value of 49.0 MPa, which was a 60% increase in comparison to that of the control sample with 30.7 MPa. Scanning electron microscopy images of the fracture samples illustrated that the lignin-incorporated composites exhibited a rougher fracture surface that can presumably dissipate the stress, which could be a contributing factor for the mechanical enhancement.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Recycling benzene and ethylbenzene from in-situ catalytic fast pyrolysis of plastic wastes

Recovering waste plastics by catalytic fast pyrolysis to selectively generate aromatic hydrocarbons is a promising approach to dispose of solid wastes. In the present work, catalytic conversion of polystyrene over ultra-stable Y zeolites (USY) was conducted to directionally produce benzene and ethylbenzene. Experimental results indicated that catalyst type considerably affected the distribution of aromatic hydrocarbons, and USY with high surface area (734 m 2 /g), large pore size (5.6 nm), and an abundant amount of strong acid sites (1.21 mmol/g) exhibited the most effective shape selectivity for ethylbenzene and benzene generation as the yield enhanced rate reached 401.8% and 61.1%, respectively. We note plastic type also played a vital role in the formation of desirable aromatic hydrocarbons, and polystyrene was more beneficial to the production of ethylbenzene as a 54-fold increase was obtained compared to polycarbonate in the catalytic degradation process. Concerning reaction conditions to maximize the formation of benzene and ethylbenzene in the catalytic decomposition of polystyrene, the catalyst/feedstock mass ratio, Si/Al mole ratio in USY, and catalytic conversion temperature could be optimized at 1.5, 5.3, and 650 °C, respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Catalytic fast co-pyrolysis of bamboo sawdust and waste plastics for enhanced aromatic hydrocarbons production using synthesized CeO 2 /γ-Al 2 O 3 and HZSM-5

Fast co-pyrolysis of bamboo sawdust and waste plastic (linear low-density polyethylene, LLDPE) over a dual catalytic stage of synthesized CeO 2 /γ-Al 2 O 3 and HZSM-5 was conducted to enhance aromatic hydrocarbons production. Experimental results indicated that the catalyst to biomass (C/B) mass ratio played a determining role in the formation of hydrocarbon intermediates and a C/B mass ratio of 4 facilitated the production of aromatic hydrocarbons. Dual catalytic fast co-pyrolysis of bamboo sawdust and LLDPE using synthesized CeO 2 /γ-Al 2 O 3 and HZSM-5 increased the concentration of aromatic hydrocarbons and a CeO 2 /γ-Al 2 O 3 to HZSM-5 mass ratio of 1:3 maximized the target products. The content of aromatic hydrocarbons was increased at first and then decreased as the LLDPE percentage was elevated from 20% to 100% during the dual catalytic fast co-pyrolysis process, with the highest concentration obtained at 75% LLDPE percentage. In addition, the additive effect of monocyclic aromatic hydrocarbons was enhanced with the increasing of LLDPE percentage in the feedstock blends, and higher LLDPE proportion favored the production of xylenes, ethylbenzene, and alkylbenzenes as the additive effects were significantly promoted.

09 BIOMASS FUELS↗
DOE OSTI2019

Cross-Linked Nanocellulosic Materials and Their Applications

Nanocelluloses (NCs) have remarkable mechanical properties and contain abundant surface functional groups that can be modified or cross-linked with other materials. They have been widely used as an environment-friendly reinforcing agent in polymer composites. However, for applications that are carried out in humid environments or aqueous suspensions, hydrophilicity of NCs lower their mechanical integrity. Hence, cross-linking techniques have been investigated in recent years for preparing NC-based materials that are dimensionally stable under humid or aqueous environments and have better physicochemical properties. This Minireview examines the quickly growing field of cross-linked NC-based materials, which have many benefits including improved aqueous, structural, mechanical, and thermal stability. In addition, the potential application of cross-linked NC-based materials in adsorption of heavy metal is discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Catalytic conversion of rubber wastes to produce aromatic hydrocarbons over USY zeolites: Effect of SiO 2 /Al 2 O 3 mole ratio

Catalytic conversion of rubber wastes to produce an alternative fuel resource is a promising approach to dispose of solid wastes and address environmental issues. In this study, catalytic fast pyrolysis (CFP) of rubber wastes over acidic zeolites was conducted, and the effect of SiO 2 /Al 2 O 3 mole ratio of USY zeolites on the formation of aromatic hydrocarbons was explored. Experimental results indicated that alkenes and aromatic hydrocarbons were the main pyrolytic products obtained from fast pyrolysis of rubber wastes, and the pyrolysis temperature played a vital role in the formation of aromatics with the highest concentration achieved at 750 °C. Furthermore, catalyst types also affected the catalytic degradation of rubber wastes since limonene was completely decomposed in the presence of zeolites. Compared to SAPO-34, zeolites with higher external surface area, stronger Brønsted acid sites, and larger pore size, including USY, HY, and Hβ, were more effective in the production of aromatic hydrocarbons with the highest content obtained from USY catalyzed run. Given the observed effect of SiO 2 /Al 2 O 3 mole ratio of USY zeolites on the formation of aromatic hydrocarbons during the CFP of rubber wastes, USY with low SiO 2 /Al 2 O 3 ratio of 5.3 was more beneficial to the generation of aromatic hydrocarbons, while that with higher SiO 2 /Al 2 O 3 mole ratio (11.5) facilitated the formation of alkenes. Simultaneously, the product distribution of aromatic hydrocarbons obtained from CFP of rubber wastes over USY zeolites was dominated by xylenes, alkylbenzenes, and toluene, and USY with SiO 2 /Al 2 O 3 mole ratio of 5.3 was more active in the production of toluene and xylenes.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

New insights into structural and functional relationships between LonA proteases and ClpB chaperones

LonA proteases and ClpB chaperones are key components of the protein quality control system in bacterial cells. LonA proteases form a unique family of ATPases associated with diverse cellular activities (AAA + ) proteins due to the presence of an unusual N-terminal region comprised of two domains: a β-structured N domain and an α-helical domain, including the coiled-coil fragment, which is referred to as HI(CC). The arrangement of helices in the HI(CC) domain is reminiscent of the structure of the H1 domain of the first AAA + module of ClpB chaperones. It has been hypothesized that LonA proteases with a single AAA + module may also contain a part of another AAA + module, the full version of which is present in ClpB. Here, we established and tested the structural basis of this hypothesis using the known crystal structures of various fragments of LonA proteases and ClpB chaperones, as well as the newly determined structure of the Escherichia coli LonA fragment (235–584). The similarities and differences in the corresponding domains of LonA proteases and ClpB chaperones were examined in structural terms. The results of our analysis, complemented by the finding of a singular match in the location of the most conserved axial pore-1 loop between the LonA NB domain and the NB2 domain of ClpB, support our hypothesis that there is a structural and functional relationship between two coiled–coil fragments and implies a similar mechanism of engagement of the pore-1 loops in the AAA + modules of LonAs and ClpBs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Downregulation of pectin biosynthesis gene GAUT4 leads to reduced ferulate and lignin-carbohydrate cross-linking in switchgrass

Abstract Knockdown (KD) expression of GAlactUronosylTransferase 4 ( GAUT4 ) in switchgrass improves sugar yield and ethanol production from the biomass. The reduced recalcitrance of GAUT4 -KD transgenic biomass is associated with reduced cell wall pectic homogalacturonan and rhamnogalacturonan II content and cross-linking, and the associated increases in accessibility of cellulose to enzymatic deconstruction. To further probe the molecular basis for the reduced recalcitrance of GAUT4 -KD biomass, potential recalcitrance-related factors including the physicochemical properties of lignin and hemicellulose are investigated. We show that the transgenic switchgrass have a lower abundance of ferulate and lignin-carbohydrate complex cross-linkages, reduced amounts of residual arabinan and xylan in lignin-enriched fractions after enzymatic hydrolysis, and greater coalescence and migration of lignin after hydrothermal pretreatment in comparison to the wild-type switchgrass control. The results reveal the roles of both decreased lignin-polymer and pectin cross-links in the reduction of recalcitrance in PvGAUT4 -KD switchgrass.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Crystal structures of the complex of a kallikrein inhibitor from Bauhinia bauhinioides with trypsin and modeling of kallikrein complexes

Structures of a recombinant Kunitz-type serine protease inhibitor from Bauhinia bauhinioides (BbKI) complexed with bovine trypsin were determined in two crystal forms. The crystal structure with the L55R mutant of BbKI was determined in space group P 6 4 at 1.94 Å resolution and that with native BbKI in the monoclinic space group P 2 1 at 3.95 Å resolution. The asymmetric unit of the latter crystals contained 44 independent complexes, thus representing one of the largest numbers of independent objects deposited in the Protein Data Bank. Additionally, the structure of the complex with native BbKI was determined at 2.0 Å resolution from P 6 4 crystals isomorphous to those of the mutant. Since BbKI has previously been found to be a potent inhibitor of the trypsin-like plasma kallikrein, it was also tested against several tissue kallikreins. It was found that BbKI is a potent inhibitor of human tissue kallikrein 4 (KLK4) and the chymotrypsin-like human tissue kallikrein 7 (KLK7). Structures of BbKI complexed with the catalytic domain of human plasma kallikrein were modeled, as well as those with KLK4 and KLK7, and the structures were analyzed in order to identify the interactions that are responsible for inhibitory potency.

Li, Mi↗
DOE OSTI2018

Catalytic fast co-pyrolysis of bamboo sawdust and waste tire using a tandem reactor with cascade bubbling fluidized bed and fixed bed system

Catalytic fast co-pyrolysis (co-CFP) of bamboo sawdust and waste tire over HZSM-5 and MgO was conducted using a tandem pyrolysis and upgrading system which consists of a bubbling fluidized bed and a fixed bed reactor. HZSM-5 mixed and sequential with MgO modes were studied to explore the additive effect for the promotion of aromatic hydrocarbons. Experimental results indicated that co-CFP of bamboo sawdust with waste tire over pure HZSM-5 increased the yields of pyrolysis oil and char, while the gas yield decreased with the increasing of waste tire percentage in the feedstock blends. The product distribution of pyrolysis oil obtained from co-CFP of bamboo sawdust and waste tire over pure HZSM-5 was dominated by aromatic hydrocarbons, and the relative concentration increased from 26.71 to 71.50% as the waste tire percentage elevated from 0 to 60 wt%. Co-CFP of bamboo sawdust and waste tire using HZSM-5 mixed with MgO mode produced a higher yield of pyrolysis oil than the sequential mode when HZSM-5/MgO mass ratio was raised from 1:4 to 1:1. However, the sequential mode was proved to be more effective in the promotion of aromatic hydrocarbons than the mixed mode at a higher HZSM-5 proportion. A positive additive effect for alkylbenzenes was found when the sequential mode was used at varying HZSM-5/MgO mass ratios. Regarding the olefins, C10 olefins were main products, and limonene selectivity increased at first and then decreased with the highest selectivity of 38.87% occurring at HZSM-5/MgO of 2:3 in the mixed mode case. In conclusion, the additive effect of HZSM-5 and MgO indicated that both the mixed and sequential modes inhibited the formation of polycyclic aromatic hydrocarbons with the most significant additive effect obtained at HZSM-5/MgO mass ratio of 1:1 using the mixed mode.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Catalytic Conversion of Bamboo Sawdust over ZrO 2 –CeO 2 /γ-Al 2 O 3 to Produce Ketonic Hydrocarbon Precursors and Furans

Here, a series of metal oxides including ZrO 2 /γ-Al 2 O 3 , CeO 2 /γ-Al 2 O 3 , and ZrO 2 –CeO 2 /γ-Al 2 O 3 were synthesized and employed to conduct catalytic fast pyrolysis of bamboo sawdust via an analytical pyrolyzer/gas chromatograph/mass spectrometer (Py-GC/MS) to produce hydrocarbon precursors such as ketones and furans. Experimental results illustrated that the use of metal oxides enhanced the formation of ketones and monoaromatic hydrocarbons compared to catalyst-free trial. Among the metal oxides, ZrO 2 –CeO 2 /γ-Al 2 O 3 exhibited the most significant ketonization and aldol condensation activities yielding the highest concentration of linear and cyclic ketones. In addition, nonacidic oxygenates such as furfural, acetol, butanedial, 2,3-dihydrobenzofuran, and methyl acetate, were efficiently converted into hydrocarbon precursors over metal oxides. A dual catalytic bed system integrating ZrO 2 –CeO 2 /γ-Al 2 O 3 and HZSM-5 significantly facilitated the production of aromatic hydrocarbons compared to pure HZSM-5 catalytic run. The use of ZrO 2 –CeO 2 /γ-Al 2 O 3 mixed with HZSM-5 mode maximized the formation of xylenes, while ZrO 2 –CeO 2 /γ-Al 2 O 3 mixed with bamboo sawdust catalytic trial increased the concentration of benzene, toluene, and alkylbenzenes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗