Low-temperature Production Research Articles

Investigation of low-temperature lipase production and enzymatic properties of Aspergillus Niger

To obtain the optimum fermentation medium and circumstances for extracellular lipase construction (as an important biocatalyst and promising industrial enzyme) by Aspergillus Niger, the fermentation conditions of Aspergillus Niger were optimized by single factor and response surface design, the enzymatic properties of the crude enzyme were studied. The results displayed that the optimum fermentation medium was soluble starch 4%, (NH4)2SO4 0.1%, K2HPO4 0.1%, MgSO4·7H2O 0.05%, peptone 3%, olive oil 1.05% and initial pH 7. The optimal fermentation conditions were 30℃, the sample size was 26 mL/250 mL and the shaking speed was 213 r/min. The optimized lipase activity was 1.55 U/mL, which was 7.75 times of the pre-optimized lipase. It was found that when the pH value of lipase was 7.0, the activity of lipase reached its maximum value of 79.3±6.82%. When pH value was between 6.0 and 8.0, the activity of lipase could be kept above 60% and the stability was good. At the same time, through temperature stability of lipase, found that the lipase was stable at 25℃- 35℃, its activity could reach more than 70%. When activity of enzyme reaches to maximum 107.6±9.57%, the temperature was 30℃.

Molecular Characterization of a Mesophilic Cellobiose 2-Epimerase That Maintains a High Catalytic Efficiency at Low Temperatures.

Cellobiose 2-epimerase (CE) can catalyze bioconversion of lactose to its prebiotic derivative epilactose. The catalytic property of a novel CE from Treponema brennaborense (Trbr-CE) was investigated. Trbr-CE showed the highest catalytic efficiency of epimerization toward lactose among all of the previously reported CEs. This enzyme's specific activity could reach as high as 208.5 ± 5.3 U/mg at its optimum temperature, which is 45 °C. More importantly, this enzyme demonstrated a considerably high activity at low temperatures, suggesting Trbr-CE as a promising enzyme for industrial low-temperature production of epilactose. This structurally flexible enzyme exhibited a comparatively high binding affinity toward substrates, which was confirmed by both experimental verification and computational analysis. Molecular dynamics (MD) simulations and binding free energy calculations were applied to provide insights into molecular recognition upon temperature changes. Compared with thermophilic CEs, Trbr-CE presents a more negative enthalpy change and a higher entropy change when the temperature drops.

Effect of Microstructure on Low-Temperature Impact Toughness of Multi-Pass Weld Metal of 1 GPa Class High Strength Steel

A 1 GPa class weld metal was prepared by multi-pass welding using a prototype flux-cored wire, and the correlation between microstructure and low-temperature impact toughness of the weld metal was investigated. The microstructure of the as-deposited columnar region and the equiaxed region reheated by subsequent welding passes was observed, and it was found that low-temperature transformation products such as bainite and martensite mainly developed in both regions. Since the prior austenite grains were coarse in the columnar region, the effective grain size of the final microstructure could be large; in this case, it was confirmed that the low-temperature impact toughness of the weld metal was very low. However, in the weld metal used in this study, acicular ferrite was formed inside the grains of the columnar region; the effective grain size and grain boundary misorientation distribution of the final microstructure were similar to those of the equiaxed region, and a good low-temperature impact toughness of the weld metal was obtained. Key words: High strength steel, Multi-pass weld metal, Acicular ferrite, Impact toughness

A stable Cu-polyatomic-cluster catalyst: Critical for methanol reforming deNOx at mild temperature

The practical application of traditional H2-SCR is hindered by its rare hydrogen supply (0.5-2%) and the safety risk of hydrogen transportation and storage. Therefore, this paper proposes a new process to reduce the hydrogen utilization threshold by coupling low-temperature inline hydrogen production and hydrogen deNOx. We synthesized a bifunctional catalyst: Cux/C-MnPdOy@Ni, which could achieve inline hydrogen production above uniformed-dispersion Cu-polyatomic-cluster Cux/C center and coupled with hydrogen deNOx over MnPdOy center. Online-GC monitored the generation of H2 during the process, which confirmed the coupling reaction's feasibility. The candidate Cu800/C-MnPdOy@Ni can maintain over 90% deNOx efficiency at 120 °C under GHSV = 22000 h−1 + water-alcohol ratio (ω) = 1.3 + 800 ppm NO and possessed good water resistance. Through the characterization of morphology and valence state of elements, uniform dispersion of the Cu-polyatomic clusters could directly visualize, which solved the defect of activity site agglomeration; therefore, a more low-temperature hydrogen-producing catalyst was obtained. This article provides a safer H2-SCR process on a coupling catalyst that simultaneously produces in-situ hydrogen and reduces NOx.

Variations of colour, polyphenol oxidase and peroxidase activities during the production of low temperature dried pasta in various durum wheat genotypes

SummaryThis research was conducted to determine the effect of milling and pasta making on yellow pigment content, soluble brown pigment content, polyphenol oxidase (PPO) activity and peroxidase (POD) activity in semolina and pasta derived from ten durum genotypes. Results showed that pasta colour was impacted more by the milling than by pasta making. The loss of yellow pigment content, POD activity, PPO activity and soluble brown pigment content due to milling was 1.3×, 4.4×, 6.2× and 17.5×, respectively, greater than losses due to pasta making. Dry pasta contained 62%, 31%, 16% and 25% of the original yellow pigment content, brown pigment content and PPO activity and POD activity in the grain, respectively. Semolina yellow pigment content had a positive effect on pasta colour while semolina protein content, ash content and speck count had negative effects. These results indicate the importance of selecting genotypes that have high yellow pigment content and excellent milling qualities.

Conductive Biomass Films Containing Graphene Oxide and Cationic Cellulose Nanofibers for Electric-Heating Applications.

A low-voltage biomass matrix and flexible electric-heating composite with graphene oxide (GO) and cationic cellulose nanofiber (CCNF) were fabricated by ultrasonic dispersion and suction filtration. The main results show that the tensile strength and strain of the films decreased with an increase in the GO content, but the thermal stability increased. The GO/CCNF film underwent rapid thermal decomposition at 250–350 °C, and the maximum degradation temperature was higher by 19 °C compared to that of the pure CCNF film. It was found that the electrical conductivity increased from 0.013 to 2.96 S/cm with an increase in the GO content from 20 to 60 wt%, resulting in an increase in the power density from 122 to 2456 W/m2. The films could rapidly attain the temperature within 50 s, and the heat transferred by radiation and convection was 21.62 mW/°C, thereby exhibiting excellent electric heating response. Moreover, the film demonstrated a stable electric-heating cycle after a 12.5 h cycling test and meets the requirements of low-temperature electric heating products under the 36 V electric safety limit, which expands the potential applications of biomass-derived cellulose nanofibers.

Low temperature production of biochars from different biomasses: Effect of static and rotary lab reactors and application as soil conditioners

Abundant renewable resources, such as biomass, can acquire added value when applied in industrial processes, such as slow pyrolysis to produce biochar. The type of biomass and the pyrolysis conditions are factors that determine the characteristics of the resulting biochars, influencing their potential applications. In this work, biochars were produced at 350 °C from sugarcane bagasse (SB), exhausted black wattle bark (EH), and elephant grass (EG). The materials were characterized considering the effects of different pyrolysis methods: (1) tube (laboratory scale), (2) rotary, and (3) muffle furnace (industrial scale). Despite using the same temperature, the formation of structures with condensed aromatic rings, the order of the processes that tended to form this type of structure was (3) ≥ (2) > (1). Pyrolysis method (3) tended to carbonize the constituents of biomass, than the other processes, which was promising for the production of biochar on an industrial scale. Besides, an investigation was made of the effects of applying BEG3 and BEH3 biochars as soil conditioners to mitigate emissions of N2O (a major greenhouse gas) and improve productivity in the cultivation of black oats. The BEG3 reduced the release of N2O from the soil, mainly affecting its peak emission, in addition to increasing the productivity of black oats by a factor of 1.22, compared to the control, being statistically significant results. It could be concluded that elephant grass biochar produced on an industrial scale is suitable for application to soils.

Expression and Characterization of a Thermostable Carrageenase From an Antarctic Polaribacter sp. NJDZ03 Strain.

The complete genome of Polaribacter sp. NJDZ03, which was isolated from the surface of Antarctic macroalgae, was analyzed by next-generation sequencing, and a putative carrageenase gene Car3206 was obtained. Car3206 was cloned and expressed in Escherichia coli BL21(DE3). After purification by Ni-NTA chromatography, the recombinant Car3206 protein was characterized and the antioxidant activity of the degraded product was investigated. The results showed that the recombinant plasmid pet-30a-car3206 was highly efficiently expressed in E. coli BL21(DE3). The purified recombinant Car3206 showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with an apparent molecular weight of 45 kDa. The optimum temperature of the recombinant Car3206 was 55°C, and it maintain 60–94% of its initial activity for 4–12 h at 55°C. It also kept almost 70% of the initial activity at 30°C, and more than 40% of the initial activity at 10°C. These results show that recombinant Car3206 had good low temperature resistance and thermal stability properties. The optimum pH of recombinant Car3206 was 7.0. Car3206 was activated by Na+, K+, and Ca2+, but was significantly inhibited by Cu2+ and Cr2+. Thin-layer chromatographic analysis indicated that Car3206 degraded carrageenan generating disaccharides as the only products. The antioxidant capacity of the degraded disaccharides in vitro was investigated and the results showed that different concentrations of the disaccharides had similar scavenging effects as vitamin C on , •OH, and DPPH•. To our knowledge, this is the first report about details of the biochemical characteristics of a carrageenase isolated from an Antarctic Polaribacter strain. The unique characteristics of Car3206, including its low temperature resistance, thermal stability, and product unity, suggest that this enzyme may be an interesting candidate for industrial processes.

Solar-driven low-temperature reforming of methanol into hydrogen via synergetic photo- and thermocatalysis

Low temperature and efficient hydrogen production from methanol is crucial in development of energy technology. Here a synergetic approach of photo- and thermocatalysis of coupling photocatalysis and thermocatalysis within the full spectrum is proposed to achieve efficient conversion of methanol to hydrogen. The composite copper/zinc/zirconium (Cu/Zn/Zr) oxide nanocatalysts are prepared and firstly utilized in synergetic photo- and thermocatalysis. Combine with the effect of the catalyst component and mass ratio on optical absorption, Cu/Zn/Zr (70:23:7) oxide nanocatalysts with full-spectrum absorption have best performance of synergetic photo- and thermocatalysis. Meanwhile, the synergetic photo- and thermocatalysis not only has better performance than either single photocatalysis or thermocatalysis, but also takes place at a relatively low temperature (130 °C). Under irradiation of 16 suns, the solar-chemical conversion efficiency reaches 45.6%. Photo-generated carriers further promote thermocatalysis, which explains the reaction mechanism of the synergetic photo- and thermocatalysis. The catalytic route in full spectrum can provide some references for future energy storage and utilization. • A novel approach of synergetic reforming of methanol into hydrogen is proposed. • The synergetic photo- and thermocatalysis utilizes full-spectrum solar energy. • The synergetic catalysis is superior to single either photocatalysis or thermocatalysis. • The proposed solar-driven reforming approach can be realized at 130 ℃.

Low-temperature pyrolysis products of waste cork and lignocellulosic biomass: product characterization

In recent years, there has been growing interest in the pyrolysis of biomass due to economic and environmental reasons. Low-temperature pyrolysis is one of the most straightforward and low-cost pyrolysis processes that may be used to produce added-value biochars as well as liquid and gas products from waste biomass. Lignocellulosic biomass obtained from the fractionation of Quercus cerris bark including cork-rich and phloem-rich granules were subjected to low-temperature pyrolysis (250–325 °C) and the resulting pyrolysis products were examined. The results showed that 59–90% biochar, 8–24% bio-oil, and 2–16% gas products could be obtained from the waste cork, while phloem results in 53–89% biochar, 8–21% bio-oil, and 3–30% gas. The produced chars are rich sources of calcium, magnesium, and potassium and these elements are concentrated in the char as the pyrolysis temperature increases. The pyrolysis condensates contain high amounts of lignin-derived phenolic compounds with 2-methoxy phenol being the most abundant compound.

Ultrafast green microwave-assisted synthesis of high-entropy oxide nanoparticles for Li-ion battery applications

In this study, a novel ultrafast facile green microwave-assisted method was developed for the synthesis of high-entropy oxide (HEO) (Mg, Cu, Ni, Co, Zn)O nanoparticles for the first time. The results indicated that all the five metallic elements were uniformly distributed in the single-phase rocksalt structure of the HEO nanoparticles. The particle-size distribution was within the range of 20–70 nm, with the average size of 44 nm. When used as anode materials for Li-ion batteries, the HEO nanoparticles exhibited remarkable lithium storage properties with the impressive stability as was demonstrated during 1000 cycles at 1 A/g. The exceptional advantages of the proposed method in this work, including ultrafast speed (few minutes), low temperature, nanoscale and high-purity products, and low cost, make it an excellent synthesis technique for application in newly developed high-entropy ceramics, particularly for Li-ion batteries.

Low-temperature hydrogen production from methanol over a ruthenium catalyst in water

Efficient conversion of methanol to hydrogen gas and formate with an appreciably high TOF and TON is achieved over the in situ generated ruthenium catalyst in water at low temperature.

An Al–Li alloy/water system for superior and low-temperature hydrogen production

A superior and low-temperature hydrogen supply technology based on the hydrolysis of an Al–Li alloy was developed.

Experimental Characterization of Tetrahydrofuran Low-Temperature Oxidation Products Including Ketohydroperoxides and Highly Oxygenated Molecules

The oxidation of tetrahydrofuran (THF) was carried out in a continuously jet-stirred tank reactor (JSR) at a total pressure of 10 atm, in fuel-lean conditions (equivalence ratio = 0.5), an initial fuel mole fraction of 5000 ppm, at a mean residence time of 2 s, and for temperatures ranging from 550 to 620 K. High-resolution mass spectrometry analyses was used to characterize low-temperature oxidation products of THF. MS analyses were performed using atmospheric pressure chemical ionizations in positive and negative modes. Both flow injection analyses and ultra-high-pressure liquid chromatography-MS/MS allowed characterizing a large set of chemicals including hydroperoxides and diols (C 4 H 8 O 3), ketohydroperoxides (C 4 H 6 O 4), and more oxygenated molecules (up to C 4 H 8 O 7) resulting from up to three oxygen molecules addition of on α and β THF radicals. The existence of-OH or-OOH groups in the products was confirmed by hydrogen-deuterium exchange using D 2 O. We detected 24 products with molecular weight of 40-168, not reported in previous studies. Simulations using the latest THF oxidation chemical kinetic reaction mechanism available from the literature were compared to the present measurements of ketohydroperoxides and other products of THF cool flame. The kinetic scheme represented well the present qualitative data.

The influence of temperature on filtration performance and fouling during cold microfiltration of skim milk

Changes in the physicochemical properties and distribution of constituents in skim milk during microfiltration (MF) at low temperature influence filtration performance and product composition. In this study, the influence of processing temperature within the cold MF range (4, 8 and 12 °C) on filtration performance, fouling and partitioning of proteins was investigated. MF at 4 °C required the greatest energy input due to the significantly higher (p < 0.05) viscosity of feed and retentate streams, compared to processing at 8 and 12 °C. The greatest and lowest extents of reversible and irreversible fouling during MF were observed on filtration at 12 and 4 °C, respectively. Chemical analysis of the cleaning solutions post-processing demonstrated that protein was the major foulant; the lowest protein content in the recovered cleaning solutions (50 °C water and 55 °C alkali) was measured after MF at 4 °C. The concentration of β-casein, β-lactoglobulin and α-lactalbumin in the permeate all decreased throughout MF, due to fouling of the membrane. The greatest decrease in concentration of β-casein in the permeate during MF was observed at 12 °C (18.1%) followed by 8 °C (17.1%) and 4 °C (13.6%). The results of this study provide valuable information on processing efficiency (i.e., energy consumption and protein yield) and membrane fouling during the processing of skim milk in the cold MF range.

A System Design for Large Scale Production of Elemental Boron by Electrochemical Deposition

In this study, a new electrolysis melt reactor for large-scale and low-temperature production amorphous elemental boron powders (ABP) equipped with a rotating star cathode electrode in a graphite crucible, which decreases the homogenization time of the boron salts is reported. The electrochemical deposition system has designed to produce high-purity ABP up to 25 kg capacity for a different combination of various salts in different percentage ranges in accordance with commercial production. One of the innovations of the system, the star type iron cathode is rotated bidirectionally and positioned up and down when desired, thanks to the movement transmission shaft. After the design of the melted reactor, ABP has produced using certain proportions of KCl, KBF4, and B2O3 salts. As a result, the melting time of KCl, KBF4, and B2O3 mixed salts was 3.7 h, and the production took place at a low temperature of 480 degrees. The highest cathode current density in production was measured as 1.083 A cm−2. The analyses revealed that an amorphous structured high purity (95.6%) elemental boron (B) particles were produced. The morphology and chemical composition of the highest purity B has characterized using XRD, SEM, EDS, and FTIR analysis.

Biomass-formic acid-hydrogen conversion process with improved sustainability and formic acid yield: Combination of citric acid and mechanocatalytic depolymerization

Sustainable and efficient hydrogen production from biomass resources have been highly desired. Here, we report a low-temperature hydrogen production process from lignocellulosic biomass passing through formic acid (the biomass-formic acid-hydrogen conversion process) with improved sustainability and formic acid yield. In the biomass oxidation/hydrolysis step, toxic sulfuric acid has been replaced by sustainable citric acid. In addition, mechanocatalytic depolymerization of biomass has been applied to the biomass pretreatment step, resulting in the remarkable improvement in formic acid yield. In the first step, the citric-acid-impregnated biomass was subjected to a mechanocatalytic depolymerization process for facilitating contact between the substrate and catalysts (MD-CIB). In the second step, the crude formic acid (CF) solution was obtained via combined hydrolysis-oxidation process of the MD-CIB in the presence of dimethyl sulfoxide (DMSO), and hydrogen peroxide (H2O2). The yield of formic acid were measured up to be 50.03%. In the third step, the lignin-free crude formic acid (LCF) solution was recovered by filtration, or distilled formic acid (DF) solution was obtained by distillation of the CF solution. In the final step, hydrogen was generated from LCF or DF solutions through dehydrogenation of formic acid over Pd catalysts supported on amine-functionalized mesoporous silica (KIE-6) with a sodium formate. The turnover frequency (TOF) at 10 min were measured up to be 279.24 mol H2 mol Pd-1h−1. The clean hydrogen, which is produced from biomass passing through formic acid, could be directly applied in fuel cell as an energy source. Our hydrogen production process is expected to be much more efficient, sustainable and economical process for hydrogen production from biomass. In addition, organic acids as a byproduct could be utilized as a platform chemical.

Low-temperature mobility-lifetime product in synthetic diamond

The mobility-lifetime (μτ) product is an important parameter that determines the performance of electronic and photonic devices. To overcome the previously reported difficulties in measuring the μτ product at cryogenic temperatures, we implement a time-resolved cyclotron resonance method to determine the carrier lifetime τ. After clarifying the difference between the AC and DC mobilities measured by cyclotron resonance and time-of-flight methods, respectively, we demonstrate an inverse temperature dependence of the μτ product. The highest recorded μτ product of 0.2 cm2/V, which is approximately 100 times the room-temperature value, was obtained at 2 K for chemical-vapor-deposition diamond of the highest currently available purity.

Editors’ Choice—Economic Considerations for Low-Temperature Electrochemical Ammonia Production: Achieving Haber-Bosch Parity

Production of ammonia through coupling renewable energy with electrolysis cells will undoubtedly aid in reducing carbon dioxide emissions from the ammonia production industry. However, if the cost for electrochemical routes does not reach a Haber-Bosch parity point, then it is unlikely that electrochemical ammonia synthesis will become industrially viable. This promotes a strong need for analyses that explore the economics of various system designs and production scales, to assess what systems and scales can attain Haber-Bosch price parity. Here, we aim to define the Haber-Bosch parity targets for various production scales. We then explore the economic considerations for two electrochemical systems for ammonia synthesis. The first system contains a single electrolysis cell where nitrogen and water are the sole reactants. The second system explores a two-staged electrolysis system. The first stage consists of a water electrolysis cell where water serves as the reactant and hydrogen and oxygen are the products. The second stage consists of a nitrogen electrolysis cell where the reactants are nitrogen and hydrogen and ammonia is the product. We emphasize the important role production scale plays in meeting Haber-Bosch price parity, and highlight the key challenges for electrochemical ammonia production.

Experimental characterization of n-heptane low-temperature oxidation products including keto-hydroperoxides and highly oxygenated organic molecules (HOMs)

The oxidation of n-heptane was performed in a jet-stirred reactor (JSR) at 10 atm, an equivalence ratio of 0.5, and an initial fuel concentration of 1000 ppm at a residence time of 1 s in the temperature range 580–790 K (from cool-flame, negative temperature coefficient NTC, to intermediate temperature oxidation regime), and with 5000 ppm of fuel at 647 K and a residence time of 1.5 s. Low-temperature products formed in JSR were characterized using high-resolution mass spectrometry analyses (HRMS). Atmospheric pressure chemical ionizations (APCI) was used in positive and negative modes for MS analyses. Both flow injection analyses (FIA) or ultra-high-pressure liquid chromatography-OrbitrapⓇ coupling were used to characterize hydroperoxides (C7H16O2), keto-hydroperoxides (C7H14O3), cyclic ethers (C7H14O), carboxylic acids (C2H4O2, C3H6O2, C4H8O2), ketones (C3–5H6–10O), diones (C7H12O2), and highly oxygenated molecules (C7H14O5, C7H14O7, C7H14O9, C7H14O11) resulting from the addition of up to six O2 molecules on fuel radicals. H/D exchange with D2O was used to confirm the presence of –OH or –OOH groups in the products. Several available kinetic reaction mechanisms were tested against the present measurements of keto-hydroperoxides showing significant discrepancies.