Ionic liquid pretreatment of biomass has been shown to greatly reduce the recalcitrance of lignocellulosic biomass, resulting in improved sugar yields after enzymatic saccharification. However, even ...under these improved saccharification conditions the cost of enzymes still represents a significant proportion of the total cost of producing sugars and ultimately fuels from lignocellulosic biomass. Much of the high cost of enzymes is due to the low catalytic efficiency and stability of lignocellulolytic enzymes, especially cellulases, under conditions that include high temperatures and the presence of residual pretreatment chemicals, such as acids, organic solvents, bases, or ionic liquids. Improving the efficiency of the saccharification process on ionic liquid pretreated biomass will facilitate reduced enzyme loading and cost. Thermophilic cellulases have been shown to be stable and active in ionic liquids but their activity is typically at lower levels. Cel5A_Tma, a thermophilic endoglucanase from Thermotoga maritima, is highly active on cellulosic substrates and is stable in ionic liquid environments. Here, our motivation was to engineer mutants of Cel5A_Tma with higher activity on 1-ethyl-3-methylimidazolium acetate (C2mimOAc) pretreated biomass. We developed a robotic platform to screen a random mutagenesis library of Cel5A_Tma. Twelve mutants with 25-42% improvement in specific activity on carboxymethyl cellulose and up to 30% improvement on ionic-liquid pretreated switchgrass were successfully isolated and characterized from a library of twenty thousand variants. Interestingly, most of the mutations in the improved variants are located distally to the active site on the protein surface and are not directly involved with substrate binding.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Smart system employed CO
2
gas as new trigger has been attracting enormous attention in recent years, but few monomers that are capable of switching their hydrophobicity/hydrophility upon CO
2
...stimulation have been reported. A novel CO
2
responsive monomer, 4-vinylbenzyl amidine, is designed and synthesized in this work with N,N-dimethylacetamide dimethyl acetal and 4-vinylbenzyl amine that is prepared through the Gabriel reaction. In bi-phase solvent of n-hexane and water, the monomer dissolves in n-hexane first and then transforms into water upon the CO
2
treatment, indicating a hydrophobic to hydrophilic transition. This transformation is demonstrated as reversible by monitoring the conductivity variation of its wet dimethyl formamide solution during alternate bubbling/removing CO
2
. The protonation of 4-vinylbenzyl amidine upon CO
2
treatment is demonstrated by
1
H NMR which also accounts for the dissolubility change. The reversible addition-fragmentation chain-transfer polymerization of this monomer is also performed, finding the reaction only occurs in glacial acetic acid. The reason can be ascribed to the different radical structure produced in different solvent.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
People in northern and western China were probably the first in the world to use coal as a source of energy in a consistent way. The ages cluster around 1900–2200 bc in modern day Inner Mongolia and ...Shanxi provinces. These are areas where near-surface coal is abundant today and woody vegetation was scant in the Bronze Age. Since coal is bulky to transport, it was probably not a cost-effective energy source in areas with abundant wood supply. The sites where coal was first used were probably occupied for a century to a few centuries at most and were associated with Bronze Age societies. The earliest age is about 3490 bc from a house site at Xiahe in Shaanxi Province; however, the coal is not securely tied to the radiocarbon ages and is assumed to have been used at this site sometime after 3490 bc. The elemental composition of modern mine and sedimentary coal in nearby archaeological contexts suggests that coal was used from local sources, and that elemental composition of coal may be a useful tool in identifying site origin of coal.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Moringa (
Moringa oleifera
) seed oil is an edible vegetable oil rich in unsaturated fatty acids. In this study, the supercritical CO
2
fluid extraction method was employed to obtain the maximum ...yield of moringa seed oil. The effects of temperature, time, and pressure, three characteristics of extractions, on the extraction rate of Moringa seed oil were investigated by single factor test and response surface methodological approach. The optimal process conditions of supercritical CO
2
fluid extraction of moringa seed oil were determined as extraction temperature of 45°C, extraction time of 2.5 h, extraction pressure of 50 MPa, and CO
2
flow rate of 240 L/h, resulting in a maximum yield of 38.54%. Composition analysis shows that the extracted moringa seed oil is rich in unsaturated fatty acids, including oleic acid, octadecanoic acid, palmitic acid, stearic acid, eicosanoic acid, etc. Furthermore, we found that Moringa seed oil exerted potent antioxidant activities on DPPH and hydroxyl radicals, and its efficacy was comparable to commercial peanut oil and tea oil. Overall, this novel extraction method of moringa seed oil may increase its potential value and application in the food and nutraceutical industries.
Abstract
Noble gases in lunar soils provide critical information regarding solar wind and cosmic-ray interactions with the lunar surface, as well as the history of impact events affecting the ...regolith turnover processes. Here, we studied the characteristics of noble gases He, Ne, Ar in Chang’E-5 soil. High
4
He/
36
Ar and
20
Ne/
36
Ar values show that the soil has typical mare terrain characteristics. Furthermore, both values are higher than those in other lunar soils, suggesting the secondary processes occurring in the soil may have been less strong than in other lunar samples. Trapped (
3
He/
4
He)
tr
and (
20
Ne/
22
Ne)
tr
values were less fractionated than those of Apollo soils, also indicating the weak secondary processes the Chang’E-5 soil underwent. Trapped (
40
Ar/
36
Ar)
tr
values indicate the implanted solar wind was young. The integrated exposure times to solar wind of the soil on the lunar surface suggest the Chang’E-5 soil was not seriously admixed by sputtered material from nearby rocks.
In recent years, the low-carbon city pilot policy has been important work in China. It aims to control the city's greenhouse gas emissions, find a "win-win" path of low-carbon and economy and drive ...the innovation and development of cities through low-carbon goals. In this context, we consider the low-carbon city pilot policy as the starting point. Based on the data of A-share listed companies in Shanghai and Shenzhen from 2005 to 2015 in 285 prefecture-level cities, the OP and LP methods are used to calculate total factor productivity (TFP). In this paper, using PSM-DID and other methods, we empirically test whether and how the low-carbon city pilot policy affects enterprise TFP. The results indicate that the construction of low-carbon cities significantly promotes an increase in the TFP of local enterprises. In addition, improving technological innovation and optimizing the efficiency of resource allocation are two important transmission mechanisms. The above conclusions are robust to a series of tests. Therefore, the implementation of a low-carbon city pilot policy can help achieve the "win-win" goal of emission reduction and high-quality enterprise development. This study provides strong support for further expanding the scope of low-carbon city pilot policy projects and the scientific implementation of climate change policies, and it provides beneficial policy enlightenment for the scientific implementation of urban emission reduction control to win the battle against climate change.
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