An NADPH-dependent carbonyl reductase (PsCR) gene from Pichia stipitis was cloned. It contains an open reading frame of 849 bp encoding 283 amino acids whose sequence had less than 60% identity
to known reductases that produce ethyl (S)-4-chloro-3-hydroxybutanoates (S-CHBE). When expressed in Escherichia coli, the recombinant PsCR exhibited an activity of 27 U/mg using ethyl 4-chloro-3-oxobutanoate (COBE) as a substrate. Reduction
of COBE to (S)-CHBE by transformants in an aqueous mono-phase system for 18 h, gave a molar yield of 94% and an optical purity of the (S)-isomer of more than 99% enantiomeric excess. 相似文献
Microbial nuclease P1 from Penicllium citrinum was immobilized on macroporous absorbent resins: strong polar poly (styrene-co-DVB) resin (SPPSD), polymethacrylic ester resin and poly (styrene-co-DVB)-Br resin. The results showed that SPPSD was the best carrier. Three methods of glutaraldehyde cross-linking were used and simultaneous immobilization and cross-linking (CIS) was demonstrated to be the best method. The functional properties of immobilized nuclease P1 were studied and compared to those of the free enzyme. The highest enzyme activities of free and immobilized nuclease P1 were obtained in 0.2 M acetate buffer at pH 4.5 and a temperature of 70 °C. An increase in Km (from 3.165 to 18.125 mg mL?1) and a decrease in Vmax (from 1667.18 to 443.95 U min?1 mL?1) were recorded after immobilization. SPPSD-glutaraldehyde-nuclease P1 exhibited better thermal stability than the free enzyme. The apparent activation energy (Ea) of the free and immobilized nuclease P1 was 137.04 kJ mol?1 and 98.43 kJ mol?1, respectively, implying that the catalytic efficiency of the immobilized enzyme was restricted by mass-transfer rather than kinetic limit. 相似文献
Aim, Scope, and Background Studies to evaluate the energy and emission impacts of vehicle/fuel systems have to address allocation of the energy use and
emissions associated with petroleum refineries to various petroleum products because refineries produce multiple products.
The allocation is needed in evaluating energy and emission effects of individual transportation fuels. Allocation methods
used so far for petroleum-based fuels (e.g., gasoline, diesel, and liquefied petroleum gas [LPG]) are based primarily on mass,
energy content, or market value shares of individual fuels from a given refinery. The aggregate approach at the refinery level
is unable to account for the energy use and emission differences associated with producing individual fuels at the next sub-level:
individual refining processes within a refinery. The approach ignores the fact that different refinery products go through
different processes within a refinery. Allocation at the subprocess level (i.e., the refining process level) instead of at
the aggregate process level (i.e., the refinery level) is advocated by the International Standard Organization. In this study,
we seek a means of allocating total refinery energy use among various refinery products at the level of individual refinery
processes.
Main Features We present a petroleum refinery-process-based approach to allocating energy use in a petroleum refinery to petroleum refinery
products according to mass, energy content, and market value share of final and intermediate petroleum products as they flow
through refining processes within a refinery. The approach is based on energy and mass balance among refining processes within
a petroleum refinery. By using published energy and mass balance data for a simplified U.S. refinery, we developed a methodology
and used it to allocate total energy use within a refinery to various petroleum products. The approach accounts for energy
use during individual refining processes by tracking product stream mass and energy use within a refinery. The energy use
associated with an individual refining process is then distributed to product streams by using the mass, energy content, or
market value share of each product stream as the weighting factors.
Results The results from this study reveal that product-specific energy use based on the refinery process-level allocation differs
considerably from that based on the refinery-level allocation. We calculated well-to-pump total energy use and greenhouse
gas (GHG) emissions for gasoline, diesel, LPG, and naphtha with the refinery process-based allocation approach. For gasoline,
the efficiency estimated from the refinery-level allocation underestimates gasoline energy use, relative to the process-level
based gasoline efficiency. For diesel fuel, the well-to-pump energy use for the process-level allocations with the mass- and
energy-content-based weighting factors is smaller than that predicted with the refinery-level allocations. However, the process-level
allocation with the market-value-based weighting factors has results very close to those obtained by using the refinery-level
allocations. For LPG, the refinery-level allocation significantly overestimates LPG energy use. For naphtha, the refinery-level
allocation overestimates naphtha energy use. The GHG emission patterns for each of the fuels are similar to those of energy
use.
Conclusions We presented a refining-process-level-based method that can be used to allocate energy use of individual refining processes
to refinery products. The process-level-based method captures process-dependent characteristics of fuel production within
a petroleum refinery. The method starts with the mass and energy flow chart of a refinery, tracks energy use by individual
refining processes, and distributes energy use of a given refining process to products from the process. In allocating energy
use to refinery products, the allocation method could rely on product mass, product energy contents, or product market values
as weighting factors. While the mass- and energy-content-based allocation methods provide an engineering perspective of energy
allocation within a refinery, the market-value-based allocation method provides an economic perspective. The results from
this study show that energy allocations at the aggregate refinery level and at the refining process level could make a difference
in evaluating the energy use and emissions associated with individual petroleum products. Furthermore, for the refining-process-level
allocation method, use of mass — energy content- or market value share-based weighting factors could lead to different results
for diesel fuels, LPG, and naphtha. We suggest that, when possible, energy use allocations should be made at the lowest subprocess
level — a confirmation of the recommendation by the International Standard Organization for life cycle analyses.
Outlook The allocation of energy use in petroleum refineries at the refining process level in this study follows the recommendation
of ISO 14041 that allocations should be accomplished at the subprocess level when possible. We developed a method in this
study that can be readily adapted for refineries in which process-level energy and mass balance data are available. The process-level
allocation helps reveal some additional energy and emission burdens associated with certain refinery products that are otherwise
overlooked with the refinery-level allocation. When possible, process-level allocation should be used in life-cycle analyses. 相似文献
Particle size of lignocellulose materials is an important factor for enzymatic hydrolysis efficiency. In this study, corn stover was milled and sieved into different size fractions from 1.42, 0.69, 0.34, to 0.21 mm, and the corresponding enzymatic hydrolysis yields were 24.69, 23.96, 25.34, and 26.97 %, respectively. The results indicate that the hydrolysis yield is approximately constant with changing corn stover particle sizes in the experimental range. The overall surface area and the inner pore size measurement show that the overall specific surface area was less than 2 % with the half reduction of particle size due to the greater inner pore surface area. The scanning electron microscope photographs gave direct evidence of the much greater inner pore surface area of corn stover particles. This result provided a reference when a proper size reduction of lignocellulose materials is considered in biorefining operations. 相似文献
Phellodendron chinense Schneid is an important Chinese herb with berberine and phellodendrine in stems and leaves, but with little information available on in vitro culture of this species. Disinfection of explants in 75% alcohol for 45 s, sterilization in 0.1% HgCl2 for 20 min, and submersion in 1.0 mol L−1 gibberellin3 (GA3) solution for 24 h was the optimal condition for seed germination. Murashige and Skoog’s (MS) medium supplemented with 2.0 mg L−1 6-benzylaminopurine (6-BA) in combination with 1.5 mg L−1 1-naphthylacetic acid (NAA) was optimal for callus induction. MS medium supplemented with 2.0 mg L−1 6-BA was the appropriate medium for induction of adventitious shoots, and 1/2MS medium supplemented with 2.0 mg L−1 indole-3-butytric acid (IBA) and 0.5% active carbon was the optimal medium for root induction. The 15-d survival rate of regenerated plantlets after transplanting to basins containing perlite and peat moss (1:4) was greater than 80%, and the berberine and phellodendrine accumulation was lower in callus compared with regenerated plantlets. The establishment of highly efficient regeneration system provides technical support for genetic breeding of Phellodendron chinense Schneid.