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.
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
Uridine diphosphate N-acetylglucosamine (UDPAG) can be produced by chemical, enzymatic, chemoenzymatic, and fermentative methods. In this study,
we used whole-cell catalysis method to produce UDPAG for the first time by Saccharomyces cerevisiae. In order to increase the ATP utilization efficiency and UDPAG conversion yield, the response surface methodology was applied
to optimize the whole-cell catalytic conditions for UDPAG production. Firstly, effects of uridine 5′-monophosphate (5′-UMP),
glucosamine, vitamin B1, glycerol, magnesium chloride, potassium chloride, temperature, sodium dihydrogen phosphate, sodium
acetate, fructose, and pH on UDPAG production were evaluated by a fractional factorial design. Results showed that UDPAG production
was mainly affected by sodium dihydrogen phosphate, temperature, and vitamin B1. Then, the concentrations of sodium dihydrogen
phosphate and vitamin B1 and temperature were further investigated with a central composite design and response surface analysis.
The cultivation conditions to obtain the optimal UDPAG production were determined: sodium dihydrogen phosphate, 31.2 g/L;
temperature, 29°C, and vitamin B1, 0.026 g/L. This optimization strategy led to an enhancement of UDPAG production from 2.51
to 4.25 g/L, yield from 44.6% to 75.6% based on the initial 5′-UMP concentration, and ATP utilization efficiency from 7.43%
to 12.6%. 相似文献
Uncoupling proteins (UCPs) are mitochondrial membrane transporters, acting as an uncoupler in oxidative phosphorylation. In this study, we designed 11 primer sets based on the human and mouse UCP2, UCP3 sequences and successfully amplified full regions of porcine UCP2 and UCP3 by polymerase chain reactions (PCR). Comparison of the UCP2 and UCP3 genic structures revealed a highly conservative region was putatively presented, showing the second transmembrane domain may be the UCPs' cardinal function region. Altogether 23 nucleotide polymorphisms of UCP2 and UCP3 genes were discovered in Yorkshire, Wuzhishan, and Lepinghua pigs. These polymorphisms included 3 missense mutations, 16 intronic substitutions, and 4 intronic deletions. The substitution of Ala-55-Val in UCP2 is actually the most common mutation in human. We also calculated genotypic frequencies of five polymorphisms in three pig breeds. 相似文献