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81.
Ken’ichiro Matsumoto Takehiro Okei Inori Honma Toshihiko Ooi Hirobumi Aoki Seiichi Taguchi 《Applied microbiology and biotechnology》2013,97(1):205-210
(R)-3-hydroxybutyrate [(R)-3HB] is a useful precursor in the synthesis of value-added chiral compounds such as antibiotics and vitamins. Typically, (R)-3HB has been microbially produced from sugars via modified (R)-3HB-polymer-synthesizing pathways in which acetyl CoA is converted into (R)-3-hydroxybutyryl-coenzyme A [(R)-3HB-CoA] by β-ketothiolase (PhaA) and acetoacetyl CoA reductase (PhaB). (R)-3HB-CoA is hydrolyzed into (R)-3HB by modifying enzymes or undergoes degradation of the polymerized product. In the present study, we constructed a new (R)-3HB-generating pathway from glucose by using propionyl CoA transferase (PCT). This pathway was designed to excrete (R)-3HB by means of a PCT-catalyzed reaction coupled with regeneration of acetyl CoA, the starting substance for synthesizing (R)-3HB-CoA. Considering the equilibrium reaction of PCT, the PCT-catalyzed (R)-3HB production would be expected to be facilitated by the addition of acetate since it acts as an acceptor of CoA. As expected, the engineered Escherichia coli harboring the phaAB and pct genes produced 1.0 g?L?1 (R)-3HB from glucose, and with the addition of acetate into the medium, the concentration was increased up to 5.2 g?L?1, with a productivity of 0.22 g?L?1 h?1. The effectiveness of the extracellularly added acetate was evaluated by monitoring the conversion of 13C carbonyl carbon-labeled acetate into (R)-3HB using gas chromatography/mass spectrometry. The enantiopurity of (R)-3HB was determined to be 99.2% using chiral liquid chromatography. These results demonstrate that the PCT pathway achieved a rapid co-conversion of glucose and acetate into (R)-3HB. 相似文献
82.
Masajiro Kibi Hiroshi Yoshino Kin’ichiro Sakaguchi 《Bioscience, biotechnology, and biochemistry》2013,77(9):693-701
5′-Phosphodiesterase, which degrades RNA into nucleoside-5′-monophosphates but does not attack DNA, is present not only in mycelium but also in culture filtrate of Penicillium citrinum Thorn 1131. For the formation of this enzyme pH of the culture medium must be kept below 7.0 during culture, as this enzyme is inactivated rapidly in alkaline solution. The pH optimum of this enzyme is in the region of pH 5. Cysteine, Mg++, sodium fluoride, and inorganic ortho- or pyrophosphate are without appreciable effect on this enzyme. Nucleoside-5′-monophosphates, which have been regarded as new chemical seasonings, can be produced economically in a large scale by using the microbial 5′-phosphodiesterase. 相似文献
83.
Han X Satoh Y Satoh T Matsumoto K Kakuchi T Taguchi S Dairi T Munekata M Tajima K 《Applied microbiology and biotechnology》2011,92(3):509-517
A previously established improved two-phase reaction system has been applied to analyze the substrate specificities and polymerization
activities of polyhydroxyalkanoate (PHA) synthases. We first analyzed the substrate specificity of propionate coenzyme A (CoA)
transferase and found that 2-hydroxybutyrate (2HB) was converted into its CoA derivative. Then, the synthesis of PHA incorporating
2HB was achieved by a wild-type class I PHA synthase from Ralstonia eutropha. The PHA synthase stereoselectively polymerized (R)-2HB, and the maximal molar ratio of 2HB in the polymer was 9 mol%. The yields and the molecular weights of the products
were decreased with the increase of the (R)-2HB concentration in the reaction mixture. The weight-average molecular weight of the polymer incorporating 9 mol% 2HB was
1.00 × 105, and a unimodal peak with polydispersity of 3.1 was observed in the GPC chart. Thermal properties of the polymer incorporating
9 mol% 2HB were analyzed by DSC and TG-DTA. T
g, T
m, and T
d (10%) were observed at −1.1°C, 158.8°C, and 252.7°C, respectively. In general, major components of PHAs are 3-hydroxyalkanoates,
and only engineered class II PHA synthases have been reported as enzymes having the ability to polymerize HA with the hydroxyl
group at C2 position. Thus, this is the first report to demonstrate that wild-type class I PHA synthase was able to polymerize
2HB. 相似文献
84.
Goro Hanya Pablo Stevenson Maria van Noordwijk Siew Te Wong Tomoko Kanamori Noko Kuze Shin‐ichiro Aiba Colin A. Chapman Carel van Schaik 《Ecography》2011,34(6):1009-1017
We examine the effect of total annual food abundance and seasonal availability on the biomass and species richness for frugivorous primates on three continents (n=16 sites) by data on fruit fall. We reveal that the best‐fit models for predicting primate biomass include total annual fruit fall (positive), seasonality (negative) and biogeography (Old World>New World and mainland>island) and that these factors explain 56–67% of the variation. For the number of species, the best‐fit models include seasonality (negative) and biogeography (Old World>New World and mainland>island) but not total annual fruit fall. Annual temperature has additional effects on primate biomass when the effects of fruits and biogeography are controlled, but there is no such effect on species richness. The present results indicate that, measured on local scales, primate biomass and number of species is affected by the seasonal variation in food availability. 相似文献
85.
A new species of a chlorarachniophyte alga, Bigelowiella longifila sp. nov., is described. It is classified as a member of Bigelowiella as flagellate cells constitute the main stage of the life cycle. However, this alga is different from the only described species of the genus, B. natans Moestrup, in having a unique amoeboid stage in the life cycle. We observed an interesting behavior of amoeboid daughter cells after cell division: One of the two daughter cells inherits the long filopodium of the parental cell, and it subsequently transports its cell contents through the filopodium to develop at its opposite end. The other daughter cell forms a new filopodium. This unequal behavior of daughter cells may have evolved before the chlorarachniophytes and some colorless cercozoans diverged. 相似文献
86.
The nucleomorph genome size of the recently described chlorarachniophyte Partenskyella glossopodia, which forms an independent lineage in the phylogeny of chlorarachniophytes, was analyzed by pulse‐field gel electrophoresis and Southern hybridization. These analyses showed that the nucleomorph genome of P. glossopodia is composed of three linear chromosomes that are about 445 kbp, 313 kbp, and 275 kbp in size. Thus, the total genome size is approximately 1033 kbp, which is significantly larger than the known size of chlorarachniophyte nucleomorph genomes, i.e. 330–610 kbp. This is the first study to report a nucleomorph genome that reaches approximately 1 Mbp in size. 相似文献
87.
A chlorarachniophycean alga, Lotharella amoebiformis, which has been classified in the genus Lotharella is placed into a new genus Amorphochlora gen. nov., based on its phylogenetic position, which has been clarified by the recently accumulated molecular phylogenetic information, and the morphological difference between the vegetative cells of the Lotharella species. Following this taxonomic treatment, a new combination Amorphochlora amoebiformis comb. nov., is proposed. 相似文献
88.
Takuya Miyake Jun Nakajima Norio Onikura Shigetoyo Ikemoto Kei��ichiro Iguchi Akira Komaru Kouichi Kawamura 《Conservation Genetics》2011,12(2):383-400
Rhodeus atremius is an endemic bitterling fish from Japan comprising two endangered subspecies, R. a. atremius and R. a. suigensis. The latter subspecies, which had dramatically declined in last decades, was reported to contain two distinct mtDNA lineages. In order to estimate the optimized units for conservation management, the genetic structure of R. atremius was inferred by analyzing mtDNA and microsatellite markers (MS). Allelic richness and heterozygosity of MS in R. a. suigensis was less than half that in R. a. atremius. In R. a. suigensis, not only within-population genetic diversity but also among-population genetic divergence was low, with the exception of population Ah1, while the diversity was high and the divergence showed isolation by distance in R. a. atremius. In mtDNA and MS, R. a. suigensis concordantly formed a single lineage, while R. a. atremius encompassed four mtDNA lineages, two of which were completely admixed into one group on the basis of MS. In population Ah1 a striking introgression between the two subspecies was suggested by a Bayesian-based assignment test, with the presence of mtDNA haplotype of R. a. atremius. Contrary to the prevailing theory, R. a. suigensis corresponds to a single conservation unit, while three units seem appropriate for R. a. atremius. In addition, low genetic diversity of R. a. suigensis might have arisen mainly as a result of recent bottlenecks before population fragmentation, followed by current anthropogenic effects. Genetic introgression in population Ah1 was probably the result of human transplantation of R. a. atremius. 相似文献
89.
Song Y Matsumoto K Yamada M Gohda A Brigham CJ Sinskey AJ Taguchi S 《Applied microbiology and biotechnology》2012,93(5):1917-1925
The first biosynthetic system for lactate (LA)-based polyesters was previously created in recombinant Escherichia coli (Taguchi et al. 2008). Here, we have begun efforts to upgrade the prototype polymer production system to a practical stage by using metabolically
engineered Gram-positive bacterium Corynebacterium glutamicum as an endotoxin-free platform. We designed metabolic pathways in C. glutamicum to generate monomer substrates, lactyl-CoA (LA-CoA), and 3-hydroxybutyryl-CoA (3HB-CoA), for the copolymerization catalyzed
by the LA-polymerizing enzyme (LPE). LA-CoA was synthesized by D-lactate dehydrogenase and propionyl-CoA transferase, while 3HB-CoA was supplied by β-ketothiolase (PhaA) and NADPH-dependent
acetoacetyl-CoA reductase (PhaB). The functional expression of these enzymes led to a production of P(LA-co-3HB) with high LA fractions (96.8 mol%). The omission of PhaA and PhaB from this pathway led to a further increase in LA
fraction up to 99.3 mol%. The newly engineered C. glutamicum potentially serves as a food-grade and biomedically applicable platform for the production of poly(lactic acid)-like polyester. 相似文献
90.
The classic model of Smith and Fretwell predicts that the optimal egg size will vary according to the shape of the relationship
between offspring size and offspring fitness, which may vary among environments. Adaptive significance of intrapopulation
egg size variation was examined using Ayu (Plecoglossus altivelis). The species has an annual and migratory life history. Fish under controlled rearing conditions become sexually mature with
a trend that smaller females produced larger eggs later in the season. Observed egg size variation was explained by the maternal
specific growth rate, which was composed of maternal body size and growing period. Hatchlings from larger eggs had a larger
notochord length, larger yolk-sac and grew faster. Such offspring traits provide general advantages of increased larval size,
which confer competitive ability for assuring early survivorship. In conclusion, egg size plasticity in Ayu suggests higher
offspring fitness through enhancement of their accessibility to food. 相似文献