共查询到20条相似文献,搜索用时 15 毫秒
1.
Sebastián Sánchez Vicente Bravo Juan Francisco García Nicolás Cruz Manuel Cuevas 《World journal of microbiology & biotechnology》2008,24(5):709-716
The fermentation of d-glucose and d-xylose mixtures by the yeast Candida tropicalis NBRC 0618 has been studied under the most favourable operation conditions for the culture, determining the most adequate
initial proportion in these sugars for xylitol production. In all the experiments a synthetic culture medium was used, with
an initial total substrate concentration of 25 g L−1, a constant pH of 5.0 and a temperature of 30 °C. From the experimental results, it was deduced that the highest values of
specific rates of production and of overall yield in xylitol were achieved for the mixtures with the highest percentage of
d-xylose, specifically in the culture with the initial d-glucose and d-xylose concentrations of 1 and 24 g L−1, respectively, with an overall xylitol yield of 0.28 g g−1. In addition, the specific rates of xylitol production declined over the time course of the culture and the formation of
this bioproduct was favoured by the presence of small quantities of d-glucose. The sum of the overall yield values in xylitol and ethanol for all the experiments ranged from 0.26 to 0.56 g bioproduct/g
total substrate. 相似文献
2.
M. Helanto K. Kiviharju T. Granström M. Leisola A. Nyyssölä 《Applied microbiology and biotechnology》2009,83(1):77-83
l-Ribose is a rare and expensive sugar that can be used as a precursor for the production of l-nucleoside analogues, which are used as antiviral drugs. In this work, we describe a novel way of producing l-ribose from the readily available raw material l-arabinose. This was achieved by introducing l-ribose isomerase activity into l-ribulokinase-deficient Escherichia coli UP1110 and Lactobacillus plantarum BPT197 strains. The process for l-ribose production by resting cells was investigated. The initial l-ribose production rates at 39°C and pH 8 were 0.46 ± 0.01 g g−1 h−1 (1.84 ± 0.03 g l−1 h−1) and 0.27 ± 0.01 g g−1 h−1 (1.91 ± 0.1 g l−1 h−1) for E. coli and for L. plantarum, respectively. Conversions were around 20% at their highest in the experiments. Also partially purified protein precipitates
having both l-arabinose isomerase and l-ribose isomerase activity were successfully used for converting l-arabinose to l-ribose. 相似文献
3.
To construct Candida tropicalis strains that produce a high yield of xylitol with no requirement for co-substrates, we engineered the yeast with an attenuated
xylitol dehydrogenase (XDH) and then assessed the efficiency of xylitol production The mutants, strains XDH-5 (with only one
copy of the XDH gene), and ARSdR-16 (with a mutated XDH gene) showed 70 and 40% of wild type (WT) XDH activity, respectively.
Conversions of xylose to xylitol by WT, XDH-5, and ARSdR-16 were 62, 64, and 75%, respectively, with productivities of 0.52,
0.54, and 0.62 g l−1 h−1, respectively. The ARSdR-16 mutant strain produced xylitol with high yield and high productivity in a simple process that
required no co-substrates, such as glycerol. This strain represents a promising alternative for efficient and cost-effective
xylitol production. 相似文献
4.
Muñoz AJ Hernández-Chávez G de Anda R Martínez A Bolívar F Gosset G 《Journal of industrial microbiology & biotechnology》2011,38(11):1845-1852
l-3,4-dihydroxyphenylalanine (l-DOPA) is an aromatic compound employed for the treatment of Parkinson's disease. Metabolic engineering was applied to generate
Escherichia coli strains for the production of l-DOPA from glucose by modifying the phosphoenolpyruvate:sugar phosphotransferase system (PTS) and aromatic biosynthetic pathways.
Carbon flow was directed to the biosynthesis of l-tyrosine (l-Tyr), an l-DOPA precursor, by transforming strains with compatible plasmids carrying genes encoding a feedback-inhibition resistant
version of 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase, transketolase, the chorismate mutase domain from chorismate mutase-prephenate dehydratase
from E. coli and cyclohexadienyl dehydrogenase from Zymomonas mobilis. The effects on l-Tyr production of PTS inactivation (PTS− gluc+ phenotype), as well as inactivation of the regulatory protein TyrR, were evaluated. PTS inactivation caused a threefold increase
in the specific rate of l-Tyr production (q
l-Tyr), whereas inactivation of TyrR caused 1.7- and 1.9-fold increases in q
l-Tyr in the PTS+ and the PTS− gluc+ strains, respectively. An 8.6-fold increase in l-Tyr yield from glucose was observed in the PTS− gluc+
tyrR
− strain. Expression of hpaBC genes encoding the enzyme 4-hydroxyphenylacetate 3-hydroxylase from E. coli W in the strains modified for l-Tyr production caused the synthesis of l-DOPA. One of such strains, having the PTS− gluc+
tyrR
− phenotype, displayed the best production parameters in minimal medium, with a specific rate of l-DOPA production of 13.6 mg/g/h, l-DOPA yield from glucose of 51.7 mg/g and a final l-DOPA titer of 320 mg/l. In a batch fermentor culture in rich medium this strain produced 1.51 g/l of l-DOPA in 50 h. 相似文献
5.
Hua Li Bao Shi Wang You Ran Li Liang Zhang Zhong Yang Ding Zheng Hua Gu Gui Yang Shi 《Journal of industrial microbiology & biotechnology》2017,44(1):75-88
In this study, we constructed an l-methionine-producing recombinant strain from wild-type Escherichia coli W3110 by metabolic engineering. To enhance the carbon flux to methionine and derepression met regulon, thrBC, lysA, and metJ were deleted in turn. Methionine biosynthesis obstacles were overcome by overexpression of metA Fbr (Fbr, Feedback resistance), metB, and malY under control of promoter pN25. Recombinant strain growth and methionine production were further improved by attenuation of metK gene expression through replacing native promoter by metK84p. Blocking the threonine pathway by deletion of thrBC or thrC was compared. Deletion of thrC showed faster growth rate and higher methionine production. Finally, metE, metF, and metH were overexpressed to enhance methylation efficiency. Compared with the original strain E. coli W3110, the finally obtained Me05 (pETMAFbr-B-Y/pKKmetH) improved methionine production from 0 to 0.65 and 5.62 g/L in a flask and a 15-L fermenter, respectively. 相似文献
6.
Summary. Hydrogensquarates of dipeptide l-threonyl-l-serine (H-Thr-Ser-OH) and l-serine (HSq × Ser) have been synthesized, isolated and spectroscopic characterized by solid-state linear-polarized IR-spectroscopy, 1H- and 13C-NMR, ESI-MS and HPLC with tandem masspectrometry (MS-MS) methods. The structures of the salts and neutral dipeptide have
been predicted theoretically by ab initio calculations. In the case of H-Thr-Ser-OH the theoretical data are supported by IR-LD ones. The hydrogensquarates consist in positive charged dipeptide or amino acid
moiety and negative hydrogensquarate anion (HSq) stabilizing by strong intermolecular hydrogen bonds. The data about the l-serine hydrogensquarate are compared with known crystallographic data thus indicating a good correlation between the theoretical
predicted structures and experimentally obtained by single crystal X-ray diffraction. 相似文献
7.
Kawaguchi H Sasaki M Vertès AA Inui M Yukawa H 《Applied microbiology and biotechnology》2008,77(5):1053-1062
Corynebacterium glutamicum was metabolically engineered to broaden its substrate utilization range to include the pentose sugar l-arabinose, a product of the degradation of lignocellulosic biomass. The resultant CRA1 recombinant strain expressed the Escherichia coli genes araA, araB, and araD encoding l-arabinose isomerase, l-ribulokinase, and l-ribulose-5-phosphate 4-epimerase, respectively, under the control of a constitutive promoter. Unlike the wild-type strain,
CRA1 was able to grow on mineral salts medium containing l-arabinose as the sole carbon and energy source. The three cloned genes were expressed to the same levels whether cells were
cultured in the presence of d-glucose or l-arabinose. Under oxygen deprivation and with l-arabinose as the sole carbon and energy source, strain CRA1 carbon flow was redirected to produce up to 40, 37, and 11%,
respectively, of the theoretical yields of succinic, lactic, and acetic acids. Using a sugar mixture containing 5% d-glucose and 1% l-arabinose under oxygen deprivation, CRA1 cells metabolized l-arabinose at a constant rate, resulting in combined organic acids yield based on the amount of sugar mixture consumed after
d-glucose depletion (83%) that was comparable to that before d-glucose depletion (89%). Strain CRA1 is, therefore, able to utilize l-arabinose as a substrate for organic acid production even in the presence of d-glucose. 相似文献
8.
Yukio Yoneda 《Neurochemical research》2017,42(10):2686-2697
l-Theanine (=γ-glutamylethylamide) is an amino acid ingredient in green tea with a structural analogy to l-glutamine (l-GLN) rather than l-glutamic acid (l-GLU), with regards to the absence of a free carboxylic acid moiety from the gamma carbon position. l-theanine markedly inhibits [3H]l-GLN uptake without affecting [3H]l-GLU uptake in cultured neurons and astroglia. In neural progenitor cells with sustained exposure to l-theanine, upregulation of the l-GLN transporter isoform Slc38a1 expression and promotion of both proliferation and neuronal commitment are seen along with marked acceleration of the phosphorylation of mammalian target of rapamycin (mTOR) and relevant downstream proteins. Stable overexpression of Slc38a1 leads to promotion of cellular growth with facilitated neuronal commitment in pluripotent embryonic carcinoma P19 cells. In P19 cells stably overexpressing Slc38a1, marked phosphorylation is seen with mTOR and downstream proteins in a fashion insensitive to the additional stimulation by l-theanine. The green tea amino acid l-theanine could thus elicit pharmacological actions to up-regulate Slc38a1 expression for activation of the mTOR signaling pathway required for cell growth together with accelerated neurogenesis after sustained exposure in undifferentiated neural progenitor cells. In this review, I summarize a novel pharmacological property of the green tea amino acid l-theanine for embryonic and adult neurogenesis with a focus on the endogenous amino acid analog l-GLN. A possible translational strategy is also discussed on the development of dietary supplements and nutraceuticals enriched of l-theanine for the prophylaxis of a variety of untoward impairments and malfunctions seen in patients with different neurodegenerative and/or neuropsychiatric disorders. 相似文献
9.
Jiwei Mao Quanli Liu Xiaofei Song Hesuiyuan Wang Hui Feng Haijin Xu Mingqiang Qiao 《Biotechnology letters》2017,39(7):977-982
Objective
To identify new enzymatic bottlenecks of l-tyrosine pathway for further improving the production of l-tyrosine and its derivatives.Result
When ARO4 and ARO7 were deregulated by their feedback resistant derivatives in the host strains, the ARO2 and TYR1 genes, coding for chorismate synthase and prephenate dehydrogenase were further identified as new important rate-limiting steps. The yield of p-coumaric acid in the feedback-resistant strain overexpressing ARO2 or TYR1, was significantly increased from 6.4 to 16.2 and 15.3 mg l?1, respectively. Subsequently, we improved the strain by combinatorial engineering of pathway genes increasing the yield of p-coumaric acid by 12.5-fold (from 1.7 to 21.3 mg l?1) compared with the wild-type strain. Batch cultivations revealed that p-coumaric acid production was correlated with cell growth, and the formation of by-product acetate of the best producer NK-M6 increased to 31.1 mM whereas only 19.1 mM acetate was accumulated by the wild-type strain.Conclusion
Combinatorial metabolic engineering provides a new strategy for further improvement of l-tyrosine or other metabolic biosynthesis pathways in S. cerevisiae.10.
Deutch CE 《Antonie van Leeuwenhoek》2011,99(4):781-793
Staphylococcus saprophyticus strains ATCC 15305, ATCC 35552, and ATCC 49907 were found to require l-proline but not l-arginine for growth in a defined culture medium. All three strains could utilize l-ornithine as a proline source and contained l-ornithine aminotransferase and Δ1-pyrroline-5-carboxylate reductase activities; strains ATCC 35552 and ATCC 49907 could use l-arginine as a proline source and had l-arginase activity. The proline requirement also could be met by l-prolinamide, l-proline methyl ester, and the dipeptides l-alanyl-l-proline and l-leucyl-l-proline. The bacteria exhibited l-proline degradative activity as measured by the formation of Δ1-pyrroline-5-carboxylate. The specific activity of proline degradation was not affected by addition of l-proline or NaCl but was highest in strain ATCC 49907 after growth in Mueller–Hinton broth. A membrane fraction from this
strain had l-proline dehydrogenase activity as detected both by reaction of Δ1-pyrroline-5-carboxylate with 2-aminobenzaldehyde (0.79 nmol min−1 mg−1) and by the proline-dependent reduction of p-iodonitrotetrazolium (20.1 nmol min−1 mg−1). A soluble fraction from this strain had Δ1-pyrroline-5-carboxylate dehydrogenase activity (88.8 nmol min−1 mg−1) as determined by the NAD+-dependent oxidation of dl-Δ1-pyrroline-5-carboxylate. Addition of l-proline to several culture media did not increase the growth rate or final yield of bacteria but did stimulate growth during
osmotic stress. When grown with l-ornithine as the proline source, S. saprophyticus was most susceptible to the proline analogues L-azetidine-2-carboylate, 3,4-dehydro-dl-proline, dl-thiazolidine-2-carboxylate, and l-thiazolidine-4-carboxylate. These results indicate that proline uptake and metabolism may be a potential target of antimicrobial
therapy for this organism. 相似文献
11.
Li Y Kawakami N Ogola HJ Ashida H Ishikawa T Shibata H Sawa Y 《Applied microbiology and biotechnology》2011,90(6):1953-1962
l-aspartate dehydrogenase (EC 1.4.1.21; l-AspDH) is a rare member of amino acid dehydrogenase superfamily and so far, two thermophilic enzymes have been reported.
In our study, an ORF PA3505 encoding for a putative l-AspDH in the mesophilic bacterium Pseudomonas aeruginosa PAO1 was identified, cloned, and overexpressed in Escherichia coli. The homogeneously purified enzyme (PaeAspDH) was a dimeric protein with a molecular mass of about 28 kDa exhibiting a very
high specific activity for l-aspartate (l-Asp) and oxaloacetate (OAA) of 127 and 147 U mg−1, respectively. The enzyme was capable of utilizing both nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine
dinucleotide phosphate (NADP) as coenzyme. PaeAspDH showed a T
m value of 48°C for 20 min that was improved to approximately 60°C by the addition of 0.4 M NaCl or 30% glycerol. The apparent
K
m values for OAA, NADH, and ammonia were 2.12, 0.045, and 10.1 mM, respectively; comparable results were observed with NADPH.
The l-Asp production system B consisting of PaeAspDH, Bacillus subtilis malate dehydrogenase and E. coli fumarase, achieved a high level of l-Asp production (625 mM) from fumarate in fed-batch process with a molar conversion yield of 89.4%. Furthermore, the fermentative
production system C released 33 mM of l-Asp after 50 h by using succinate as carbon source. This study represented an extensive characterization of the mesophilic
AspDH and its potential applicability for efficient and attractive production of l-Asp. Our novel production systems are also hopeful for developing the new processes for other compounds production. 相似文献
12.
Hailong Chen Zhilai Wang Haibo Cai Changlin Zhou 《World journal of microbiology & biotechnology》2016,32(9):153
S-Adenosyl-l-methionine (SAM), which exists in all living organisms, serves as an activated group donor in a range of metabolic reactions, including trans-methylation, trans-sulfuration and trans-propylamine. Compared with its chemical synthesis and enzyme catalysis production, the microbial production of SAM is feasible for industrial applications. The current clinical demand for SAM is constantly increasing. Therefore, vast interest exists in engineering the SAM metabolism in cells for increasing product titers. Here, we provided an overview of updates on SAM microbial productivity improvements with an emphasis on various strategies that have been used to enhance SAM production based on increasing the precursor and co-factor availabilities in microbes. These strategies included the sections of SAM-producing microbes and their mutant screening, optimization of the fermentation process, and the metabolic engineering. The SAM-producing strains that were used extensively were Saccharomyces cerevisiae, Pichia pastoris, Candida utilis, Scheffersomyces stipitis, Kluyveromyces lactis, Kluyveromyces marxianus, Corynebacterium glutamicum, and Escherichia coli, in addition to others. The optimization of the fermentation process mainly focused on the enhancement of the methionine, ATP, and other co-factor levels through pulsed feeding as well as the optimization of nitrogen and carbon sources. Various metabolic engineering strategies using precise control of gene expression in engineered strains were also highlighted in the present review. In addition, some prospects on SAM microbial production were discussed. 相似文献
13.
Yoshinori Takagi Teruhide Sugisawa Tatsuo Hoshino 《Applied microbiology and biotechnology》2009,82(6):1049-1056
A single-stage continuous fermentation process for the production of 2-keto-l-gulonic acid (2KGA) from l-sorbose using Ketogulonigenium vulgare DSM 4025 was developed. The chemostat culture with the dilution rate that was calculated based on the relationship between
the 2KGA production rate and the 2KGA concentration was feasible for production with high concentration of 2KGA. In this system,
112.2 g/L of 2KGA on the average was continuously produced from 114 g/L of l-sorbose. A steady state of the fermentation was maintained for the duration of more than 110 h. The dilution rate was kept
in the range of 0.035 and 0.043 h−1, and the 2KGA productivity was 3.90 to 4.80 g/L/h. The average molar conversion yield of 2KGA from l-sorbose was 91.3%. Under the optimal conditions, l-sorbose concentration was kept at 0 g/L. Meanwhile, the dissolved oxygen level was changing in response to the dilution rate
and 2KGA concentration. In the dissolved oxygen (DO) range of 16% to 58%, it was revealed that the relationship between DO
and D possessed high degree of positive correlation under the l-sorbose limiting condition (complete consumption of l-sorbose). Increasing D closer to the critical value for washing out point of the continuous fermentation, DO value tended to be gradually increased
up to 58%. In conclusion, an efficient and reproducible continuous fermentation process for 2KGA production by K. vulgare DSM 4025 could be developed using a medium containing baker’s yeast without using a second helper microorganism. 相似文献
14.
Xiong H Turunen O Pastinen O Leisola M von Weymarn N 《Applied microbiology and biotechnology》2004,64(3):353-358
Trichoderma reesei Rut C-30 was grown on eight different natural or rare aldopentoses as the main carbon source and on mixtures of an aldopentose with d-glucose or lactose. The fungal cells consumed all aldopentoses tested, except l-xylose and l-ribose. The highest total xylanase and cellulase activities were achieved when cells were grown on l-arabinose as the main carbon source. The total xylanase activity produced by cells grown on l-arabinose was even higher than that produced by cells grown on an equal amount of lactose. In co-metabolism of d-glucose (15 g l–1) and l-arabinose (5 g l–1), the total volumetric and specific xylanase productivities were improved (derepressed) approximately 23- and 18-fold, respectively, compared to a cultivation on only d-glucose (20 g l–1). In a similar experiment, in which cells were grown on a mixture of lactose and l-arabinose, the xylanase productivity was approximately doubled, compared to a cultivation on only lactose. The cellulase productivities, however, were not improved by the addition of l-arabinose. Compared with a typical industrial fungal enzyme production process with lactose as the main carbon source, better volumetric and specific xylanase productivities were achieved both on a lactose/arabinose mixture and on a glucose/arabinose mixture. 相似文献
15.
d-Tagatose is a highly functional rare ketohexose and many attempts have been made to convert d-galactose into the valuable d-tagatose using l-arabinose isomerase (l-AI). In this study, a thermophilic strain possessing l-AI gene was isolated from hot spring sludge and identified as Anoxybacillus flavithermus based on its physio-biochemical characterization and phylogenetic analysis of its 16s rRNA gene. Furthermore, the gene encoding
l-AI from A. flavithermus (AFAI) was cloned and expressed at a high level in E. coli BL21(DE3). l-AI had a molecular weight of 55,876 Da, an optimum pH of 10.5 and temperature of 95°C. The results showed that the conversion
equilibrium shifted to more d-tagatose from d-galactose by raising the reaction temperatures and adding borate. A 60% conversion of d-galactose to d-tagatose was observed at an isomerization temperature of 95°C with borate. The catalytic efficiency (k
cat
/K
m) for d-galactose with borate was 9.47 mM−1 min−1, twice as much as that without borate. Our results indicate that AFAI is a novel hyperthermophilic and alkaliphilic isomerase
with a higher catalytic efficiency for d-galactose, suggesting its great potential for producing d-tagatose. 相似文献
16.
Ratna Mohd Tap Teck Choon Lim Nur Amalina Kamarudin Stephanie Jane Ginsapu Mohd Fuat Abd Razak Norazah Ahmad Fairuz Amran 《Mycopathologia》2018,183(3):559-564
We report a fatal case of Candida auris that was involved in mixed candidemia with Candida tropicalis, isolated from the blood of a neutropenic patient. Identification of both isolates was confirmed by amplification and sequencing of internal transcribed spacer and D1/D2 domain of large subunit in rRNA gene. Antifungal susceptibility test by E-test method revealed that C. auris was resistant to amphotericin B, anidulafungin, caspofungin, fluconazole, itraconazole and voriconazole. On the other hand, C. tropicalis was sensitive to all antifungal tested. The use of chromogenic agar as isolation media is vital in detecting mixed candidemia. 相似文献
17.
l-arabinose isomerase (EC5.3.1.4. AI) mediates the isomerization of d-galactose into d-tagatose as well as the conversion of l-arabinose into l-ribulose. The AI from Lactobacillus plantarum SK-2 was purified to an apparent homogeneity giving a single band on SDS–PAGE with a molecular mass of 59.6 kDa. Optimum
activity was observed at 50°C and pH 7.0. The enzyme was stable at 50°C for 2 h and held between pH 4.5 and 8.5 for 1 h. AI
activity was stimulated by Mn2+, Fe3+, Fe2+, Ca2+ and inhibited by Cu2+, Ag+, Hg2+, Pb2+. d-galactose and l-arabinose as substrates were isomerized with high activity. l-arabitol was the strongest competitive inhibitor of AI. The apparent Michaelis–Menten constant (K
m), for galactose, was 119 mM. The first ten N-terminal amino acids of the enzyme were determined as MLSVPDYEFW, which is identical to L. plantarum (Q88S84). Using the purified AI, 390 mg tagatose could be converted from 1,000 mg galactose in 96 h, and this production
corresponds to a 39% equilibrium. 相似文献
18.
Mark S. Ou Lonnie O. Ingram K. T. Shanmugam 《Journal of industrial microbiology & biotechnology》2011,38(5):599-605
Lactic acid is used as an additive in foods, pharmaceuticals, and cosmetics, and is also an industrial chemical. Optically
pure lactic acid is increasingly used as a renewable bio-based product to replace petroleum-based plastics. However, current
production of lactic acid depends on carbohydrate feedstocks that have alternate uses as foods. The use of non-food feedstocks
by current commercial biocatalysts is limited by inefficient pathways for pentose utilization. B. coagulans strain 36D1 is a thermotolerant bacterium that can grow and efficiently ferment pentoses using the pentose-phosphate pathway
and all other sugar constituents of lignocellulosic biomass at 50°C and pH 5.0, conditions that also favor simultaneous enzymatic
saccharification and fermentation (SSF) of cellulose. Using this bacterial biocatalyst, high levels (150–180 g l−1) of lactic acid were produced from xylose and glucose with minimal by-products in mineral salts medium. In a fed-batch SSF
of crystalline cellulose with fungal enzymes and B. coagulans, lactic acid titer was 80 g l−1 and the yield was close to 80%. These results demonstrate that B. coagulans can effectively ferment non-food carbohydrates from lignocellulose to l(+)-lactic acid at sufficient concentrations for commercial application. The high temperature fermentation of pentoses and
hexoses to lactic acid by B. coagulans has these additional advantages: reduction in cellulase loading in SSF of cellulose with a decrease in enzyme cost in the
process and a reduction in contamination of large-scale fermentations. 相似文献
19.
Zhu L Tao R Wang Y Jiang Y Lin X Yang Y Zheng H Jiang W Yang S 《Applied microbiology and biotechnology》2011,90(3):903-910
l-2-Aminobutyric acid can be synthesized in a transamination reaction from l-threonine and l-aspartic acid as substrates by the action of threonine deaminase and aromatic aminotransferase, but the by-product l-alanine was produced simultaneously. A small amount of l-alanine increased the complexity of the l-2-aminobutyric acid recovery process because of their extreme similarity in physical and chemical properties. Acetolactate
synthase has been introduced to remove the pyruvate intermediate for reducing the l-alanine concentration partially. To eliminate the remnant l-alanine, alanine racemase of Bacillus subtilis in combination with d-amino acid oxidase of Rhodotorula gracilis or Trigonopsis variabilis respectively was introduced into the reaction system for the l-2-aminobutyric acid synthesis. l-Alanine could be completely removed by the action of alanine racemase of B. subtilis and d-amino acid oxidase of R. gracilis; thereby, high-purity l-2-aminobutyric acid was achieved. The results revealed that alanine racemase could discriminate effectively between l-alanine and l-2-aminobutyric acid, and selectively catalyzed l-alanine to d-alanine reversibly. d-Amino acid oxidase then catalyzed d-alanine to pyruvate stereoselectively. Furthermore, this method was also successfully used to remove the by-product l-alanine in the production of other neutral amino acids such as l-tertiary leucine and l-valine, suggesting that multienzymatic whole-cell catalysis can be employed to provide high purity products. 相似文献
20.
Xiuling Shang Xin Chai Xuemei Lu Yuan Li Yun Zhang Guoqiang Wang Chen Zhang Shuwen Liu Yu Zhang Jiyin Ma Tingyi Wen 《Biotechnology letters》2018,40(2):383-391