（S）-（-）-β-羟基苯丙酸乙酯的微生物法合成

采用酿酒酵母CGMCC No．2266菌体,不对称还原β-羰基苯丙酸乙酯制备光学纯（S）-（-）-β-羟基苯丙酸乙酯。结果表明：采用初始pH为8．0的液体发酵培养基培养的CGMCCNo．2266菌体经过50℃预热处理30min后用于生物转化获得的（S）-（-）-G-羟基苯丙酸乙酯对映体过剩值可以达到100％ee。确定了合成（S）-（-）-β-羟基苯丙酸乙酯的较佳转化条件为pH7．0,温度30℃,转化时间24h,底物浓度为3．63mmol／L,菌体用量为86g/L（干重／反应体积）。以10％葡萄糖为辅助底物,产率比不加辅助底物时提高了75．4％。在最佳转化条件下反应转化率及（S）-（-）-β-羟基苯丙酸乙酯对映体过剩值可分别达到98．4％和100％ee。     

Preparation of 2S-(—)-4-Amino-2-Hydroxybutanoic Acid via Yeast-Catalyzed Stereoselective Reduction

The unusual amino acid S2-(—)-4-amino-2-hydroxybutanoic acid (S-AHBA) (1), a structural component of the antibiotic Amikacin, has been prepared via yeast-catalyzed stereoselective reduction of methyl-4-benzyloxycarbonyloxyamino-2-oxobutanoate (5). The most suitable yeast was found to be Saccharomyces carlsbergensis ATCC2345 and Saccharomyces sp. Edme, which gave 40% and 54% yield, respectively, of (S)-(+)-6 (88% ee).     

代谢工程改造酿酒酵母生产L-乳酸的研究进展

L-乳酸是一种重要的有机化合物,具有广泛的应用价值。微生物发酵法生产是当前L-乳酸的主要来源,但受限于精确的发酵条件、菌体产物耐受能力低及底物要求高等因素,导致L-乳酸供给不足且价格偏高。鉴于酿酒酵母利用廉价底物生产有价值物质方面的诸多优势,并随着分子生物学技术的发展,利用代谢工程改造酿酒酵母本身固有的代谢网络,使其高产L-乳酸已成为当前研究的热点。从L-乳酸的异源生产、关键途径改造及菌体生长能力恢复三个方面归纳了关于代谢工程改造酿酒酵母生产L-乳酸的研究进展。最后,指出了酿酒酵母异源生产L-乳酸存在的不足和今后研究的方向。     

Synthesis of a Glandular Secretion of the Civet Cat, (2S,6S)-(6-Methyltetrahydropyran-2-yl)acetic Acid and Its Enantiomer,by Using the Yeast-Reduction Product and Recovered Substrate from Yeast Reduction

A glandular secretion of the civet cat, (2S,6S)-(6-methyltetrahydropyran-2-yl)acetic acid 1 and its enantiomer, were synthesized from the yeast-reduction product and recovered substrate from yeast reduction.     

Enantioselective microbial reduction of 3,5-dioxo-6-(benzyloxy) hexanoic acid, ethyl ester

The key chiral intermediate 3,5-dihydroxy-6-(benzyloxy) hexanoic acid, ethyl ester 2a, was made by the stereoselective microbial reduction of 3,5-dioxo-6-(benzyloxy) hexanoic acid, ethyl ester 1. Among various microbial cultures evaluated, cell suspensions of Acinetobacter calcoaceticus SC 13876 reduced 1 to 2a. The reaction yield of 85% and optical purity of 97% was obtained using glycerol-grown cells. The substrate was used at 2 g l⁻¹ and cells were used at 20% (w/v, wet cells) concentrations. The optimum pH for the reduction of 1 to 2a was 5.5 and the optimum temperature was 32°C. Cell extracts of A. calcoaceticus SC 13876 in the presence of NAD⁺, glucose, and glucose dehydrogenase reduced 1 to the corresponding monohydroxy compounds 3 and 4 [3-hydroxy-5-oxo-6-(benzyloxy) hexanoic acid ethyl ester 3, and 5-hydroxy-3-oxo-6-(benzyloxy) hexanoic acid ethyl ester 4]. Both 3 and 4 were further reduced to 2a by cell extracts. Reaction yield of 92% and optical purity of 99% were obtained when the reaction was carried out in a 1-l batch using cell extracts. The substrate was used at 10 g l⁻¹. Product 2a was isolated from the reaction mixture in 72% overall yield. The GC and HPLC area % purity of the isolated product was 99% and the optical purity was 99.5%. The reductase which converted 1 to 2a was purified about 200-fold from cell extracts of A. calcoaceticus SC 13876. The purified enzyme gave a single protein band on SDS-PAGE corresponding to 35,000 daltons.     

水/有机溶剂双相中固定化啤酒酵母细胞催化有机硅酮不对称还原

研究了水/有机溶剂双相中,固定化啤酒酵母细胞催化三甲基硅乙酮不对称还原成（－）-1-三甲基硅乙醇的反应,系统探讨了振荡速度、有机溶剂疏水性、水相与有机溶剂相体积比、水相pH值和反应温度对反应速度、产率和产物光学纯度的影响.结果表明,上述因素对固定化啤酒酵母细胞催化三甲基硅乙酮不对称还原反应均有较显著的影响.正己烷为该反应最好的有机溶剂,振荡速度以150 r/min为宜,水相与有机溶剂相体积比以1∶2较佳,适宜的pH值为8,最佳反应温度为25～30℃.在该优化反应条件下,反应最大产率和产物的光学纯度分别高达96.8％和95.7％(ee).     

酿酒酵母by1.1b产D-(-)-扁桃酸脱氢酶的发酵条件优化

对一株产D-(-)-扁桃酸对映选择性脱氢酶的酿酒酵母菌(Saccharomyces cerevisiae sp.strain by1.1b)发酵产酶条件进行了优化.研究各种碳源、氮源及无机盐对产酶的影响,应用正交试验优化发酵培养基组成,结果为:蛋白胨60 g/L,麦芽糖30 g/L,MgSO4 0.5 g/L,ZnSO4 0.01 g/L,KCl 1.0 g/L.优化后酶产量提高了7.9倍(由2.56 U/mL增至20.21 U/mL).摇瓶培养最佳条件为:装液量40%,发酵pH 6.5,接种量10%,发酵温度30℃.考察了细胞生长及产酶的时间进程,最佳培养时间为25 h.     

Requirements for Nutrients and Minerals by Candida brumptii IFO 0731 Producing Succinic Acid from n-Paraffin

The effect of several materials on viscometric behaviour of the soluble ovomucin was determined with a cone plate viscometer.

The soluble ovomucin showed a rapid increase in viscosity above 1.5 mg/ml, and a high concentration of the soluble ovomucin led to gel whose viscosity was comparable to that of the insoluble ovomucin. The apparent viscosity of the soluble ovomucin decreased with an increase in NaCl concentration and upon addition of lysozyme as well as of CaCl₂. The soluble ovomucin in the presence of the sonicated β-ovomucin showed an increase in viscosity on addition of a small amount of CaCl₂.

It is assumed that a great increase in viscosity of egg white may result from removal of sodium ion and lysozyme.     

酿酒酵母by1.1b产D-(-)-扁桃酸脱氢酶的发酵条件优化

对一株产D-(-)-扁桃酸对映选择性脱氢酶的酿酒酵母菌(Saccharomyces cerevisiae sp. strain by1.1b)发酵产酶条件进行了优化。研究各种碳源、氮源及无机盐对产酶的影响, 应用正交试验优化发酵培养基组成, 结果为: 蛋白胨 60 g/L, 麦芽糖 30 g/L, MgSO4 0.5 g/L, ZnSO4 0.01 g/L, KCl 1.0 g/L。优化后酶产量提高了7.9倍(由2.56 U/mL增至20.21 U/mL)。摇瓶培养最佳条件为: 装液量40 %, 发酵pH 6.5, 接种量10 %, 发酵温度30 ℃。考察了细胞生长及产酶的时间进程, 最佳培养时间为25 h。     

Nitrogen catabolite repression modulates the production of aromatic thiols characteristic of Sauvignon Blanc at the level of precursor transport

The free thiols 3-mercapto-hexanol (3MH) and its acetate, practically absent from musts, are liberated by yeast during fermentation from a cysteinylated precursor [S-3-(hexan-1-ol)-l-cysteine (Cys-3MH)] present in the grape must and contribute favorably to the flavor of Sauvignon white wines. Production of 3MH is increased when urea is substituted for diammonium phosphate (DAP) as the sole nitrogen source on a synthetic medium. On grape must, complementation with DAP induces a decrease of 3MH production. This observation is reminiscent of nitrogen catabolite repression (NCR). The production of 3MH is significantly lower for a gap1Delta mutant compared with the wild type, during fermentation of a synthetic medium containing Cys-3MH as the precursor and urea as the sole nitrogen source. Mutants isolated from an enological strain with a relief of NCR on GAP1 produce significantly higher amounts of 3MH on synthetic medium than the parental strain. These phenotypes were not confirmed on grape must. It is concluded that on synthetic medium, Cys-3MH enters the cell through at least one identified transporter, GAP1p, whose activity is limiting the release of volatile thiols. On grape must, the uptake of the precursor through GAP1p is not confirmed, but the effect of addition of DAP, eventually prolonging NCR, is shown to decrease thiol production.     

Biotransformation of a crizotinib intermediate using a mutant alcohol dehydrogenase of Lactobacillus kefir coupled with glucose dehydrogenase

Abstract

(S)-1-(2, 6-dichloro-3-fluorophenyl) ethanol, the key chiral intermediate of crizotinib, was prepared from 1-(2, 6-dichloro-3-fluorophenyl) ethanone using the alcohol dehydrogenases from Lactobacillus kefir (ADH-LK) with a tetrad mutant (ADH-LKM, F147L/Y190P/V196L/A202W), coupled with glucose dehydrogenase (GDH). In the present study, ADH-LKM and GDH were successfully heterologous expressed in recombinant Escherichia coli. During the regeneration of NADPH with GDH, 150?g/L substrate was totally transformed into target chiral alcohol with an enantiomeric excess value of 99.9% after 12?h at 30?°C (pH 7.0). Our study demonstrates the potential for industrial green production of the key chiral intermediate of crizotinib.     

Improvement of natural isolates of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> strains for synthesis of a chiral building block using classic genetics

The asymmetric bio-reduction of 4-chloro-acetoacetic-acid-ethyl-ester to the pharmaceutical building block (S)-4-chloro-3-hydroxybutanoate-ethyl-ester requires the utilization of an enantioselective robust biocatalyst. Some of the natural Saccharomyces cerevisiae strains, isolated from Mount Carmel National Park in Israel, were characterized as resistant to environmental stress. Nevertheless, these strains showed relatively low enantiomeric-excess (ee), while a laboratory strain, Y103, exhibited a selectivity of 98% ee. The enantioselective lab strain was crossed with the multi-stress resistant environmental isolate (93% ee) followed by backcross with Y103, to subsequently obtain a haploid offspring of backcross-1, exhibiting both high multi-stress resistance and high enantioselectivity (98% ee). Introducing osmotic (1 M NaCl), oxidative (0.6 mM H₂O₂) and thermal stress (44°C) to growing cultures of the enantioselective parent, resulted in a decrease of 24–32% in specific activity, while the enantioselectivity of the stress-resistant parent decreased by 4–12% ee. Unlike its original parental strains, the new strain maintained constant specific activity and enantioselectivity when introduced to the various stress factors. This work shows that the classic introgression method, can serve as a viable approach for creating a robust enantioselective biocatalyst, designed for industrial production of chiral compounds.     

(3R)-2-羧乙基-3-氰基-5-甲基己酸乙酯水解酶产生菌的筛选与产酶条件优化

以2-羧乙基-3-氰基-5-甲基己酸乙酯为唯一碳源,采用手性气相法检测,筛选到一株能产对映选择性水解酶的假单胞菌Pseudomonas CGMCC No.4184.该菌产的水解酶能优先水解R型底物产生(3R)-2-羧乙基-3-氰基-5-甲基己酸,产物对映体过量值达到90%以上.对菌株Pseudomonas CGMCC ...     

莽草酸芳构化制备二芳基胺类化合物

以莽草酸为起始物,经酯化及IBX氧化制备得到3-脱氢莽草酸甲酯。在甲醇溶剂中及对甲苯磺酸的催化下,3-脱氢莽草酸甲酯与芳香伯胺类化合物发生缩合-脱水芳构化反应,制备得到一类二芳基胺类化合物,即3-芳胺基-4-羟基苯甲酸甲酯类化合物。该方法以廉价的可再生资源为起始物,具有操作简单、条件温和、收率高等优点,是制备二芳基胺类化合物的一种有效途径。     

(S)-3-Pentyn-2-ol production through microbial enzyme-catalyzed, highly enantioselective hydrolysis of racemic 3-pentyn-2-ol esters

Air-dried cells of Hansenula nonfermentans AKU 4332 catalyzed the production of (S)-3-pentyn-2-ol from (RS)-3- pentyn-2-ol acetate ester at 10% (v/v). The product was formed at 96.6% e.e. with a molar yield of 45% in 24 h. © Rapid Science Ltd. 1998     

Downscaling screening cultures in a multifunctional bioreactor array-on-a-chip for speeding up optimization of yeast-based lactic acid bioproduction

A key challenge for bioprocess engineering is the identification of the optimum process conditions for the production of biochemical and biopharmaceutical compounds using prokaryotic as well as eukaryotic cell factories. Shake flasks and bench-scale bioreactor systems are still the golden standard in the early stage of bioprocess development, though they are known to be expensive, time-consuming, and labor-intensive as well as lacking the throughput for efficient production optimizations. To bridge the technological gap between bioprocess optimization and upscaling, we have developed a microfluidic bioreactor array to reduce time and costs, and to increase throughput compared with traditional lab-scale culture strategies. We present a multifunctional microfluidic device containing 12 individual bioreactors (V_t = 15 µl) in a 26 mm × 76 mm area with in-line biosensing of dissolved oxygen and biomass concentration. Following initial device characterization, the bioreactor lab-on-a-chip was used in a proof-of-principle study to identify the most productive cell line for lactic acid production out of two engineered yeast strains, evaluating whether it could reduce the time needed for collecting meaningful data compared with shake flasks cultures. Results of the study showed significant difference in the strains' productivity within 3 hr of operation exhibiting a 4- to 6-fold higher lactic acid production, thus pointing at the potential of microfluidic technology as effective screening tool for fast and parallelizable industrial bioprocess development.     

Enantiospecific enzymatic preparation of (2S,3S)-3-alkylaspartic acids of current interest in the synthesis of stereoregular poly[β-(2S,3S)-3-alkylmalic acids] as new optically active functional polyesters

(2S,3S)-3-methyl- and 3-isopropylaspartic acids were synthesized by bioconversion of the corresponding alkylfumarates (mesaconate and 3-isopropylfumarate) using β-methylaspartase from cell-free extracts of Clostridium tetanomorphum. Optically pure (2S,3S)-3-alkylaspartic acids were transformed in several steps to benzyl (3S,4R)-3-alkylmalolactonates without any racemization of the two chiral centers. These optically active α,β-substituted-β-lactones were polymerized by anionic ring opening polymerization yielding optically active semi-crystalline polyesters. ¹³C NMR analysis of poly[benzyl β-3-isopropylmalate] in CDCl₃ has shown that only the iso-type stereosequence is present in the polymer, indicating that the macromolecular chain is constituted by the only units of benzyl β-(2S,3S)-3-isopropylmalate monomer. The polymerization reaction was done without any racemization of the two stereogenic centers as in the case of benzyl (3S,4R)-3-methylmalolactonate. © 1996 Wiley-Liss, Inc.     

Effects of Polyols and Sugars on the Sol-Gel Transition of Gelatin

The melting temperature of gelatin gel increased with increasing concentrations of polyols and sugars added at any gelatin concentation. The enthalpy of gel melting measured by Eldridge-Ferry plots and calorimetric measurements was decreased by addition of these polyhydric compounds, indicating that the gel stabilization by them is predominantly due to the large decrease in entropy of gel melting. Circular dichroism analysis showed that the helix formation of gelatin molecules was enhanced with increasing concentrations of these additives, but there was no positive correlation between their helix-forming ability and gel-stabilizing ability. The viscosity of gelatin solution was less in these mixed solvents than in water. Based on these results, a possible stabilization mechanism of gelatin gel by polyhydric compounds was discussed, in comparison with that of native collagen, in terms of the thermodynamics of protein-solvent interactions.     

高选择性不对称还原N,N-二甲基-3-酮-3-(2-噻吩)-1-丙胺的重组氧化还原酶催化性质及其酶促转化

【目的】通过表达多种重组立体选择性氧化还原酶,分析其催化不对称还原N,N-二甲基-3-酮-3-(2-噻吩)-1-丙胺(DKTP)的性质,从而构建酶促合成(S)-N,N-二甲基-3-羟基-3-(2-噻吩)-1-丙胺(DHTP)的反应体系。【方法】基于已有立体选择性氧化还原酶重组大肠杆菌,通过Ni离子亲和层析法纯化得到重组氧化还原酶,以DKTP为底物,考察不同重组氧化还原酶对DKTP的催化活性和选择性,进一步对高选择性酶促合成(S)-DHTP的重组酶CR2进行性质分析,并考察其在最适条件下不对称还原DKTP的过程。【结果】筛选获得产物构型为(S)-型的催化活性最高的酶为CR2,该酶米氏常数Km为0.135 mmol/L,kcat/Km为3.689 L/(mmol·s),最适p H 8.4(0.1 mol/L三乙醇胺缓冲液),最适反应温度为35°C,在10-45°C条件下和p H 7.5-8.5较为稳定,Zn2+离子对酶活有促进作用。CR2催化DKTP不对称还原反应6 h后,DHTP的产率达92.1%、光学纯度达99.9%。【结论】基于活性和选择性分析,获得不对称还原DKTP的目标酶CR2,其催化特性有利于高立体选择性还原DKTP生成度洛西汀中间体(S)-DHTP,从而为进一步提高酶促不对称还原DKTP的转化效率提供研究基础。