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几种添加物对D—核糖产量的影响 总被引:1,自引:0,他引:1
研究了几种物质对D-核糖产量的影响,研究表明,当发酵培养基中玉米浆的含量为25g/L,D-核糖产量达到最高,为65g/L。发酵培养基中添加适量的粉及山梨醇亦有利于D-核糖的积累,当粉与山梨醇的添加量分别为10g/L及40g/L时,D-核糖产率分别增加7.8%、4.7%,而在发酵培养基中加入丙二酸可抑制D-核的分泌,在40ml发酵培养基中添加1ml丙二酸后,D-核糖的产率下降73.8%。甲醇也可抑制D-核糖的积累,当发酵培养基中的甲醇添加量为16g/L时,D-核糖产率下降66.2%。 相似文献
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目的:研究球头三型孢菌Trichosporonoides oedocephalis ATCC 16958发酵生产核糖醇的工艺.方法:采用摇瓶发酵优化的方式,探索培养基组份及三羧酸循环抑制剂对该菌生长及发酵生产核糖醇的影响,并在7L发酵罐中对优化的条件进行发酵验证.结果:对于核糖醇生产,葡萄糖和酵母膏分别是最佳的碳源和氮源,当葡萄糖浓度为20%时,核糖醇产量为38.60g/L.以1%酵母膏为氮源时,核糖醇浓度为37.82g/L.发酵24h添加0.2%的柠檬酸,核糖醇产量提高30.35%.采用摇瓶培养的优化条件,在7L发酵罐中发酵120h核糖醇产量为38.66g/L.结论:实验获得的优化条件可进一步用于指导生产. 相似文献
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D-核糖发酵过程参数的研究与控制 总被引:5,自引:0,他引:5
以7L自控发酵罐进行D-核糖发酵实验,对D-核糖发酵过程参数进行优化,发现对数生长后期接种,溶氧控制在40%左右,以葡萄糖酸补料并调节pH值在7.2左右,可使罐的发酵单位由45g/L提高至65g/L左右。 相似文献
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使用转酮醇酶变异株-枯草芽孢杆菌C1-B941进行了D-核糖发酵中间试验。3000L发酵罐试验结果表明,发酵培养基中的葡萄糖浓度为18%时,发酵周期约为64h,发酵转化率达36.84%,发酵液经离子交换树脂纯化后,可以直接用于生产VB2合成的中间体-N-D-核糖醇基-3,4-二甲苯胺。 相似文献
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微生物混合培养从D山梨醇产生维生素C前体——2-酮基-L-古龙酸 总被引:6,自引:1,他引:5
氧化葡萄糖酸杆菌(Gluconobacter oxydans)SCB329以D-山梨醇为底物培养时可产生微量2-酮基-L-古龙酸;而葡萄糖酸杆菌(Gluconobacter sp.)SCB110能将D-山梨醇以较高效率转化为L-山梨糖,但不产2-酮基-L-古龙酸。将两种微生物在以山梨醇为底物的培养基中混合培养,其代谢产物经分离提纯后进行熔点测定、元素分析、红外吸收光谱测定等,确定其主要的代谢产物是2-酮基-L-古龙酸。 相似文献
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2—KLG产生菌混合发酵特性及最佳混生模式的研究 总被引:4,自引:1,他引:4
氧化葡萄糖酸杆菌合成的2-KLG对巨大芽孢杆菌的生长繁殖具有明显的抑制作用,可缩短其生长周期。发酵体系中巨大芽孢杆菌的存在是氧化葡萄糖酸杆菌的生长繁殖和合成2-KLG所必需的,发酵过程中巨大芽孢杆菌裂解所释放的活性物质可能是刺激氧化葡萄糖酸杆菌合成2-KLG的主要原因。二菌混合发酵需在适宜的混生模式下才可达到最佳效果。 相似文献
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真养产碱菌利用高果糖浆积累聚β-羟基丁酸的研究 总被引:8,自引:0,他引:8
真养产碱菌(Alcaligenes eutrophus)H16能以果糖为碳源在无机合成培养基上积累聚p-羟基丁酸(PHB)。将该菌用富含果糖的高果糖浆(HFS)培养,PHB的积累可达到果糖发酵水平,但发现高浓度的果糖和葡萄糖对菌体生长及PHB积累有抑制作用。采用补料分批培养技术可降低果糖和葡萄糖的抑制。并可大幅度提高产量,菌体干重达16—20g/L,PHB产量7.0—7.6g/L,PHB的产率达0.24g/g果糖。 相似文献
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真养产碱菌(Alcaligenes eutrophus)H16能以果糖为碳源在无机合成培养基上积累聚p-羟基丁酸(PHB)。将该菌用富含果糖的高果糖浆(HFS)培养,PHB的积累可达到果糖发酵水平,但发现高浓度的果糖和葡萄糖对菌体生长及PHB积累有抑制作用。采用补料分批培养技术可降低果糖和葡萄糖的抑制。并可大幅度提高产量,菌体干重达16—20g/L,PHB产量7.0—7.6g/L,PHB的产率达0.24g/g果糖。 相似文献
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Summary A citric acid accumulating strain of Aspergillus niger adapted to grow on gluconic acid lactone as sole carbon source was studied with regards to the enzymatic changes occurring during its adaptive growth and compared with those of the parent strain cultivated on sucrose.Glucose oxidase, glucose dehydrogenase, gluconate dehydrogenase and enzymes of Entner Doudoroff pathway could not be detected in the strain. Gluconokinase was detected in the strain and its inducible nature was established. An adaptive increase of gluconokinase, phosphogluconate dehydrogenase and ribose phosphate isomerase was observed. While the levels of the above enzymes were significantly higher, that of glucose 6-phosphate dehydrogenase were significantly low indicating the repression of the enzyme. Levels of hexokinase and fructose diphosphate aldolase remained more or less the same as that of parent strain. It was inferred from the results that gluconate metabolism occurs via the pentose phosphate pathway following initial phosphorylation.Part of this work was presented at the 8th Annual Microbiological Congress of Association of Microbiologists of India, held in New Delhi 1967. 相似文献
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A transketolase mutant was first isolated from Corynebacterium glutamicum, an organism of industrial importance. The mutant strain exhibited an absolute requirement for shikimic acid or the aromatic
amino acids and vitamins for growth, and also failed to grow on ribose or gluconic acid as sole carbon source, even with the
aromatic supplement. All of these defective properties were fully restored in spontaneous revertants, indicating the existence
of a single transketolase in C. glutamicum that was indispensable both for aromatic biosynthesis and for utilization of these carbohydrates in vivo. The transketolase
mutant accumulated ribulose extracellularly when cultivated in glucose medium with shikimic acid, but no ribose was detected.
Received: 10 April 1998 / Received revision: 26 May 1998 / Accepted: 14 June 1998 相似文献
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Role of sugar uptake and metabolic intermediates on catabolite repression in Bacillus subtilis. 下载免费PDF全文
Many phosphorylated intermediates exert catabolite repression on the enzyme acetoin dehydrogenase in Bacillus subtilis. This was shown with strains that are blocked at different positions in central metabolism when they receive sugars that cannot be metabolized past enzymatic block(s). In the case of sorbitol, transport events were not involved in catabolite repression, for this sugar cannot repress acetoin dehydrogenase in a strain lacking sorbitol dehydrogenase but otherwise able to take up sorbitol. The presence of glucose did not markedly influence the uptake of acetoin. 相似文献
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AbrB modulates expression and catabolite repression of a Bacillus subtilis ribose transport operon. 总被引:2,自引:2,他引:0 下载免费PDF全文
M A Strauch 《Journal of bacteriology》1995,177(23):6727-6731
A Bacillus subtilis ribose transport operon (rbs) was shown to be subject to AbrB-mediated control through direct AbrB-DNA binding interactions in the vicinity of the promoter. Overproduction of AbrB was shown to relieve catabolite repression of rbs during growth in the presence of poorer carbon sources such as arabinose but had much less effect when cells were grown in the presence of glucose, a rapidly metabolizable carbon source. A ccpA mutation relieved catabolite repression of rbs under all conditions tested. One of the AbrB-binding sites on the rbs promoter contains the putative site of action for the B. subtilis catabolite repressor protein CcpA, suggesting that competition for binding to this site could be at least partly responsible for modulating rbs expression during carbon-limited growth. 相似文献
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The concept of a charged membrane bioreactor (CMBR) has been proposed for continuous reactions of enzymatic reduction dependent upon the nicotinamide coenzyme NADP(H). It was found that a composite membrane with a negative charge, NTR 7410, could retain NADP(H) selectively without any chemical modification. Several permeation experiments have revealed that the retainment of a coenzyme is based on electrostatic repulsion of negative charges between the membrane and the phosphate moiety of NADP(H). The retainment ratio was reduced by the addition of inorganic salt, although it could be restored to 0.8 in the presence of albumin. A reactor equipped with a charged membrane as the coenzyme separator module was constructed and used in the continuous production of sorbitol. NADPH-dependent aldose reductase isolated from Candida tropicalis IAM 12202 was used for the production of sorbitol from glucose. The coenzyme oxidized in this reaction was enzymatically regenerated by conjugation with glucose dehydrogenase, together with the coproduction of gluconic acid from glucose. With a substrate conversion of 85%, 100 g/L sorbitol was produced and equimolar gluconic acid was coproduced for more than 800 h, indicating that the reaction was efficiently coupled to the enzymatic regeneration. The initial high retainment ratio of the membrane was almost maintained throughout the entire reaction. Consequently, the turnover number of the coenzyme reached 106,000. 相似文献
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The optimization task was performed using the gluconic acid synthesis by the Acetobacter methanolicusMB 58 strain. The microorganisms were grown continuously on methanol as the growth substrate. After finishing the growth process by the deficiency of N and P, the gluconic acid synthesis was started by adding glucose. The synthesis process was performed continuously. The oxygen transfer rate depended on the gluconic acid concentration. During the growth process, the oxygen transfer rate reached a value of about 13 g O2 · kg?1 · h?1using a 30-l glass fermenter equipped with a 6 blade stirrer and fully baffled. This rate declined to a value of between 2 and 5 g O2 · kg?1 · h?1 in the presence of gluconic acid concentrations above 150 g gluconic acid · kg?1medium. The yield (g gluconic acid · g?1glucose) depended on the gluconic acid concentration and amounted to y = 0.7 in relation to 150 g gluconic acid · kg?1medium and y = 0.8 in relation to 200 g · kg?1medium, respectively. The fermenters were coupled with ultrafiltration moduls (Fa. ROMICON and Fa. SARTORIUS). The biomass concentrations amounted from 5 to 40 g dry mass kg?1medium. The ultrafiltration modules retained the biomass within the fermentation system. A glucose solution (30 to 50 weight percent glucose) was continuously dosed into the fermenter. The retention time was chosen between 2 and 30 h. The gluconic acid synthesis rate reached values of up to 32 g gluconic acid · kg?1 · h?1. Within a range of up to 250 g gluconic acid · kg?1medium, the acid concentration had no influence on the enzyme activity. 相似文献
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细菌纤维素(BC)是一种新型的可再生、可降解的生物高分子材料。为了最大程度的发挥BC生产菌株K.rhaeticus 315的生产能力,本文首先对K.rhaeticus 315进行全基因组测序,通过功能基因的注释、分析碳源代谢流向。结果显示,该菌株碳代谢特征之一是缺乏磷酸果糖激酶的编码基因,不能通过EMP途径代谢糖类碳源,而是主要通过PPP途径和TCA途径代谢碳源,维持菌体生长和BC合成。由于葡萄糖脱氢酶的存在,该菌株在合成BC的同时生成大量副产物—葡萄糖酸。为此,本文通过敲除葡萄糖酸合成酶相关基因,即葡萄糖脱氢酶基因gcd,构建葡萄糖脱氢酶基因缺失重组株(gcd^-),将葡萄糖酸的生成量降低了77%。 相似文献