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排序方式: 共有288条查询结果,搜索用时 218 毫秒
21.
Delaunay S Lapujade P Engasser JM Goergen JL 《Journal of industrial microbiology & biotechnology》2002,28(6):333-337
In order to test the temperature sensitivity of glutamate production metabolism, several temperature shifts, from 33 to 37,
38, 39, 40 or 41°C, were applied to the temperature-sensitive strain, Corynebacterium glutamicum 2262, cultivated in a 24-h fed-batch process. Whereas glucose was entirely dedicated to biomass synthesis when cells were
grown at 33°C, applying temperature upshocks, whatever their range, triggered a redistribution of the carbon utilisation between
glutamate, biomass and lactate production. Although increasing the culture temperature from 33 to 37, 38, 39 or 40°C resulted
in final glutamate titers superior to 80 g/l, temperatures resulting in the best chanelling of the carbon flow towards glutamic
acid synthesis were 39 and 40°C. Moreover, this study showed that the higher the temperature, the slower the growth rate and
the higher the lactate accumulation. Journal of Industrial Microbiology & Biotechnology (2002) 28, 333–337 DOI: 10.1038/sj/jim/7000251
Received 26 September 2001/ Accepted in revised form 23 February 2002 相似文献
22.
Fed-batch cultures of Bacillus licheniformis produced poly--glutamic acid (PGA), a water-soluble biodegradable polymer. PGA reached 35 g l–1 with a productivity of 1 g l–1 h–1 by pulsed-feeding of citric acid (1.44 g h–1) and l-glutamic acid (2.4 g h–1) when citric acid was depleted from the culture medium. 相似文献
23.
Ubiquinone (Coenzyme Q; abbreviation, UQ) acts as a mobile component of the respiratory chain by playing an essential role
in the electron transport system, and has been widely used in pharmaceuticals. The biosynthesis of UQ involves 10 sequential
reactions brought about by various enzymes. In this study we have cloned, expressed the decaprenyl diphosphate synthase, designated
dps gene, from Agrobacterium tumefaciens, and succeeded in detecting UQ-10 in addition to innate UQ-8 in Escherichia coli. Furthermore, the production of UQ-10 was higher than UQ-8. To establish an efficient expression system for UQ-10 production,
we used genes, including ubiC, ubiA, and ubiG involved in UQ biosynthesis in E. coli, to construct a better co-expression system. The expression coupled by dps and ubiCA was effective for increasing UQ-10 production by five times than that by expressing single dps gene in the shake flask culture. To study for a large-scale production of UQ-10 in E. coli, fed-batch fermentations were implemented to achieve a high cell density culture. A cell concentration of 85.40 g/L and 94.58
g/L dry cell weight (DCW), and UQ-10 content of 50.29 mg/L and 45.86 mg/L was obtained after 32.5 h and 27.5 h of cultivation,
subsequent to isopropyl-β-d-thiogalactopy ranoside and lactose induction, respectively. In addition, plasmid stability was maintained at high level throughout
the fermentation. 相似文献
24.
主要考察流加培养基中不同营养成分、流加起始时间及初始接种密度对11G-S细胞无血清流加培养的影响。在研究中以悬浮适应的表达尿激酶原 (Pro-urokinase,Pro-UK) CHO工程细胞系11G-S为研究对象,在100 mL的摇瓶中无血清悬浮流加培养11G-S细胞,同时以活细胞密度、细胞活力及Pro-UK活性为评价依据。结果表明在培养基中氨基酸、无血清添加成分及无机盐对促进细胞生长、细胞活力维持及蛋白表达起着较为重要的作用;且流加起始时间为72 h及初始接种密度为3×105~4×105 cells/ 相似文献
25.
Tiejun Liu Shigenobu Miura Tomohiro Arimura Min-Yi Tei Enoch Y. Park Mitsuyasu Okabe 《Biotechnology and Bioprocess Engineering》2005,10(6):522-527
Various processes which producel-lactic acid using ammonia-tolerant mutant strain,Rhizopus sp. MK-96-1196, in a 3 L airlift bioreactor were evaluated. When the fed-batch culture was carried out by keeping the glucose
concentration at 30 g/l, more than 140 g/l ofl-lactic acid was produced with a product yield of 83%. In the case of the batch culture with 200 g/l of initial glucose concentration, 121 g/L ofl-lactic acid was obtained but the low product yield based on the amount of glucose consumed. In the case of a continuous culture,
1.5 g/l/h of the volumetric productivity with a product yield of 71% was achieved at dilution rate of 0.024 h−1. Basis on these results three processes were evaluated by simple variable cost estimation including carbon source, steam,
and waste treatment costs. The total variable costs of the fed-batch and continuous cultures were 88% and 140%, respectively,
compared to that of batch culture. The fed-batch culture with highl-lactic acid concentration and high product yield decreased variable costs, and was the best-suited for the industrial production
ofl-lactic acid. 相似文献
26.
Aims: To investigate the effects of pH stress coupled with cysteine addition on glutathione (GSH) production in the treatment of high cell density culture of Candida utilis. Methods and Results: We have previously observed that most Candida utilis cells remained viable after being subjected to pH at 1·2 for 3 h and that some intracellular GSH leaked into the medium. A cysteine addition strategy was applied in fed‐batch production of GSH. A single cysteine addition resulted in higher GSH yield than two separate additions without pH stress. An increase in intracellular GSH content triggered inhibition of γ‐glutamylcysteine synthetase (γ‐GCS). A strategy that combines cysteine addition with low‐pH stress was developed to relieve the inhibition of γ‐GCS. Conclusion: Without pH stress, single shot and double shot cysteine addition yielded a total GSH of 1423 and 1325 mg l?1. In comparison, a low‐pH stress counterpart resulted in a total GSH of 1542 and 1730 mg l?1, respectively. With low‐pH stress, we observed GSH secretion into the medium at 673 and 558 mg l?1 and an increase in the γ‐GCS activity by 1·2‐ and 1·5‐fold, respectively. The specific GSH production yield increased from 1·76% to 1·91% (w/w) for single shot, and 1·64% to 2·14% for double shots. Significance and Impact of the Study: Low‐pH shift was applied to alleviate the feedback inhibition of intracellular GSH on γ‐GCS activity by secreting GSH into the medium. This strategy is coupled with cysteine addition to enhance GSH production in Candida utilis. 相似文献
27.
G. Amin S. Alotaibi Narmen A. Youssef W. D. Saleh 《World journal of microbiology & biotechnology》2008,24(11):2465-2471
In an attempt to develop a cost-effective process for bioinsecticide production by B. thuringiensis, the feeding regime during aerobic cultivation of the bacterium was investigated and optimized. The process was designed
as a two-stage process; a first stage of active growth, where glucose and other nutrients were adequately supplied to the
growing cells over 12 h, followed by a second stage of 2 h for spore formation and toxin release. In order to maximize spore
and toxin yield and productivity, different quantities of glucose and nutrients were fed separately to the growing cells in
four different fermentation runs. In all runs, glucose was converted to bacterial biomass during the first stage and subsequently
to spores and crystal protein during the second phase. The best results were obtained with a fermentation run supplied with
190 g glucose in 1500 ml. Up to 20.1 g of bacterial insecticides/l were recovered from fermentation broth with a glucose to
toxin conversion yield of 0.159 g/g. Also, a markedly high spore concentration of 2.31 × 1012 c.f.u./ml was obtained. The spore–crystal protein mixture obtained was tested for its insecticidal activity against three
of the most agronomically important pests. Among the bioinsecticide-treated insect pests, Egyptian cotton leafworm, Spodoptera littoralis was the most susceptible pest with the lowest LC50 of the bioinsecticides against its larval instar and the highest virulence against adults emerged later on from the surviving
larvae. 相似文献
28.
29.
Ralstonia eutropha NCIMB 11599 and ATCC 17699 were grown, and their productions of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] compared. In flask cultures ofR. eutropha NCIMB 11599, cell concentration, P(3HB-co-4HB) concentration and polymer content decreased considerably with increases in the γ-butyrolactone concentration, and the
4HB fraction was also very low (maximum 1.74 mol%). In fed-batch cultures ofR. eutropha NCIMB 11599, glucose and γ-butyrolactone were fed as the carbon sources, under a phosphate limitation strategy. When glucose
was fed as the sole carbon source, with its concentration controlled using an on-line glucose analyzer, 86% of the P(3HB)
homopolymer was obtained from 201 g/L of cells. In a two-stage fed-batch culture, where the cell concentration was increased
to 104 g/L, with glucose fed in the first step and constant feeding of γ-butyrolactone, at 6 g/h, in the second, final cell
concentration at 67 h was 106 g/L, with a polymer content of 82%, while the 4HB fraction was only 0.7 mol%. When the same
feeding strategy was applied to the fedbatch culture ofR. eutropha ATCC 17699, where the cell concentration was increased to 42 g/L, by feeding fructose in the first step and γ-butyrolactone
(1.5 g/h) in the second, the final cell concentration, polymer content and 4HB fraction at 74 h were 51 g/L, 35% and 32 mol%,
respectively. In summary,R. eutropha ATCC 17699 was better thanR. eutropha NCIMB 11599 in terms of P(3HB-co-4HB) production with various 4HB fractions. 相似文献
30.
构建了一种纤维床反应器(FBB), 并将其应用于丙酸的生产。将棉纤维绕成桶状, 固定于反应器中, 即可用于丙酸固定化发酵。以40 g/L的葡萄糖为碳源, 与游离细胞相比, 利用FBB生产丙酸, 丙酸产量由14.58 g/L提高至20.41 g/L, 发酵时间由120 h缩短至60 h。研究了不同糖浓度条件下FBB生产丙酸情况, 并将补料策略应用于丙酸发酵中。结果表明: 补料发酵能够有效改善Propionibacterium freudenreichii CCTCC M207015在高糖条件下丙酸对葡萄糖转化率较低、副产物较多的问题。经补料发酵280 h, 丙酸产量达45.91 g/L, 丙酸质量约占有机酸总质量比例为72.31%。 相似文献