Tagesperiodische Resistenzschwankungen gegenα-Strahlen

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Production of 2,3-butanediol in a membrane bioreactor with cell recycle

Summary The production of 2,3-butanediol by Enterobacter aerogenes DSM 30053 was studied in a cell recycle system with a microfiltration module. Emphasis was put on the influence of oxygen supply, cell residence time, dilution rate, and pH. Under optimal conditions a productivity as high as 14.6 g butanediol + acetoin/l per hour was achieved with a product concentration of 54 g/l and a product yield of 88%. This productivity is three times higher than that of an ordinary continuous culture. The achievable final product concentration of a cell recycle system was limited by the accumulation of the inhibiting by-product acetic acid, which increased very rapidly at low dilution rate. To maximize product concentration a fed-batch fermentation was carried out with stepwise pH adaption at high cell density. A final product concentration of 110 g/l was obtained with a productivity of 5.4 g/l per hour and a yield of 97%.     

2,3-Butanediol production by Enterobacter aerogenes in continuous culture: role of oxygen supply

Summary The influence of oxygen on growth and production of 2,3-butanediol and acetoin by Enterobacter aerogenes was studied in continuous culture. At all dilution rates (D) studied cell mass increased steadily with increasing oxygen uptake rate (OUR), hence the micro-aerobic cultivation was energy-limited. The biomass yield on oxygen increased with D which suggests that cells need more energy for maintenance functions at lower D. At each D an optimal OUR giving highest volumetric productivity for the sum of butanediol and acetoin was found. The optimal OUR increased with D. The occurrence of optimal OURs results from the various effects of O₂ on growth and specific productivity. The latter was found to be a linear function of the specific OUR irrespective of D. At optimal OUR the cells proved to have equal specific OURs and equal specific productivities representing a fixed relationship between fermentative and respiratory metabolism. The product yield based on glucose and corrected for biomass formation was 80%. A product concentration as high as 43 g/l was obtained at D =0.1 h^–1 while the volumetric productivity was the highest at D =0.28 h^–1 (5.6 g/l and hour). The findings further indicate that growth and product generation are obviously non-associated phenomena. Hence, high productivities may be achievable by cell recycling and cell immobilisation systems. Offprint requests to: W.-D. Deckwer     

Effects of substrate limitation on product distribution and H2/CO2 ratio inKlebsiella pneumoniae during anaerobic fermentation of glycerol

Product formation during anaerobic degradation of glycerol byKlebsiella pneumoniae DSM 2026, under glycerol limitation and glycerol excess in continugius cultures, has been investigated. Major and minor products and by-products as well as gaseous products were measured. The results indicated a positive correlation between specific glycerol uptake and most product formation rates under glycerol limitation. The production of 1,3-propanediol, lactate, formate, acetate, succinate and the by-products of anaerobic glycerol degradation byK. pneumoniae, acetoin and 2,3-butanediol, was favoured by glycerol excess, while hydrogen generation and ethanol formation were best under glycerol limitation. It was also found that under glycerol limitation the rate of hydrogen evolution was generally higher than the CO₂ production rate while under excess glycerol the reverse was true. Hence, on the basis of the ratio of the specific rates of evolution of H₂ and CO₂ (q _{H 2}/q _{CO 2}), it is possible to infer the existence of glycerol limitation. On the basis of the carbon and available electron balances, which are independent of metabolic pathways, the data are consistent. The NADH₂ balance, which took into consideration the pathways of product formation, was also tested to check the validity of the assumed pathways and to check critically the consistency of the data. Good balances were also obtained.[     

Fermentation of glycerol to 1,3-propanediol and 2,3-butanediol by Klebsiella pneumoniae

Klebsiella pneumoniae was shown to convert glycerol to 1,3-propanediol, 2,3-butanediol and ethanol under conditions of uncontrolled pH. Formation of 2,3-butanediol starts with some hours' delay and is accompanied by a reuse of the acetate that was formed in the first period. The fermentation was demonstrated in the type strain of K. pneumoniae, but growth was better with the more acid-tolerant strain GT1, which was isolated from nature. In continuous cultures in which the pH was lowered stepwise from 7.3 to 5.4, 2,3-butanediol formation started at pH 6.6 and reached a maximum yield at pH 5.5, whereas formation of acetate and ethanol declined in this pH range. 2,3-Butanediol and acetoin were also found among the products in chemostat cultures grown at pH 7 under conditions of glycerol excess but only with low yields. At any of the pH values tested, excess glycerol in the culture enhanced the butanediol yield. Both effects are seen as a consequence of product inhibition, the undissociated acid being a stronger trigger than the less toxic diols and acid anions. The possibilities for using the fermentation type described to produce 1,3-propanediol and 2,3-butanediol almost without by-products are discussed. Received: 4 February 1998 / Received revision: 30 March 1998 / Accepted: 13 April 1998     

Taxonomy of the glycerol fermenting clostridia and description of Clostridium diolis sp. nov

Six Clostridium strains which ferment glycerol to 1,3-propanediol were tested for their taxonomic and phylogenetic relatedness. All but one were known as C butyricum. By physiological tests, 16S rDNA sequences and fatty acid composition two groups were distinguished. The first comprised the strains VPI 3266, DSM 2478 and DSM 523 (C. "kainantoi") and was consistent with the type strain of C. butyricum in almost all characters. The second group comprising the strains DSM 5430, DSM 5431 and E5 was related to C. beijerinckii. The 16S rDNAs of these strains were almost identical with that of the type strain of C. beijerinckii, DSM 791. The DNA-DNA hybridization value of DSM 5431 and ES with C. beijerinckii DSM 791 was markedly but not decisively lower (67 and 72%, respectively). However, there were significant physiological differences to C. beijerinckii which suggested to describe the strains as a separate species, Clostridium diolis with strain SH1 (= DSM 5431) as the type strain. The new species is distinguished from C. beijerinckii, which requires complex nutrients, by its ability to grow in glucose mineral medium with biotin as the only growth factor and by differences in substrate utilization. "C. kainantoi" Takeda and Matsui was recognized as a later synonym of C. butyricum.     

Morphologische,anatomische und zellphysiologische Untersuchungen an Pflanzen vom „Gamma-Feld“ des Brookhaven National Laboratory (USA)

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Chronic Lymphocytic Leukemia Patients Have a Preserved Cytomegalovirus-Specific Antibody Response despite Progressive Hypogammaglobulinemia

Chronic lymphocytic leukemia (CLL) is characterized by progressive hypogammaglobulinemia predisposing affected patients to a variety of infectious diseases but paradoxically not to cytomegalovirus (CMV) disease. Moreover, we found reactivity of a panel of CLL recombinant antibodies (CLL-rAbs) encoded by a germ-line allele with a single CMV protein, pUL32, despite differing antibody binding motifs. To put these findings into perspective, we studied prospectively relative frequency of viremia, kinetics of total and virus-specific IgG over time, and UL32 genetic variation in a cohort of therapy-naive patients (n=200). CMV-DNA was detected in 3% (6/200) of patients. The decay of total IgG was uniform (mean, 0.03; SD, 0.03) and correlated with that of IgG subclasses 1-4 in the paired samples available (n=64; p<0.001). Total CMV-specific IgG kinetics were more variable (mean, 0,02; SD, 0,06) and mean decay values differed significantly from those of total IgG (p=0.034). Boosts of CMV-specific antibody levels were observed in 49% (22/45) of CMV-seropositive patients. In contrast, VZV- and EBV-specific IgG levels decayed in parallel with total IgG levels (p=0.003 and p=0.001, respectively). VZV-specific IgG even became undetectable in 18% (9/50) of patients whereas CMV-specific ones remained detectable in all seropositive patients. The observed CMV-specific IgG kinetics were predicated upon the highly divergent kinetics of IgG specific for individual antigens - glycoprotein B-specific IgG were boosted in 51% and pUL32-specific IgG in 32% of patients. In conclusion, CLL patients have a preserved CMV-specific antibody response despite progressive decay of total IgG and IgG subclasses. CMV-specific IgG levels are frequently boosted in contrast to that of other herpesviruses indicative of a higher rate of CMV reactivation and antigen-presentation. In contrast to the reactivity of multiple different CLL-rAbs with pUL32, boosts of humoral immunity are triggered apparently by other CMV antigens than pUL32, like glycoprotein B.