Experiences with a new type of microcarrier

Summary Two new microcarriers were tested and showed good properties in cell attachment, cell growth and production of Human--Interferon. Cell densities up to 5·10⁶ cells/ml on microcarriers were reached in 1 l bioreactors.     

The influence of forskolin on the metabolism of ecdysone and 20-hydroxyecdysone in isolated fat body of the blowfly, Calliphora vicina

Rates of ecdysone and 20-hydroxyecdysone metabolism were measured by radio-assay in an in vitro system containing fat body isolated from blowfly larvae. The addition of forskolin which is known to stimulate artificially the intracellular adenylate cyclase system led to decreased rates of conversion of ecdysone into 20-hydroxyecdysone (= hormone activation) and of 20-hydroxyecdysone further to other metabolites (= hormone inactivation). The effect of forskolin was dose-dependent and reversible. Extracts prepared from larval brains were also tested. Some of them had the same effect as forskolin. It is concluded that the reactions leading from ecdysone to 20-hydroxyecdysone and further to hormonally inactive ecdysteroids are modulated by the intracellular level of cyclic nucleotides. We propose that a neurohormone is involved in the control of the reactions of the ecdysone metabolism. The observed new principle may contribute to the control of the titer of moulting hormone.     

Improved ethanol production from xylose with glucose isomerase and Saccharomyces cerevisiae using the respiratory inhibitor azide

Summary Ethanol was produced from xylose, using the enzyme glucose isomerase (xylose isomerase) and Saccharomyces cerevisiae. The influence of aeration, pH, enzyme concentration, cell mass and the concentration of the respiratory inhibitor sodium azide on the production of ethanol and the formation of by-products was investigated. Anaerobic conditions at pH 6.0, 10 g/l enzyme, 75 g/l dry weight cell mass and 4.6 mM sodium azide were found to be optimal. Under these conditions theoretical yields of ethanol were obtained from 42 g/l xylose within 24 hours.In a fed-batch culture, 62 g/l ethanol was produced from 127 g/l xylose with a yield of 0.49 and a productivity of 1.35 g/l·h.     

Effects of oxygen and chloramphenicol on Frankia nitrogenase activity

The kinetics of asymbiotic nitrogenase activity in three strains of the actinomycete Frankia were studied. Decay rates for enzyme activity were determined by adding chloramphenicol to active acetylene-reducing cells and measuring the time required for all activity to cease. Synthesis rates were measured by bubbling oxygen through actively-reducing cells (which totally destroyed all activity) and then measuring the time required for activity to return to normal. Decay rates (t _1/2) for these three strains were approximately 30 to 40 min. Synthesis rates were slower and initial nitrogenase activities were recorded about 110 min (DDB 011610) or 210 min (DDB 020210 and WgCc1.17) after return to air-equilibrated cultures. Frankia strain WgCc1.17 showed a greater sensitivity to oxygen and nitrogenase activity was totally lost when cells were bubbled only with atmospheric concentrations of oxygen. The results presented here indicate that nitrogenase activity turnover time is relatively rapid, on the order of minutes rather than hours or days. However, regulation of nitrogenase activity will differ from one strain to another and asmmbiotic characterization will be useful for understanding nitrogenase regulation in the bacterial-plant symbiosis.Contribution no. 879 from the Battelle-Kettering Laboratory     

A Novel abscisic acid metabolite from cell suspension cultures of Nigella damascena

The structure of a novel abscisic acid metabolite isolated from cell suspension cultures of Nigella damascena fed [2-¹⁴C]abscisic acid was iden     

Studies on Microbial Ribonucleic Acid VI. Appearance of Methyl-deficient Transfer Ribonucleic Acid During Logarithmic Growth of Saccharomyces cerevisiae

Transfer ribonucleic acid (tRNA) that is deficient in methyl groups may be detected in logarithmically growing Saccharomyces cerevisiae. The amount of methyl-deficient tRNA is not constant throughout the logarithmic phase, but is maximal about one generation before the onset of the late growth phase. During this latter phase, the tRNA is fully methylated. The methyl-deficient tRNA is present during a period of high metabolic activity of the cell, characterized by increased RNA and protein content.