Synthesis, structure and magnetic properties of (Eu1−xMnx)MnO3−δ

The solid solution (Eu_1−xMn_x)MnO_3−δ (0 ≤ x ≤ 0.126) has been synthesized using a conventional solid-state method.

Copper doped EuMnO3: synthesis, structure and magnetic properties

Solid solution EuMn_1−xCu_xO_3−δ (0 ≤ x ≤ 0.316) crystallizes in the space group Pnma and shows magnetic transitions from about 52 to 20 K.

Improvement of erythromycin production by Saccharopolyspora erythraea in molasses based medium through cultivation medium optimization

In the present work, erythromycin production was carried out in submerged culture using Saccharopolyspora erythraea. Different experiments were conducted to optimize the cultivation medium through the change of carbon and nitrogen sources to cheaper one in order to reduce the cost of medium and to utilize sugar cane molasses as one of major sugar industry by-products in Egypt. It was found that the addition of sugar cane molasses a sole carbon source at a concentration of 60 g/l accompanied by corn steep liquor (as organic N-source) in combination with ammonium sulphate (as inorganic N-source) gave the maximal erythromycin production. The antibiotic production in this medium reached about 600 mg/l which is about 33% higher than the value obtained in glucose based medium. On the other hand, the addition of n-propanol in concentration of 1% (v/v) increased the antibiotic production reaching about 720 mg/l after 144 h. Concluding, the new medium formulation based on cheap carbon source, sugar cane molasses, was a good alternative solution for the production of erythromycin economically.

Alcohol production from starch by mixed cultures of Aspergillus awamori and immobilized Saccharomyces cerevisiae at different agitation speeds

The influence of different agitation speeds on alcoholic fermentation by free and immobilized cells of Saccharomyces cerevisiae in a co-culture with free cells of Aspergillus awamori was investigated. Starch hydrolysis and glucose, glucoamylase and alpha-amylase accumulation in the fermentation medium was affected by agitation speed. Maximum amounts of the enzymes were obtained at 150-200 rpm after 72 h where, maximum growth and glucose accumulations were noticed at 200-300 rpm. Alcohol production was stimulated by low agitation speed (50 rpm) and decreased at higher speeds. The results also showed that the amount of produced alcohol was affected by the time of yeast inoculation. When the inoculation of yeast was carried out after the growth of fungi for 72 h, the amounts of produced alcohol increased by 84, 75, 89 and 68% at 50, 100, 150 and 200 rpm, respectively than that produced when the two organisms were inoculated together at the beginning of the fermentation process. A batch culture of the two organisms produced about 2% (v/v) alcohol from 12% (w/v) corn starch in 72 h at 50 rpm. On the other hand, the immobilized yeast and suspended A. awamori produced more alcohol reaching 3.7% (v/v) at 200 rpm under the same cultivation conditions. The fermentation process was less affected by alginate and cell concentrations of the immobilized yeast. Repeated batch fermentation by co-culture of A. awamori and immobilized yeast cells were successfully used for 12 times without a significant loss in alcohol production.

Influence of inoculum type and cultivation conditions on natamycin production by Streptomyces natalensis

This study demonstrates the effect of cultivation conditions on the production of natamycin. Of these conditions, the effect of oxygen limitation and type of inoculum were extensively investigated. Increasing the shaking speed and decreasing the medium volume improved both the volumetric and specific natamycin production. Also, decreasing the dissolved oxygen level in the cultivation medium through the addition of soluble biopolymer (alginate) resulted in a significant decrease in the natamycin yield without effect on the cell growth. On the other hand, spore inoculum yielded higher concentration of natamycin compared to the vegetative cells by about 40%. The maximal cell productivity based on biomass [Yp/x] of about 0.4 [g/g] was obtained by using shake flask of 50 ml working volume agitated at 200 rpm and the inoculum was in the form of spore 2 x 10(8) spores/ml. These results showed that the production process of natamycin is highly dependent on oxygen level in the cultivation medium and type of inoculum as well.

Optimization of the cultivation medium for natamycin production by Streptomyces natalensis

The effects of certain nutrients on natamycin production by Streptomyces natalensis in submerged batch culture were studied. The production of this antibiotic required glucose in the cultivation medium with a concentration of 20 g/l. On the other hand, the highest antibiotic production was obtained in a cultivation medium containing 0.05 g/l of potassium dihydrogen phosphate. Further increase in phosphate concentration resulted in a significant increase in biomass concomitant with lower antibiotic production. Among different N-sources tested, only ammonium sulphate, sodium nitrate and beef extract were the suitable nitrogen sources in supporting the antibiotic production. Furthermore, a mixture of beef extract and yeast extract (8 g/l and 2 g/l, respectively) exhibited a synergistic effect in enhancing the natamycin production reaching about 1.5 g/l.

The malaria campaign--why not eradication? Interview by Eilif Liisberg and Socrates Litsios

In its first issue in 1980 World Health Forum carried a Round Table on malaria for which Dr M.A. Farid wrote the lead article, reviewing malaria "eradication" between the 1950s and the 1970s. He now gives his personal impressions of those early days of working with WHO to Dr Eilif Liisberg and Dr Socrates Litsios.

Studies of rifamycin production by Amycolatopsis mediterranei cells immobilized on glass wool

Cells of Amycolatopsis mediterranei CBS 42575 were immobilized on glass wool for the production of rifamycins B and SV. Glass wool (CORNING type) of 8 microns in diameter has a better entrapment capacity for microbial cells of microorganism than the other types of glass wool used. The most suitable amount of glass wool was 0.8 g/50 ml. The best initial cell concentration used as inoculum was 40 mg cells/50 ml. Repeated batch production of rifamycins by immobilized cells on glass wool was carried out for 6 repeated batches. The results showed that reduction of batch time from 96 h to 48 h does not decrease rifamycin production by immobilized cells.

Cellulase production on high levels of cellulose and corn steep liquor

Several enhanced cellulase mutants of Trichoderma reesei have been used for cellulase production using corn steep liquor and microcrystalline cellulose as substrates. Under the optimum fermentation conditions on 6% cellulose and 3.6% corn steep liquor Trichoderma reesei Rut C 30 produced high levels of cellulase enzymes 6MC-ase 54 IU/ml, filter paper activity 3.2 IU/ml after 10 days incubation at 28-30 degrees C.

Views and reflections on anti-malaria programmes in the world

The certification of achieved malaria eradication from Taiwan in 1965, and the maintenance of malaria-free status of the country for 25 years, do prove the soundness of the malaria eradication adopted in 1955 by the World Health Assembly, but only when this policy is well understood and well implemented. Certain unique features of Taiwan eradication programme that ultimately lead to its success are cited. The worsening of the malaria situation in the world, and the dismantling of the vertical malaria structures in many countries were highlighted in an article entitled "Malaria Programme from Euphoria to Anarchy" in the WHO forum of 1980. Since then another decade of indifference to the rising tide of malaria, brought about an alarming situation that elicited the 1989 World Health Assembly's resolution on Malaria Control. The underlying causes of this indifference by governments and international bodies concerned with health and socioeconomic development are presented to apprise governments of malarious countries of certain imperative facts that have to be accepted when seriously considering malaria control schemes in their health plans. The need for training future generations of seasoned malariologists is stressed, as well as the need to develop new curricula comprising the experience gained in this field since the dawn of this century. A stress is made on the importance of promoting research, not only on technical problems but also on the social behaviour of rural communities in relation to the acceptance and participation in malaria control programmes. The role of Tropical Diseases Institutes and Research Centres in promoting basic and practical research in the field of malaria is underlined.

Utilization of waste products of dehydrated onion industry for production of fodder yeast by Saccharomyces cerevisiae

One strain of Saccharomyces cerevisiae was selected from different yeasts, isolated from black strap molasses. This microorganism was cultivated on seven fermentation media for the production of protein. Medium I exhibited the highest potentiality for formation of protein. Therefore strain 1 of S. cerevisiae and medium I were used for further studies in the formation of protein. Factors controlling production of protein were explored. The required incubation period for the fermentation process was 72 hrs, while the initial pH value of the medium was 6.0. Sucrose supported the microorganism for higher production of protein (40.96%), while the best concentration of sucrose was shown to be 10.0 g/l. The best inorganic and organic nitrogen sources for protein formation were (NH4)2HPO4, (NH4)3PO4 and yeast extract, respectively. The best concentrations of (NH4)2HPO4 and yeast extract, supporting protein formation, were 5.0 g/l and 10.0 g/l, respectively. Addition of MgSO4, ZnSO4, ferrous ammonium sulphate, copper sulphate, biotin, Ca-pantothenate, thiamine, pyridoxine, and inositol to the synthetic medium did not markedly influence high level of protein formation. Glutamic acid was the best amino acid, supporting protein formation by S. cerevisiae. Onion juice was found to be a good medium, after deletion of inhibitory volatile sulphur organic compounds, for the production of protein by S. cerevisiae. Addition of (NH4)2HPO4 to the best concentration of onion juice assisted the onion medium in production of fodder yeast, containing high level of protein. Addition of MgSO4 to onion juice and (NH4)2HPO4 did not increase the total nitrogen of the biomass. Fodder yeast, produced by onion juice medium, contained more valuable ingredients than fodder yeast, produced by synthetic medium.