Effect of gamma radiation on the survival of fungal and actinomycetal florae contaminating medicinal plants.

This study evaluates the effect of gamma radiation on the viability of fungi and actinomycetes that contaminate medicinal plants. The relationship between the total lipids of some fungi and actinomycetes and their sensitivity to gamma radiation is also investigated. The date reveal that the viable counts of these florae decrease approximately exponentially with the radiation dose, the effective dose for the elimination of these microorganisms being about 5 kGy for all the medicinal plants under study. Response of pure cultures of fungi and actinomycetes isolated from medicinal plants to increasing absorbed doses of gamma radiation indicate that an increase in radioresistance is in the following order: Streptomyces rimosus, Fusarium solani, Nocardia kuroishii. F. oxysporum, A. fumigatus, A. flavus, A. parasiticus and A. ochraceus. The total lipid contents of molds and actinomycetes have been reported to be increased by increasing the radio-resistance of microorganisms, and hence there is a relationship between the radio-sensitivity of microorganisms and the total lipid mass of flora mycelia.

Mode and extent of degradation of adenosine and guanosine by extracts of Aspergillus terricola.

The mode of degradation of adenosine by extracts of Aspergillus terricola was suggested to be affected preliminary by adenosine deaminase to inosine and the resulting ribonucleoside was then degraded hydrolytically to give hypoxanthine and ribose. With regard to guanosine, the same extracts could initially catalyze the hydrolytic cleavage of guanosine to guanine and ribose. The resulting base was then deaminated to give xanthine by guanine deaminase. Addition of arsenate to the reaction mixture or dialyzing the extract did not affect the observed hydrolytic activity indicating the absence of phosphorylase activity or phosphorylase-phosphatase activities in the extracts.

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.

Hydrolytic cleavage of purine ribonucleosides by extracts of Aspergillus terricola.

Cell-free extracts of nitrate-grown Aspergillus terricola could catalyze the hydrolytic cleavage of the N-glycosidic bond of adenosine, guanosine and inosine optimally at pH 4 and 50 degrees C. Incubation of the extracts at 60 degrees C for 60 minutes caused about 86%, 67% and 54% loss of activity respectively. The similarities between the pH or the temperatures profiles indicate that the hydrolytic cleavage of these purine ribonucleosides might be effected by one hydrolase. The results obtained indicate the absence of evidence for the involvement of an SH group(s) in the catalytic site. CoSO4 and CuSO4 showed a remarkable inhibiting effect on enzyme activity. The apparent Km values of the ribonucleoside hydrolase for adenosine, guanosine and inosine were calculated from Lineweaver--Burk plots and found to be 20, 22.2 and 10 x 10(-3)M respectively.

Properties of adenosine deaminase in extracts of Asperigillus terricola.

Cell-free extracts of nitrate-grown Aspergillus terricola catalyze the hydrolytic deamination of adenosine to inosine at maximum rate at pH 6.5 and 50 degrees C. Incubation of the extracts at 60 degrees C for 30 minutes caused about 66.7% loss in activity. Results indicated the involvement of SH groups in the catalytic site of adenosine deaminase. Frequent freezing and thawing of the enzyme preparation for three days (3 times) resulted in about 47% loss in activity. The enzyme is also inhibited by EDTA indicating that adenosine deaminase is a metaloenzyme. MgCl2 and CoSO4 had a remarkable activating effect, whereas MnCl2 showed a slight inhibitory effect on enzyme activity. The apparent Km value was calculated for adenosine and found to be 6.66 x 10(-3) M, which indicates the greater affinity of adenosine deaminase for adenosine.