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Current Trends in Biotechnology and Pharmacy Vol. 5 (3) 1282-1297 July 2011, ISSN 0973-8916 (Print), 2230-7303 (Online) 1291 Evidently, the activity was maximal, with an inhibition zone diameter of 37.7 mm, on using sodium chloride at concentration 1 gm %. The antifungal activity at a greater NaCl concentration decreased to reach 30 mm at 4 gm% concentration (Fig. 5). Fig. 6. Growth and anticandidal activity of N.luteus as affected by K 2 HPO 4 Fig. 5 Effect of NaCl concentration Antibiotic biosynthesis by certain halophytic actinomycetes species was found to be optimized at specific NaCl levels (34,35). Similarly, the optimum salt requirement of the strain Streptomyces tanashiensis strain A2D for antibiotic production in medium containing carbon source (glucose) and nitrogen source (soybean). They found that 2 % NaCl was optimum for maximum growth (4.9 mg/ml) as well as antimicrobial compound production (20.9 mg/ml). Further increase in salt concentration reduced the antimicrobial agent biosynthesis (36). Similarly, the role of K 2 HPO 4 on the growth and anticandidal activity was investigated. The productivity of the experimental organism was optimized at 0.1 gm% (Fig. 6). However the depletion of the tested salt from the fermentation medium resulted in a decrease in the antifungal activity. The dry weight yield increased gradually with increasing K 2 HPO 4 concentration until 1.2 gm% after which it remained constant. It was reported that phosphate ions seemed to stimulate the process of primary metabolite production at the expense of secondary metabolite. Also, they reported that the highest dipotassium hydrogen phosphate concentrations studied at 1.6 g/l proved to provide non limiting growth conditions without affecting the antibiotic production (33). It was also noted that the excess PO 4 altered the biochemical composition of the mycelium protoplasm and affected the physiological function of the cell and decreases the biosynthesis of the antibiotic (37). Conversely, phosphate at all concentrations inhibited the production of inhibitory substance(s) by Streptomyces (Ds-104) strain (36). The pH value of the cultivation medium is very important for growth of the microorganism, characteristic of their metabolism and hence for biosynthesis of metabolites. The hydrogen ion concentration may have direct effect on the cell or it may indirectly affect it by varying the dissociation degree of the medium components. Results showed that both production and growth were maximal in the neutral medium either on using buffers or by initial adjustment with 1M HCl and 1M NaOH. It is also noted that trismaleate buffer, although not causing a El-Refai et al
Current Trends in Biotechnology and Pharmacy Vol. 5 (3) 1282-1297 July 2011, ISSN 0973-8916 (Print), 2230-7303 (Online) - Table 3. The TLC profile of the different constituents responsible for the anticandidal activity of N.luteus Band Retention factor (Rf) Inhibition zone (mm) 1 0.07 20 2 0.20 21.5 3 0.47 26 4 0.6 19 5 0.68 13.5 6 0.82 17.5 1292 Table 4. The antitumour activities exhibited by N. luteus bioactive extract Doxorubicin Crude Extract Semi-pure Tested cell line compound 3.96 µg/ml 3.43 µg/ml 2.82 µg/ml HFB4 (normal melanocytes) 5.5 µg/ml 2.51 µg/ml 2.99 µg/ml HEPG2 (liver carcinoma cell line) 2.97 µg/ml 3.28 µg/ml 2.86 µg/ml MCF7 (breast carcinoma cell line) 4.89 µg/ml 3.13 µg/ml 2.4 µg/ml HEP2 (larynx carcinoma cell line) 3.64 µg/ml 2.67 µg/ml 2.82 µg/ml HELA (cervical carcinoma cell line) 3.43 µg/ml 2.82 µg/ml 2.97 µg/ml CACO (colon carcinoma cell line) 3.743 µg/ml 3.74 µg/ml 2.97 µg/ml HCT116 (colon carcinoma cell line) remarkable decrease in activity yet, it resulted in a great decrease in the cell biomass (Data not shown). Increasing the pH value of the culture media of Streptomyces spp. led to an increase in the antifungal production up to certain limit (pH 7.0) above which any increase in the pH value was accompanied by a decrease in the antifungal production and consequently the antagonistic activity. Maximum antifungal activity recorded by Streptomyces strain Ds-104 occurred on using fermentation medium at pH range 7.0-7.5. It afforded an inhibition zone diameter range between 12 and 18 mm. The results obtained by other scientists also assured that the neutral range of pH value enhanced the formation of anticandidal agents from different Streptomyces spp. (36-39). With respect to the role of the agitation rate, the obtained results revealed that the maximum activity was obtained at 200 rpm, though cell biomass yields decreased with increasing the agitation speed being maximal at static state (Fig. 7). Antifungal antibiotic production by the strain Streptomyces rimosus MY02 increased slightly corresponding to agitation rate. But antifungal antibiotic production had no significant differences at 150–200 rpm. Finally, they concluded that the best agitation rate was 180 rpm (40). Studies on the production of actinomycin by Nocardioides luteus
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(December 7-9, 2011) Venue: Karunya
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