UV/VIS, FTIR spectrum and Anticandidial activity of Streptomyces strains

摘要

Two different species Streptomyces aureofaciens and S. albidoflavus were collected from Microbial Type Culture Collection Centre, Chandigarh, India. These two species were extensively studied for their in vitro anticandidial activity. The result indicated that S. aureofaciens was highly active against Candida albicans. The UV spectral analysis of the produced antifungal metabolite of S. aureofaciens and S. albidoflavus showed the absorbance peaks at 240nm. The FTIR spectral study revealed that the ethyl acetate extracts of S. aureofaciens and S. albidoflavus fermentation broth exhibited absorption from 2956 to 2360.7cm-1 and from 3310 to 2358.8cm-1, respectively, which indicate hydroxyl groups and absorption at 1639 cm-1 indicating a double bond of non polyenic compound. Introduction Streptomyces is the largest antibiotic-producing genus in the microbial world discovered so far. The number of antimicrobial compounds reported from the species of this genus per year has increased almost exponentially for about two decades. Recent reports show that this group of microorganisms still remains an important source of antibiotics (Watve et al., 2001). As a result of the increasing prevalence of antibiotic-resistant pathogens and the pharmacological limitations of antibiotics, there is an exigency for new antimicrobial substances. The results of extensive screening have been the discovery of about 4000 antibiotic substances from bacteria and fungi, many of which have found applications in medicine; most of them are produced by Streptomyces (Korn-Wendisch and Kutzner, 1992). To prevent exponential emergence of microorganisms from becoming resistant to the clinically available antibiotics already marketed, a periodic replace of the existing antibiotics is necessary. In the present study, anticandidial activity of compound produced by Streptomyces species was determined and partially characterized. Materials and Methods Collection and maintenance of Actinomycetes strains Two actinomycetes strains such as Streptomyces aureofaciens (MTCC 325) and S. albidoflavus (MTCC 932) were collected from Institute of Microbial Technology, Chandigarh, India. The collected strains were maintained in Streptomyces agar medium (Himedia, Mumbai). Target organism The target organism used in the present study was Candida albicans. antagonism (Slavica et al., 2005)Balanced sensitivity medium (BSM, Difco) plates were prepared and inoculated with individual Streptomyces strains by a single streak of inoculum in the center of the petridish. After 4 days of incubation at 28oC, the plates were seeded with test organism, C. albicans and again incubated the plates for 24 h at 280C. The microbial interactions were analysed by determining the inhibition zone. Fermentation Both actinomycete strains showed activity against C. albicans, so they were grown individually in submerged culture fermentation in 250 ml flask containing 100 ml of various liquid media such as Starch casein, glucose asparagines, glycerol asparagines, sabouraud dextrose, potato dextrose and yeast extract malt extract (Hi Media, Mumbai) to know which liquid medium stimulates maximum antifungal activity (Sahin and Ugar, 2003). The flasks were inoculated with 1ml of active Streptomyces strains and incubated at 37oC for 72 h with shaking at 105t/min. After incubation, the content in each flask was centrifuged at 10,000 rpm for 20 min. The culture supernatants were used as source of anticandidial activity. Isolation of anticandidial compoundFor the detection of anticandidial activity of Streptomyces, the agar well diffusion method was followed according to Kathiresan et al. (2005). The collected organisms were grown well on Yeast extract Malt extract medium for anticandidial activity study. The individual culture broth was centrifuged at 10,000 rpm for 15 min. and then the supernatant was filtered through membrane filter (0.45 mm pore size). Then the filtrate was extracted with ethyl acetate, chloroform an