Screening for Antimicrobial Agent Production of Some Microalgae in Freshwater

摘要

In this study, 10 microalgae strains isolated from different freshwater reservoirs situated in various topographies in Turkey were tested in compliance with the agar-well diffusion method for their antimicrobial agent production on various organisms (Bacillus subtilis ATCC 6633, Bacillus thuringiensis RSKK 380, Bacillus cereus RSKK 863, Bacillus megaterium RSKK 578, Yersinia enterocolitica ATCC 1501, Escherichia coli ATCC 11230, Staphylococcus aureus ATCC 25923, Micrococcus luteus NRLL B-4375, Micrococcus flavus, Pseudomonas aeruginosa ATCC 29212, Saccharomyces cerevisiae ATCC, Candida albicans ve Candida tropicalis). The findings in this study reveal that activity is maintained against antimicrobial activity of acetone and ether extracts on Gram-negative bacteria; methanol extracts on Gram-positive bacteria; ethanol extracts on both Gram-positive and Gram-negative organisms. Chloroform extracts, on the other hand, were not found to reveal any antimicrobial activity. In addition, Oscillatoria sp. ve Chrococcus sp. were found to have antifungal activity on yeasts. Introduction One potential commercial application of microalgae derived compounds that has, as yet, received little attention is the area of pharmaceuticals, antibiotics and other biologically active compounds. Both cell extracts and extracts of the growth media of various unicellular algae (e.g. Chlorella vulgaris, Chlamydomonas pyrenoidosa) have been proved to have antibacterial activity in vitro against both Gram-positive and Gram-negative bacteria. It has also been reported that a wide range of in vitro active antifungal activities are obtained from extracts of green algae, diatoms and dinoflagellates. Microalgae, such as Ochromonas sp., Prymnesium parvum, and a number of blue-green algae produce toxins that may have potential pharmaceutical applications (Borowitzka and Borowitzka, 1992).Biologically active substances were proved to be extracted by microalgae. Various strains of cyanobacteria are known to produce intracellular and extracellular metabolites with diverse biological activities such as antialgal, antibacterial, antifungal and antiviral activity. Temperature of incubation, pH of the culture medium, incubation period, medium constituents and light intensity are the important factors influencing antimicrobial agent production (Noaman et al., 2004).It is the main objective of this study to test 10 microalgae isolated from various freshwater reservoirs situated in Turkey for their antimicrobial activities on various microorganisms and optimize the conditions for the production of an antimicrobial agent by microalgae. Materials And Methods Culturing and growth conditionsCollection and isolation of microalgae were made in compliance with Rippka (1988). Micro algae were obtained from Mogan and Burdur Lakes, Kurtbo?azi Dame and from the waste waters of a sugar refinery.Algae were made to increase in number by having been left at BG11 nutrition medium less than 3000 lux light intensity, for 16 h under illumination and 8 h under darkness. Algae were harvested approximately after a 15 day production period.Test organismsThe bacteria and yeast strains (Bacillus subtilis ATCC 6633, Bacillus thuringiensis RSKK 380, Bacillus cereus RSKK 863, Bacillus megaterium RSKK 578, Yersinia enterocolitica ATCC 1501, Escherichia coli ATCC 11230, Pseudomonas aeruginosa ATCC 29212, Micrococcus flavus, Micrococcus luteus NRLL B-4375, Staphylococcus aureus HU 25923, Candida albicans, Candida tropicalis, Saccharomyces cerevisiae and Saccharomyces cerevisiae 2SI TP(3-2)) used in this study were obtained from Culture Collections of the Biotechnology Laboratory at the Department of Biology in Gazi University. While the bacteria strains were incubated into nutrient broth throughout 24 h, the yeast strains were incubated into YEPD throughout 48 h. Dry weight determinationThe cells were separated from culture filtrate by centrifugation and then washed several times with distilled water. Bi