Antioxidant Capacities and Total Phenolic Contents of Selected Actinomycetes sp.

Abstract

Objective: To investigate antioxidant activity and the optimal condition for antioxidant production from actinomycetes isolate SR3.97. Method: Cultivation of actinomycetes isolate SR3.97 was done by inoculation into maltose yeast extract (MYEB), tryptone-yeast extract broth (ISP-1)and Bennett’s broth (BN). The cultures were incubated on rotary shaker at 200 rpm, 37 ºC, for 7 days. The culture supernatants were obtained and subsequently lyophilized, and further subject to the analysis of antioxidant activity by 1,1-diphenyl-2-picrylhydrazyl radical-scavenging (DPPH) method. Actinomycetes isolate was cultured in select liquid medium and the lyophilized portion was taken for analysis of antioxidant activity by DPPH, 2,2’-azinobis (3-ethylbensothiazoline-6-sulfonic acid) assay (ABTS), Ferric-reducing Antioxidant Power (FRAP) assay and total phenolic content. Optimal conditions for antioxidant production on initial pH at 4, 5, 6, 7, 8 and 9, temperatures at 25, 30, 35, 37, 40 and 45 ºC and incubation time of 1, 3, 5, 7, 9, 11, 13, 15 days were investigated. Identification of actinomycetes isolate SR3.97 was carried out based on 16S rRNA sequence analysis. Results: Actinomycetes isolate SR3.97 was selected as the best isolate for producing antioxidant in MYEB medium. The MYEB medium exhibited antioxidant activity as measured by DPPH, ABTS and FRAP analysis with IC50 values of 71.52 ± 0.76 µg/ml, 35.88 ± 0.84 µg/ml and 156.91 ± 1.34 µM Fe(II)/mg, respectively and total phenolic content of 57.82 ± 0.1 µg GEA/mg. The optimal culture conditions for antioxidant production were initial culture pH at 7, incubation temperature of 37ºC, and incubation time for 7 days. Actinomycetes isolate SR3.97 was identified based on 16S rRNA gene sequence analysis. The isolate was 99.40% resembled with Streptomyces chrysomallus subsp. fumigatus NBRC 15393T. Conclusion: Difference antioxidant levels were produced from actinomycetes isolate SR3.97 when different media were used. The temperature, pH and incubation time affected antioxidant production. Keywords: Actinomycetes, Antioxidant, Phenolic compound, Streptomyces chrysomallus