Abstract: The species identification, culture conditions optimization and secondary metabolites of an antibacterial marine actinomycete HN1-131 isolated from mangrove sediment in Hainan were investigated. Based on the 16S rDNA sequence analysis and morphological observation, strain HN1-131 was identified asStreptomyces tanashiensis. The results of single factor test showed that both the GS and YG media were most suitable for the growth, secondary metabolism and active metabolites production of the strain HN1-131. Orthogonal experiments showed that soluble starch content in GS medium had a significant impact on the growth and antibacterial substances synthesis of strain HN1-131, while 60‰ of NaCl significantly inhibited the production of antibacterial active substances. Through orthogonal experimental optimization, the weight of crude extracts of this strain increased by 30.0% and its antibacterial activity against CV12472 and SA43300 increased by 35.6% and 14.5%, respectively. Through GC-MS analysis, thirteen possible compounds were identified from the active components, among which several compounds including diisooctyl phthalate, 2,2′-methylenebis \[4-methyl-6-tert-butylphenol\] and kenparone exhibited antibacterial, anti-tumor, or antioxidant activities. The relative abundance changes of diisooctyl phthalate and 2,2′-methylenebis\[4-methyl-6-tert-butylphenol\] in the crude extract before and after optimization were consistent with the changes of antibacterial activity of the crude extract. The strain HN1-131 had excellent antibacterial activity and abundant active metabolites, which might be a good source for active substances and provided a basis for the development of mangrove microbial resources.

Key words: Streptomyces tanashiensis, mangrove, antibacterial activity, secondary metabolites, culture conditions optimization