The antibacterial activity and silk dyeing of the crude pigment extract from J4 actinobacteria strain

Actinobacteria represent a vast variety of prokaryotic microbes that produce a diverse group of secondary metabolites used in medical, agricultural, and industrial applications. The objectives in this study were to investigate the antibacterial activities and potential for silk dyeing of the crude extract from the actinobacterial strain J4. Initially, the antibacterial activities of the crude pigment extracts obtained from the actinobacterial strain J4 isolated from the wasp’s nest were determined. To extract the water-insoluble pigments used for antibacterial activity testing via the agar well diffusion method, ethyl acetate was applied during the pigment extraction. These extracts showed an inhibitory effect against Salmonella Typhimurium TISTR1472, Bacillus subtilis PSRU-01, and Enterococcus faecalis TISTR459. Secondly, evaluation of silk dyeing was carried out. We used the extractant as 70 % (v/v) ethanol in the alternative extraction process when the strain J4 was cultivated by solid-state fermentation with broken-milled rice to prepare actinobacterial dye for silk dyeing. The pigment extract obtained was tested for color stability based on washing methods, and the sensitivity to light was determined according to ISO105-C06:2010(E) and ISO 105-B02:2014(E), respectively. The color stability and sensitivity of the pigment extract to washing showed scores between 3-5, and the sensitivity to light demonstrated scores between 3-4. Taxonomically, the strain J4 was dark-violet colonies, and its water-soluble pigment diffused on sodium caseinate agar (SCA). To identify the strain J4, the phylogenetic identification based on partial sequencing of 16S rDNA was applied. The identification result indicated that the strain J4 was closely related to Streptomyces coacervatus (99.8% sequence similarity). In future, antibacterial activities of the crude extracts obtained from actinobacteria strain J4 should be tested with other food-borne pathogens. The development of Streptomyces dyes should also focus on the stability of the dyes during the silk dyeing process.