<i>Streptomyces luridus</i> So3.2 from Antarctic soil as a novel producer of compounds with bioemulsification potential

<div><p>The present study aimed to identify novel microbial producers of bioemulsificant compounds from Antarctic soils. Fifty-nine microbial strains were isolated from five different locations at South Shetland Islands, Antarctica, and screened for biosurfactant production by β-hemolytic activity. Strain So 3.2 was determined as bioemulsifier-producer and identified by phenotypic and molecular characterization as <i>Streptomyces luridus</i>. Emulsification activity, oil displacement method and drop-collapsing test were performed to evaluate the biosurfactant activity with different oils and hydrocarbons using two different culture media (Luria Bertani and Bushnell Haas in the presence of different carbon sources: glucose, glycerol, olive oil and n-Hexadecane). Cell free supernatant of Bushnell Haas culture supplemented with n-Hexadecane showed the best results for all tests. Emulsification of hydrocarbons exceeded 60%, reaching up to 90% on oil with high API grade, while displacement tests ranged from 8 cm to 4 cm in diameter according the culture media and tested oils. Our results revealed that <i>Streptomyces luridus</i> So3.2 is able to produce bioemulsifiers capable of emulsifying hydrocarbons and oils, which could be used in different biotechnological applications, particularly for bioremediation of environments contaminated by oil leaks.</p></div

Reactions of type strain in the APIZYM test.

<p>Reactions of type strain in the APIZYM test.</p

Selection of bacterial strains producing active surface molecules.

<p>Selection of bacterial strains producing active surface molecules.</p

Different sampling sites.

<p>A: Peninsula Byers (<i>Colobanthus quitensis</i> rhizosphere); B: Fildes Bay-Julio Escudero Base; C: Robert Island (<i>Deschampsia antarctica</i> rhizosphere); D: Doumer Island-Yelcho Base; E: Fildes Bay-Escudero Base.</p

Mass spectroscopy (LC-MS) spectra of the purified bioemulsifier from <i>Streptomyces luridus</i> So3.2 strain.

<p>Mass spectroscopy (LC-MS) spectra of the purified bioemulsifier from <i>Streptomyces luridus</i> So3.2 strain.</p

Neighbor-joining dendrogram based on 16S rRNA sequence of strain So3.2 and type strains from <i>Streptomyces</i> genus.

<p>The optimal tree with the sum of branch length = 0.17933430 is shown. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are shown next to the branches. The evolutionary distances were computed using the Maximum Composite Likelihood method and are in the units of the number of base substitutions per site.</p

Emulsification index (E24) produced by supernatant of the strain <i>Streptomyces</i> So3.2 in BH with n-Hexadecane and LB culture medium.

<p>In A, against different hydrocarbons. In B different oil results are shown. Data are given as the mean ± SD for n = 3 samples.</p

Sampling sites and number of bacterial strains isolated.

<p>Sampling sites and number of bacterial strains isolated.</p

Characteristic of bioemulsifiers from <i>Streptomyces</i> genus.

<p>Characteristic of bioemulsifiers from <i>Streptomyces</i> genus.</p

Evaluation of the surface-active biomolecules production by <i>Streptomyces luridus</i> So3.2 on different culture media and carbon sources.

<p>Evaluation of the surface-active biomolecules production by <i>Streptomyces luridus</i> So3.2 on different culture media and carbon sources.</p