| Summary: | Background: The cold-adapted <i>Idiomarina</i> sp. 185 from Antarctic shoreline sediment and the mesophilic <i>Idiomarina</i> sp. A19 from the brackish Lake Faro (Italy) were screened for their efficiency in biosurfactant production by a temperature-mediated approach, when grown in rich culture medium and mineral medium supplemented with biphenyl. Methods: oxidation of polychlorobiphenyls and standard screening tests were performed, i.e., E<sub>24</sub> index detection, surface tension measurement, blood agar plate and C-TAB agar plate. Results: During incubation in rich medium, the strain <i>Idiomarina</i> sp. A19 produced an excellent stable emulsion, recording an E<sub>24</sub> of 73.5%. During growth in mineral medium, isolates showed good efficiency in at least one performed condition by showing species-specific differences related to optimum temperature. In the presence of biphenyl, both <i>Idiomarina</i> isolates created stable emulsions (E<sub>24</sub> ≈ 47.5 and 35%, respectively), as well as surface tension reductions of 30.05 and 35.5 mN/m, respectively. Further differences between isolates were observed by phenotypic characterization. The genome mining approach on available deposited genome sequences for closest relatives offered further insights about the presence of genes for biphenyl degradation, especially for microorganisms derived from different extreme environments. Conclusions: Our results allowed for an interesting comparison which underlined differences in metabolic patterns and in the kinetics of BS production, probably due to the different origins of the strains.
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