Phenotypic characterization for bioremediation suitability of isolates from Southern Tunisian tannery effluent

• Published in: Microbiological research 2024-08, Vol.285, p.127771-127771, Article 127771
• Main Authors: Lejri, Rokaia, Ellafi, Ali, Valero Tebar, Juan, Chaieb, Mohamed, Mekki, Ali, Džunková, Mária, Ben Younes, Sonia
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Antibiotic resistance; Bacillus - classification; Bacillus - genetics; Bacillus - isolation & purification; Bacillus - metabolism; Biodegradation, Environmental; Biofilm; Biofilms - growth & development; Bioremediation; DNase activity; Enterococcus faecium - genetics; Enterococcus faecium - isolation & purification; Enterococcus faecium - metabolism; Exoenzymes; Hemolysis; Hydrophobic activity; Hydrophobic and Hydrophilic Interactions; Industrial Waste; Metals, Heavy - metabolism; Phenotype; Phenotypic extended-spectrum β-lactamase; Phylogeny; Slime-producing bacteria; Tannery effluents; Tanning; Tunisia; Wastewater - microbiology; Water Pollutants, Chemical - metabolism
• ISSN: 0944-5013; 1618-0623
• DOI: 10.1016/j.micres.2024.127771

Effluents from the leather tanning industry contain diverse pollutants, including hazardous heavy metals, posing threats to public health and the surrounding environment. Indigenous bacterial isolates can represent an eco-friendly approach for tannery wastewater treatment; however, phenotypic characterization is necessary to determine whether these strains are suitable for bioremediation. In the present study, we analyzed seven new Enterococcus faecium strains and two new Bacillus subtillis strains isolated from effluents from the Southern Tunisian Tannery (ESTT). We evaluated phenotypic features beneficial for bioremediation, including biofilm formation, hydrophobicity, and exoenzyme activities. Additionally, we examined characteristics naturally occurring in environmental bacteria but less desirable in strains selected for bioremediation, such as antibiotic resistances and pathogenicity indicators. The observed phenotypes were then compared with whole-genome analysis. We observed biofilm production in two slime-producing bacteria, B. licheniformis RLT6, and E. faecium RLT8. Hydrophobicity of E. faecium strains RLT1, RLT5, RLT8, and RLT9, as well as B. licheniformis RLT6 correlated positively with increasing ESTT concentration. Exoenzyme activities were detected in E. faecium strains RLT2, RLT4, and RLT7, as well as B. licheniformis RLT6. As anticipated, all strains exhibited common resistances to antibiotics and hemolysis, which are widespread in nature and do not hinder their application for bioremediation. Importantly, none of the strains exhibited the pathogenic hypermucoviscosity phenotype. To the best of our knowledge, this is the first report consolidating all these phenotypic characteristics concurrently, providing a complete overview of strains suitability for bioremediation. The study evaluates the bioremediation potential of seven Enterococcus faecium strains and two Bacillus subtillis strains isolated from the effluents from the Southern Tunisian tannery (ESTT), which pose threats to public health and environmental integrity. The analysis primarily examines the phenotypic traits crucial to bioremediation, including biofilm formation, hydrophobicity, and exoenzyme activities, as well as characteristics naturally occurring in environmental bacteria related to heavy metal resistance, such as antibiotic resistances. Several strains were found to have high bioremediation potential and exhibit only antibiotic resistances commonly found in nature, en