Characterization of Cr(VI)-reducing indigenous bacteria from a long-term tannery waste-contaminated soil

• Published in: Desalination and water treatment 2024-10, Vol.320, p.100861, Article 100861
• Main Authors: Kabir, Mohammad Mahbub, Akter, Tania, Sabur, Golam Md, Sultana, Nazmin, Fazlul Karim Mamun, Md, Kabir, Nasima, Didar-ul-Alam, Md, Islam, Mohammed Mafizul, Chaity, Farjana Showline, Tijing, Leonard, Shon, Ho Kyong
• Format: Article
• Language: English
• Subjects: Acinetobacter seohaensis; Bangladesh; Cr (VI); Detoxification; Klebsiella quasivariicola; Staphylococcus saprophyticus; tannery waste
• ISSN: 1944-3986
• DOI: 10.1016/j.dwt.2024.100861

This paper investigated the Cr (VI) detoxification potential of 4 novel bacterial strains isolated from a long-term tannery waste-contaminated soil. Molecular techniques were used to identify the bacterial strains using 16 S rDNA gene sequencing. The Cr (VI) detoxification capacity of the bacteria was determined by 1,5-diphenylcarbazide (DPC) methods. The identified bacterial strains were Bacillus subterraneus MMKT-10, Klebsiella quasivariicola MMKT-15, Acinetobacter seohaensis MMKT-19, and Staphylococcus saprophyticus MMKT-25. All the strains showed maximum tolerance concentration (MTC) of Cr (VI) up to 4000 mg/L. However, in terms of Cr(VI) reduction rate, K. quasivariicola can be considered the most efficient, reducing the two preliminary Cr(VI) concentrations (10 and 20 mg/L) at 15 and 18 h, respectively, while the rest of the strains needed 30 h to reduce the same concentrations from the culture medium. The favorable temperature for Cr(VI) detoxification ranged from 30–40 °C. However, 100 % Cr (VI) reduction was achieved by all the strains at 35 0C. Interestingly, all the bacterial strains reduced a significant amount of Cr (VI) at 50 0C, indicative of their thermotolerant nature. The ideal pH for Cr (VI) reduction was 7 for B. subterraneus MMKT-10 and K. quasivariicola MMKT-15, whereas it was 8 for Acinetobacter seohaensis MMKT-19 and Staphylococcus saprophyticus MMKT-25. The indigenous bacterial strains isolated in this study could be one of the promising candidates for the detoxification of Cr (VI) contaminated sites. •Four novel Cr (VI) detoxifying bacteria have been characterized.•The maximum tolerance concentration varies up to 4000 mg/L.•Klebsiella quasivariicola MMKT-15 was best in terms of reduction rate.•100 % Cr (VI) reduction was achieved by all the strains at 35 0C.•The optimal pH for Cr (VI) detoxification was achieved at 7-8.