Abstrak: Satu bakteria penurun molibdenum dengan keupayaan baru untuk menyahwarna pewarna azo Kuning Metanil dilaporkan. Kondisi optimum untuk penurunan molibdenum adalah pada pH 6.3 dan pada suhu 34°C. Glukosa adalah penderma elektron yang terbaik. Keperluan-keperluan lain termasuklah kepekatan fosfat yang sempit di antara 2.5 dan 7.5 mM. Profil masa pengeluaran Mo-biru menunjukkan tempoh sela masa kira-kira 12 jam, jumlah maksimum Mo-biru dihasilkan pada kepekatan molibdat 20 mM dan pengeluaran maksimum pada masa 52 jam inkubasi. Logam-logam berat seperti merkuri, perak, tembaga dan kromium merencat penurunan sebanyak 91.9, 82.7, 45.5 dan 17.4%, masing-masing. Penyahwarnaan pewarna Kuning Metanil pada kepekatan 100 dan 150 mg/L berlaku pada hari ketiga dan hari enam inkubasi, masing-masing. Kepekatan yang lebih tinggi menghasilkan degradasi separa, dengan penyahwarnaan warna sebanyak 20% berlaku pada kepekatan 400 mg/L. Bakteria ini dikenal pasti secara separa berdasarkan analisis biokimia sebagai Bacillus sp. strain Neni-10. Spektrum penyerapan Mo-biru mencadangkan bahawa kompaun terhasil adalah fosfomolibdat terturun. Pengasingan bakteria ini, yang menunjukkan penurunan logam berat dan keupayaan penyahwarnaan pewarna, adalah diperlukan, terutamanya untuk bioremediasi.Kata kunci: Penurun Molibdenum, Molibdenum Biru, Bacillus sp., Pewarna Azo, Kuning Metanil Abstract: A molybdenum reducing bacterium with the novel ability to decolorise the azo dye Metanil Yellow is reported. Optimal conditions for molybdenum reduction were pH 6.3 and at 34°C. Glucose was the best electron donor. Another requirement includes a narrow phosphate concentration between 2.5 and 7.5 mM. A time profile of Mo-blue production shows a lag period of approximately 12 hours, a maximum amount of Mo-blue produced at a molybdate concentration of 20 mM, and a peak production at 52 h of incubation. The heavy metals mercury, silver, copper and chromium inhibited reduction by 91.9, 82.7, 45.5 and 17.4%, respectively. A complete decolourisation of the dye Metanil Yellow at 100 and * Corresponding author: yunus.upm@gmail.com Rusnam Mansor et al. 70150 mg/L occurred at day three and day six of incubations, respectively. Higher concentrations show partial degradation, with an approximately 20% decolourisation observed at 400 mg/L. The bacterium is partially identified based on biochemical analysis as Bacillus sp. strain Neni-10. The absorption spectrum of the Mo-blue suggested the compound is a reduced phosphomolybdate. The isolation of this bacterium, which shows heavy metal reduction and dye-decolorising ability, is sought after, particularly for bioremediation.
Heavy metals and organic xenobiotics including dyes are important industrial components with their usage amounting to the millions of tonnes yearly. Their presence in the environment is a serious pollution issue globally. Bioremediation of these pollutants using microbes with multiple detoxification capacity is constantly being sought. In this work we screen the ability of a molybdenum-reducing bacterium isolated from contaminated soil to decolorize various azo and triphenyl methane dyes. The bacterium reduces molybdate to molybdenum blue (Mo-blue) optimally at pH 6.0, and temperatures of between 25 and 40oC. Glucose was the best electron donor for supporting molybdate reduction followed by sucrose, trehalose, maltose, d-sorbitol, d-mannitol, d-mannose, myo-inositol, glycerol and salicin in descending order. Other requirements include a phosphate concentration of between 5.0 and 7.5 mM and a molybdate concentration between 10 and 20 mM. The absorption spectrum of the Mo-blue produced was similar to previous Mo-reducing bacterium, and closely resembles a reduced phosphomolybdate. Molybdenum reduction was inhibited by copper, silver and mercury at 2 ppm by 43.8%, 42.3% and 41.7%, respectively. We screen for the ability of the bacterium to decolorize various dyes. The bacterium was able to decolorize the dye Congo Red. Biochemical analysis resulted in a tentative identification of the bacterium as Serratia marcescens strain Neni-1. The ability of this bacterium to detoxify molybdenum and decolorize azo dye makes this bacterium an important tool for bioremediation.
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