Aerobic chromium(VI) reduction by chromium-resistant bacteria isolated from activated sludge

Abstract

A chromium-reducing strain isolated from activated sludge and subsequently identified as Clostridium sp. SS1 by a biomolecular method was studied for its resistance to toxic hexavalent chromium [Cr(VI)] and its ability to reduce Cr(IV). The strain was found to tolerate concentrations of Cr(VI) up to 50 mg/l; however, cell growth was severely affected by the presence of Cr(VI), especially at concentrations of more than 20 mg/l. Clostridium sp. SS1 also effectively reduced toxic Cr(VI) into the comparatively less toxic trivalent form. The optimum pH value for Cr(VI) reduction was 7.0, and the cells reduced Cr (VI) more efficiently at 30°C than at 20 and 40°C. Within the same incubation time, higher amounts of Cr(VI) were reduced at higher initial Cr(VI) concentrations (range 5-40 mg/l). Clostridium sp. SS1 had a higher volumetric [0.82 mg Cr(VI)/l/h] and greater capacity [72 mg Cr(VI)/g biomass] to reduce Cr(VI) at higher initial Cr(VI) concentrations (40 mg/l), suggesting that this strain could be potentially useful for the detoxification of Cr(VI) polluted sites.

Isolasi, Identifikasi, dan Uji Potensi Bakteri Laut sebagai Agen Bioremediasi Logam Berat Kromium (Cr)

“…PerkinElmer AAnalyst 600 pada panjang gelombang 357.9 nm (Singh et al, 2013). Setelah itu dilakukan pengukuran efisiensi reduksi konsentrasi kromium oleh bakteri dengan menggunakan Persamaan 2 (Nguema & Luo, 2012).…”

“…Berdasarkan kurva tersebut dapat diketahui bahwa penambahan kromium ke dalam media kultur dapat menghambat pertumbuhan ketiga isolat bakteri. Hasil yang sama diperoleh dari penelitian sebelumnya pada pertumbuhan Pseudomonas aeruginosa, Bacillus cereus, Ochrobactrum intermedium, Clostridium sp., Staphylococcus sp., Bacillus megaterium dan Bacillus circulans yang menunjukkan pertumbuhan bakteri yang semakin terhambat seiring dengan bertambah tingginya konsentrasi kromium dalam media kultur (Mistry et al, 2010;Munawaroh et al, 2017;Nguema & Luo, 2012;Rida et al, 2012;Singh et al, 2013;Srinath et al, 2002) (Priyadarshanee & Das, 2021).…”

“…Berdasarkan perkiraan asupan makanan harian yang aman dan memadai (Estimated Safe and Adequate Daily Dietary Intake / ESADDI) untuk kromium adalah 50-200 µg (Anderson, 1997). Namun, jika kromium dikonsumsi dalam jumlah konsentrasi yang tinggi maka dapat memberikan efek toksik, karsinogenik, dan teratogenik (Nguema & Luo, 2012). Kromium dapat menyebabkan kerusakan oksidatif bagi sel.…”

BACTERIAL Cr (VI) REDUCTION AND ITS IMPACT IN BIOREMEDIATION

“…(Desai et al, 2008), and Brucella sp. (Thacker et al, 2006), Clostridium sp (Nguema and Luo, 2012), Cellulomonas sp (Field et al, 2013), have been reported to reduce Cr(VI). Bacterial reduction of Cr(VI) can be considered as a mechanism of resistance to Cr(VI) (Ohtake et al, 1997).…”