Aerobic chromate reduction by chromium-resistant bacteria isolated from serpentine soil

Abstract

A group of 34 chromium-resistant bacteria were isolated from naturally occurring chromium percolated serpentine soil of Andaman (India). These isolates displayed different degrees of chromate reduction under aerobic conditions. One of the 34 isolates identified as Bacillus sphaericus was tolerant to 800 mgl(-1) Cr(VI) and reduced > 80% Cr(VI) during growth. In Vogel Bonner broth, B. sphaericus cells (10(10) cells ml(-1)) reduced 62% of 20mg l(-1) of Cr(VI) in 48h with concomitant discoloring of yellow medium to white one. Reduction of chromate was pronounced by the addition of glucose and yeast extract as electron donors. In the presence of 4.0 g l(-1) of glucose, 20mg l(-1) of Cr(VI) was reduced to 2.45mg l(-1) after 96h of incubation. Optimum pH and temperature for reduction were 6.0 and 25 degrees C, respectively. Increase in cell density and initial Cr(VI) concentration increased chromate reduction but was inhibited by metal ions like, Ni2+, Co2+, Cd2+ and Pb2+. Experiments with cell-free extracts indicated that the soluble fraction of the cell was responsible for aerobic reduction of Cr(VI) by this organism.

Remediation of chromium contaminants using bacteria

“…B. sphearicus from naturally occurring chromium percolated soil of Andaman Islands was tolerant to 15.4 mM Cr(VI) and reduced [80% of it during growth. Soluble fraction of the cell was responsible for aerobic reduction of chromate by this organism (Pal and Paul 2004). Burkholderia cepacia MCMB-821 isolated from the alkaline crater lake of Lonar was resistant to 19.2 mM Cr(VI) and reduced 98% of the 1.4 mM Cr(VI) within 36 h in the presence of 2% salt and lactose as the electron donor.…”

Hexavalent chromium reduction by immobilized cells of Bacillus sphaericus AND 303

“…Cr(VI) reduction by the immobilized cells have been used in different systems such as packed bed biofilm reactor, membrane bioreactor or column bioreactors operating under batch, continuous or stirred mode (Tucker et al1998;Pattanapipitpaisal et al 2001;Cordoba et al 2008). In our previous study, we have reported a Cr(VI)-resistant and reducing bacterium, Bacillus sphaericus AND 303 (MTCC 6512) from serpentine outcrops of Andaman, India and have also enumerated chromate reduction studies during the growth, with viable free whole cells and using cell-free extracts (Pal and Paul 2004;Pal et al 2005). The present study reports on the reduction of Cr(VI) by the immobilized cells of B. sphaericus AND 303 and influence of environmental conditions on chromate reduction.…”

“…The bacterium was previously isolated from serpentine outcrops of Andaman, India (Pal and Paul 2004). It was grown on slopes of Tryptic Soy Agar (Himedia, India) (containing casein hydrolysate 17.0 g; peptic digest of soyabean 3.0 g; NaCl 5.0 g and K 2 HPO 4 2.5 g in 1000 mL distilled water) at 32°C for 24 h and maintained with repeated sub-culturing at four weeks interval.…”

Isolation and identification of bacteria from rotary drum compost of water hyacinth

“…Additionally, a high count of actinomycetes, streptomycetes, bacteria and fungi was also observed throughout the whole period of compost formation of water hyacinth . Contaminated regions such as industrial waste, wastewater, soil, municipal waste and sewage sludge have been used as source of the isolation of the most robust microbes (Affan et al 2009;Bahig et al 2008;Bautista-Hernández et al 2012;Colak et al 2011;Congeevaram et al 2007;Pal and Paul 2004).…”