Chromium (VI) remediation by a native strain: effect of environmental conditions and removal mechanisms involved

Abstract

A native bacterial strain with high capability for Cr (VI) removal was isolated from tannery sediments located in Elena (Córdoba Province, Argentina). The strain was characterized by amplification of 16S rRNA gene and identified as Serratia sp. C8. It was able to efficiently remove different Cr (VI) concentrations in a wide range of pHs and temperatures. The addition of different carbon sources as well as initial inoculum concentration were analyzed, demonstrating that Serratia sp. C8 could reduce 80 % of 20 mg/L Cr (VI) in a medium containing glucose 1 g/L, at pH 6-7 and 28 °C as optimal conditions, using 5 % inoculum concentration. The mechanisms involved in Cr (VI) removal were also evaluated. The strain was capable of biosorpting around 7.5-8.5 % of 20 mg/L Cr on its cell surface and to reduce Cr (VI). In addition, approximately a 54 and 46 % of total Cr was detected in the biomass and in the culture medium, respectively, and in the culture medium, Cr (III) was the predominant species. In conclusion, Serratia sp. C8 removed Cr (VI) and the mechanisms involved in decreasing order of contribution were as follows: reduction catalyzed by intracellular enzymes, accumulation into the cells, and biosorption to the microbial biomass. This strain could be a suitable microorganism for Cr (VI) bioremediation of tannery sediments and effluents or even for other environments contaminated with Cr.

Exploration on the Cr(VI) resistance mechanism of a novel thermophilic Cr(VI)‐reducing bacteria Anoxybacillus flavithermusABF1 isolated from Tengchong geothermal region, China

“…Unspecific Cr(VI) resistant mechanism was mainly about anti‐oxidative stress including SOS repair system (Hu et al ., 2005) and ROS scavenging enzyme (Ramirez‐Diaz et al ., 2008; Hu et al ., 2021); Specific resistant mechanisms were focused on Cr(VI) selective biosorption (d'Abzac et al ., 2013; Sibi, 2016; Pradhan et al ., 2019) and bioreduction (Zhang and Li, 2011; Gonzalez et al ., 2014; Castro et al ., 2019). However, few studies were focused on the reduced uptake of Cr(VI).…”

Facilitating New Chromium Reducing Microbes to Enhance Hexavalent Chromium Reduction by In Situ Sonoporation-Mediated Gene Transfer in Soils

“…CRB-B1, 51 Bacillus cereus, 52 Bacillus methylotrophicus, 53 E. mexicanum CWB-54, 54 Pisolithus sp., 55,56 Serratia sp. C8, 57 and Sporosarcina saromensis M52. 58 Accordingly, some Cr-reductase genes (chrR, yieF, lpDh, and nemA) and Cr-resistant genes (chrB, chrC, chrA, and ruvB) have been well studied.…”

Cr(VI) Sorption from Aqueous Solution: A Review

“…This explanation is not convincing because, as discussed above, at pH 4 Cr(VI) is prevalently present as oxyanion. An alternative explanation might be the structural alteration of the sorbent surface in acidic environment and consequent loss of sorption capacity [33][34][35]. A third mechanism possibly contributing to reduce Cr(VI) sorption at low pH (<2) might be the formation of oligomers of chromium species such as Cr3O10 2− and Cr4O13 2− [36,37].…”

“…This explanation is not convincing because, as discussed above, at pH 4 Cr(VI) is prevalently present as oxyanion. An alternative explanation might be the structural alteration of the sorbent surface in acidic environment and consequent loss of sorption capacity [33][34][35] [24]. A pH rise from 5.9 to 8.1 remarkably reduced Cr(VI) removal.…”