Analytical speciation of chromium in in-vitro cultures of chromate-resistant filamentous fungi

Abstract

In this work, different analytical speciation schemes have been used to study the reduction of Cr(VI) by a chromate-resistant strain of filamentous fungi Ed8 (Aspergillus sp), indigenous to contaminated industrial wastes. As demonstrated previously, this strain has the capability to reduce chromate present in the growth medium without its accumulation in the biomass, yet the reduced chromium end-products have not been characterized. Liquid growth medium, initially containing 50 mg L(-1) Cr(VI), was analyzed for Cr(III)/Cr(VI) and for total Cr at different time intervals (0-24 h) after inoculation with fungi. Three hyphenated procedures, based on the Cr(III)-EDTA formation and species separation by anion-exchange or ion-pairing reversed-phase chromatography with ICP-MS or DAD detection were used. The results obtained for Cr(VI) in each case were consistent, demonstrating efficient reduction of chromate during 24 h of Ed8 growth. However, pre-column complexation with EDTA did not ensure complete recovery of the reduced forms of chromium in the above procedures. An alternative speciation scheme, based on extraction of Cr(VI)-benzyltributylammonium bromide (BTAB) ion pairs into chloroform and subsequent determination of residual chromium by ICP-MS has provided evidence on the effective conversion of chromate into reduced chromium species in the growth medium. The results indicate the feasibility of using Ed8 strain for chromate bioremediation purposes. Analytically it can be concluded that speciation of chromium in biological systems should not be limited to its two most common oxidation states, because the actual reduced chromium species are not converted quantitatively to Cr(III)-EDTA.

Hexavalent Chromium Removal by a Paecilomycessp. Fungal Strain Isolated from Environment

“…These observations indicated that in culture of the fungus a carbon source is required to provide the reducing power needed to decrease Cr (VI) in the growth medium. Our observations are like to the report of Acevedo Aguilar et al, Prasenjit and Sumathi [13, 24] with glucose like carbon source, and are different from the observations of Srivasta and Thakur [28] with Aspergillus sp, and Acinetobater sp, who observed how the main carbon source is the sodium acetate.…”

“…However, other yeasts such as Candida utilis [11] and Candida maltosa [12] showed partial ability to reduce Cr (VI) and also the capability to accumulate Cr in the biomass. Recent reports have also examined Cr (III) and Cr (VI) uptake and accumulation by different filamentous fungi [13, 14]. The present study reports the isolation and identification of a Paecilomyces sp.…”

Uptake and Reduction of Hexavalent Chromium by Aspergillus Niger and Aspergillus Parasiticus

“…Cr(VI) -resistant organisms are known to produce chromium reductase, which mediates the transfer of electrons from NAD(P)H to Cr(VI), converting it to Cr(III) [25,29,51]. The abilities of Aspergillus and Penicillium species to massively reduce Cr(VI) to Cr(III) have earlier been reported [26,[52][53][54][55].…”

Simultaneous analysis of Cr(III), Cr(VI), and chromium picolinate in foods using capillary electrophoresis‐inductively coupled plasma mass spectrometry

“…On the other hand, Cr(VI) is considered to be extremely toxic to organism since it has strong mutagenic and carcinogenic effects . Many researches have reported that Cr(VI) is harmful to organelle, protein, and nucleic acid , and the Cr(VI) exposure can cause allergies, eczema, stimulation, and respiratory disorders . Therefore, it is crucial to develop a sensitive and accurate analytical method for the quantification of different chromium species in foods and environment in order to ensure the human health.…”