Effects of Cr(III) organic compounds on Lactobacillus plantarum

Abstract

Biotransformation of Cr(VI) to less toxic Cr(III) has been known to produce insoluble Cr(III) compounds and soluble Cr(III) organic complexes. However, recent research reports have indicated that Cr(III) organic complexes are relatively stable in the environment. Little has been reported on the fate and toxic effects of Cr(III) organic compounds on organisms. In this study, the toxic effects of the soluble Cr(III) organic complexes [Cr(III) citrate, Cr(III) histidine, Cr(III) lactate and Cr(III) glutamate] to a local strain of Lactobacillus plantarum isolated from sauerkraut was investigated. Growth inhibition, viable cell count and lactic acid inhibition were measured to determine the toxicity potential of the test compounds. The EC₅₀ values of Cr(III) citrate, Cr(III) histidine, Cr(III) lactate, and Cr(III) glutamate, calculated from the percent growth inhibition were found to be 56 mg L⁻¹, 70 mg L⁻¹, 81 mg L⁻¹, and 85 mg L⁻¹, respectively. Similar trend was observed in the viable cell counts and lactic acid production. Cr(VI) was observed to be more toxic than the Cr(III) organic compounds, while inorganic Cr(III) was the least toxic. The severity seemed to increase with increase in chromium compounds’ concentration. The results showed that Cr(III) citrate was the most toxic Cr(III) organic compound, while Cr(III) glutamate was the least.

Keywords:

• Cr(III) organic compounds
• toxicity
• Lactobacillus plantarum
• EC₅₀

Acknowledgments

This research work was supported by the National High Technology Research and Development Programme (863 programme No. 2007AA06Z337). T.W. Mutisya would wish to express his appreciation to the Chinese Scholarship Council and the Ministry of Livestock Development, Kenya for awarding the research fellowship.