Enhanced detection of heavy metals using Vibrio alginolyticus PBR1 by optimizing luminescence medium through statistical modeling

Abstract

The bioluminescent bacteria have been widely used for detecting toxic compounds present in aqueous systems where the light output declines due to the presence of toxic chemicals. In the present study, bioluminescent Vibrio alginolyticus PBR1 was used as a test organism. Optimum environmental conditions and amount of ingredients of luminescence medium were investigated to obtain maximum luminescence and growth by one-factor-at-a-time method and response surface methodology (RSM). The optimized environmental conditions such as incubation state, temperature and pH were found to be 120 rpm, 25 ℃ and 7.0 respectively. The RSM derived composition of optimized luminescence medium (g % w/v) was: NaCl, 1.22; yeast extract, 0.13 and peptone, 1.50. To measure the cytotoxic effect of heavy metals on PBR1, bioluminescence inhibition assay was carried out using optimized luminescence broth. The strain PBR1 showed highest sensitivity to chromium and lowest to arsenic with EC50 values of 9.06 mg L−1 and 34.43 mg L−1 respectively. The detection sensitivity was improved by using optimized luminescence medium since it comprised of less organic content that reduced the precipitation and complexation of heavy metals compared to other reported media with higher organic content. The study demonstrated that V. alginolyticus PBR1 can be used as a promising candidate for commercial toxicity testing kits for the detection and monitoring of toxic heavy metals.