Microbial Population Inhibition Method Through Spectrophotometry Absorption of Visible Light Applied to Ecotoxicological Analyses

Abstract

Ecotoxicology is a science that studies the effects of pollutants and forecast their transformations on the environment. Ecotoxicological studies have been used in soil and water quality assessment, development and implementation of new techniques of water and effluent treatment, tools for better industrial management, bioremediation techniques and sustainable agriculture approaches. Microorganisms, which were seen to detain a fundamental importance in nutrient cycling and energy flow, have been increasingly used as bioindicators in ecotoxicological analyses. The populational inhibition of microbiological strains may be measured through the absorbance of visible light, an efficient, fast, low-cost and reliable method that has been widely used in qualitative and quantitative analysis. In this manuscript, a real textile effluent sample was analyzed regarding its electric conductivity, pH, turbidity, solids, alkalinity, biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and a spectrophotometry microbial population inhibition (MPI) method using the Bacillus subtilis bacteria and the Saccharomyces cerevisiae yeast. The EC20, EC50 and acute toxicity indexes were satisfactory in relation to the widely used method of light reduction of the Vibrio fischeri luminescence bacteria. The MPI was shown to be a feasible method to determine the hazardous effects caused by the textile effluent sample towards the microbial populations.

Ecotoxicological response surface analysis of salt and pH in textile effluent on Bacillus subtilis and Lactuca sativa

“…Development rate of the B. subtilis bacteria. The DR of the B. subtilis was calculated according to Mainardi and Bidoia (2020), through the difference in absorbance of their cellular suspension (A600 nm) between tubes that contained the sample and tubes that did not contain the sample. The experiment was done, firstly, by cultivating the bacteria in 125 mL sterilized Erlenmeyer flasks that contained 50 mL of Nutrient Broth (Acumedia) for 12 h, under constant stirring at 220 r/min at 35°C.…”

“…Techniques that use microorganisms as bioindicators, which have enormous importance in ecosystems' nutrient cycling and energy flow, have been increasingly used in ecotoxicological analyses (Gu, 2019). Depending on the methodology, the use of microorganisms as ecotoxicological indicators is generally simple, rapid, requires a low sampling volume, and provides reproducible responses (Halmi, 2016; Mainardi and Bidoia, 2020). Additionally, the use of microorganisms does not typically face ethical concerns (Parvez et al, 2006).…”