Development of a novel biotoxicity screening assay for analytical use

A new biotoxicity assay has been developed and employed as an analytical screening tool. The proposed biotoxicity assay is simple and represents the first example of the use of Lactobacillus plantarum as a test micro-organism. The applicability of this method was demonstrated by evaluating the pollution of water due to the presence of several toxicants. Traditional parameters such as effective concentration (EC50) and lowest observed effect concentration (LOEC) provided by all the biotoxicity tests were employed in a screening method based on a binary toxic/non-toxic response. The threshold of the response was characterized by defining a mortality index (Im), which in this case was obtained by monitoring the consumption of glucose in the culture medium (Somogyi–Nelson method) or by turbidimetric measurements. Cut-off values established by the current legislation (or other preset values) were used as criteria to classify samples as positive or negative. Bacterial growth was inhibited by the presence of heavy metals such as mercury, cadmium, lead, copper and zinc. This methodology was applied to study the toxicity of heavy metals in different water samples.