Isolation and Identification of Resistant Microorganisms from Automotive Paint Sludge

Background: Paint coating systems are widely implemented on different surfaces for both aspects of decoration and protection against corrosion. Due to the presence of organic compounds, the growth of microorganisms is more likely to take place in paints, such as automotive paint. In the process of automotive painting, 20% - 60% of the paint does not expose to the automotive body, which is washed using water and would lead to the painting sludge formation. Paint sludge is considered one of the hazardous wastes from the automotive industry, which is finally landfilled or incinerated. Objectives: Despite the presence of inhibiting compounds in paint sludge, such as heavy metals and biocides, the objective of this study was to isolate and identify microorganisms in the sludge culture. Methods: The microorganisms were isolated using serial dilutions, direct cultivation, and enrichment methods in basic salt cultivation media. Then, their biochemical and molecular specifications were investigated. Results: The number of microorganisms counted in paint sludge was approximately around 1 104 CFU/mL, and six isolatedcolonies were finally obtained. Conclusions: The main isolated microbial consortium from paint sludge included Pseudomonas aeruginosa, Staphylococcus haemolyticus, Micrococcus yunnanensis, Rothia amarae, Gordonia terrae, and Brevibacillus agri. Nearly 83% of the isolated strains were Gram-positive.