Microbial evaluation and deterioration of paints and paint-products

The microbial quality of materials and final products of a reputable paint industry in Lagos area were analysed. The bacterial contaminants isolated in the paint-products included Bacillus brevis, B. polymyxa, B. laterosporus, Lactobacillus gasseri, L. brevis, Escherichia coli and Proteus mirabilis. The fungal contaminants detected in the paints were mainly Aspergillus niger, A. flavus and Penicillium citrinum. The microbial populations in the raw materials ranged from 1.0 x 10(6) - 9.5 x 10(6) cfu g(-1) for bacteria and between 1.25 x 10(4) and 6.8 x 10(4) cfu g(-1) for fungi while those present in packaging materials ranged from 3.45 x 10(6) - 7.65 x 10(6) cfu g(-1) for bacteria and 2.4 x 10(3) - 2.8 x 10(3) cfu g(-1) for fungi respectively. The bacterial populations in the fresh paint samples monitored every two weeks from the time of production ranged from 1.6 x 10(1) - 4.7 x 10(5) cfu ml(-1) while the fungal populations ranged from 1.0 x 10(1) - 5.5 x 10(3) cfu ml(-1) over a ten-month study period. The optical density at 600 nm increased while transmittance, pH, specific gravity and viscosity of the paint samples decreased over the period suggesting gradual deterioration of the aesthetic qualities of the paint-products with time as indicated by the measured parameters.