Removal of Lead and Inhibition of Algal Growth Using Prodigiosin Produced by Serratia marcescens

Abstract

ABSTRACT

Background Heavy metals, especially lead, mercury and cadmium, are important environmental contaminants that present a greater danger to the ecosystem. Some species of toxic phytoplanktons grow rapidly in seawater leading to a phenomenon called the harmful algal bloom (HAB), which results in massive economic loss and environmental disturbances (White et al., 2007). In an effort to develop short-term solutions for controlling HABs and heavy metal contamination, several approaches are being explored, including chemical methods and recently biological methods (Jeong et al., 2005).This study examined the removal of lead and inhibition of Anabaena sphaerica and Oscillatoria agardhii growth using prodigiosin produced by Serratia marcescens.

Methodology Serratia marcescens,Anabaena sphaerica and Oscillatoria agardhii were obtained from Department of Microbiology, Federal University of Technology Minna, Nigeria. Inhibition of algal growth was studied by the addition of different concentrations of prodigiosin (50µl, 100µl, 150µl) in 90ml of algal culture in conical flask. Inhibition rates were determined using spectrophomotry at the interval of 72 hours of incubation. Removal of lead polluted soil sample was studied by the addition of different concentrations of prodigiosin (50µl, 100µl, 150µl) to 5g of lead polluted soil in 90ml of distilled water. Lead polluted soil was used for the experiment and the initial concentration was determined before treatment. The removal rate was determined at the interval of 4 weeks of incubation for six months using Atomic absorption spectroscopy (AAS).

Results Anabaena sphaerica recorded highest levels of inhibition (76.7%)at 100µg/L concentration of prodigiosin while Oscillatoria agardhiihad 66.3% at the same concentration. At concentration of 50µg/L, A. sphaerica recorded an inhibition rate of 66.3% whileO. Agardhii had 64.3% while at concentration of 150µg/L the inhibition rates were 67.2% and 66.5% respectively. The 100µl of prodigiosin immobilized 52.5% of lead after 20 weeks. This was followed by 50µL and 150µL of prodigiosin in which there was immobilization of 41.2% and 35.3% respectively. Discussion The results from this study revealed that prodigiosin has ability to inhibit A.sphaerica and O.agardhii growth. This is similar to the reports made by Jeong et al. (2005) and Jin et al. (2012), who used prodigiosin to treat Cochlodinium polykrikoides resulting in 78% inhibition. The removal of lead by the prodigioin may be due to the fact that prodigiosin binds to heavy metal to detoxify and remove the lead. The results suggest that the red pigment inhibited cyanobacteria growth and can be developed as a detoxifer of soil polluted with lead.

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