Enhanced Production of Polysaccharides and Protein Content in Cyanobacterium, Oscillatoria limnetica as a Defense Mechanism Against Low pH and Pb2+

Abstract

Living biomass has better ability to remove Pb2+ from wastewaters as compare to dead biomass. But, living biomass also have some practical limitations, such as, they are not efficient at low pH, and at high concentrations of metal ions. In the present study living biomass of Oscillatoria limnetica was assessed for its metal sorption capacity. O. limnetica considerably sorbed a large amount of Pb2+ within pH range 3-7. The maximum Pb2+ sorption capacity of O. limnetica was 434.78 mg/g. As photochemical efficiency data depicted, Pb2+ exerted inhibitory effects on photosynthesis of the test cyanobacterium. However, the test cyanobacterium showed considerable tolerance to Pb2+ exposure as concentration increased from 0 to 5 mg /L. Defense mechanisms of O. limnetica under Pb2+ enriched condition is probably associated with greater accumulation of intracellular polysaccharides (IPS) and protein. Nonetheless, since Pb2+ binding capacity of O. limnetica is significantly high than that of several other biosorbents, it can be considered as a promising biomaterial for removal of Pb2+ from wastewaters.