Evaluation of cyanobacterial endolith Leptolyngbya sp. ISTCY101, for integrated wastewater treatment and biodiesel production: A toxicological perspective

Abstract

The present study evaluates the ability of an endolithic cyanobacterial strain to synergistically treat municipal wastewater and produce biomass. Leptolyngbya sp. ISTCY101 was cultivated in undiluted wastewater influent in batch mode and semi-continuous mode. A semicontinuous marble slab photobioreactor was designed to exploit the endolith's innate capability of developing biofilm and utilizing bicarbonate as source of inorganic carbon. Biomass productivities averaged to 85mgL−1d−1 and 2.93gm−2d−1 in batch mode and semi-continuous mode respectively. The endolith produced 25% (% w/dw) of lipids mainly consisting of saturated and monounsaturated (C16:0, C16:1, C18:0, C18:1) fatty acids (>65%). Maximum Nitrogen and Phosphorus removal rates of 4.37mgL−1d−1 and 1.01mgL−1d−1 were attained in semi-continuous mode. Post treatment analyses of wastewater via GC-MS and ICP-OES showed remarkable removal of major organic contaminants and trace metals respectively. Methyltetrazolium (MTT) assay for cytotoxicity and Comet assay for genotoxicity were carried out in human hepato-carcinoma cell line HepG2 to validate the treatment efficiency of the strain. A 2.3-fold reduction in MTT EC50 value and 10-fold reduction in olive tail moment after cyanobacterial treatment envisage its potential application in integrated wastewater treatment and biodiesel production.