Axenic cyanobacterial (Nostoc muscorum) biofilm as a platform for Cd(II) sequestration from aqueous solutions

An environment friendly approach towards heavy metal remediation from water is the need of the hour. A novel approach to heavy metal bioremediation from water was attempted using axenic cultures of the photoautotrophic cyanobacterium, Nostoc muscorum immobilised on to glass surface through the formation of biofilms. Being a biofilm, it exhibited much higher cellular integrity than cell suspension cultures when exposed to high concentrations of cadmium, and could also withstand the harsh conditions prevalent in industrial effluents. Being a photosynthetic organism, culturing of N. muscorum as a biofilm was achieved with minimal requirements, such as water with minerals, light and stationary conditions, which also enabled ease of scalability. The strong adherence of the N. muscorum biofilm to the glass surface was beneficial as (i) no diffusion of cell mass on to the media was observed even with the use of top-end stirrer, (ii) no expensive separation techniques were required for separation of biomass from the treated solution, and (iii) direct contact of the solution containing metals to the active components on biofilm surface allowed better interaction. The N. muscorum biofilm exhibited the capability to sequester Cd(II) in the pH range 5–9, concentration range C=O and >C=N functional groups, and followed the Langmuir's adsorption isotherm. It is proposed to use the N. muscorum biofilm as a potential green technology for waste water treatment in future. •A novel approach to wastewater management: use of axenic Nostoc muscorum biofilms•Environment friendly, low cost and low waste approach: a step towards development of green technology•Tolerance to heavy metals and inherent toxicity of industrial effluents, ease of generation and scale up of Nm biofilms•Wide concentration (ppb-ppm) & pH range (5–9) and chemisorption of Cd(II) by Nm biofilm•Gives thrust to the area of wider usage of algal systems in wastewater management