Zn2+ sequestration by Nostoc muscorum: study of thermodynamics, equilibrium isotherms, and biosorption parameters for the metal.

Microbial biosorption has evolved as an effective strategy for heavy metal removal from contaminated waters. The common cyanobacterium Nostoc muscorum isolated from the banks of a polluted river in Meghalaya, India, was tested for its potential to remove Zn2+ from aqueous solutions. Energy-dispersive X-ray (EDX) study verified Zn binding on the cyanobacterial biomass, and FTIR analysis revealed many negatively charged functional groups (hydroxyl, carbonyl, alcohol, amine, phosphoryl, sulfhydryl, and carboxyl) on the cell surface that aided in metal binding. Thermodynamic studies established the biosorption process to be energetically favorable with negative free energy change (-10.404, -10.599, and -10.796 kJ/mol at 298, 303, and 308 K, respectively). Sorption isotherm data fitted best in the Langmuir isotherm indicating monolayer nature of Zn sorption. The organism showed hyper-accumulation tendency towards Zn with a maximum sorption capacity as high as 2500 mg of Zn taken up per gram of biomass. The separation factor R L calculated from Langmuir isotherm ranged between 0 and 1 signifying favorable interaction between the cyanobacterial biomass and the Zn ions. Various experimental parameters, viz. pH, temperature, inoculum age and size, and shaking rate, influenced Zn biosorption. Optimized experimental conditions significantly enhanced the sorption percentage. Sorption was primarily a fast surface phenomenon in the beginning with internalization of zinc ions by the live cells on prolonged exposure.

Cyanobacteria: A Precious Bio-resource in Agriculture, Ecosystem, and Environmental Sustainability.

Keeping in view, the challenges concerning agro-ecosystem and environment, the recent developments in biotechnology offers a more reliable approach to address the food security for future generations and also resolve the complex environmental problems. Several unique features of cyanobacteria such as oxygenic photosynthesis, high biomass yield, growth on non-arable lands and a wide variety of water sources (contaminated and polluted waters), generation of useful by-products and bio-fuels, enhancing the soil fertility and reducing green house gas emissions, have collectively offered these bio-agents as the precious bio-resource for sustainable development. Cyanobacterial biomass is the effective bio-fertilizer source to improve soil physico-chemical characteristics such as water-holding capacity and mineral nutrient status of the degraded lands. The unique characteristics of cyanobacteria include their ubiquity presence, short generation time and capability to fix the atmospheric N2. Similar to other prokaryotic bacteria, the cyanobacteria are increasingly applied as bio-inoculants for improving soil fertility and environmental quality. Genetically engineered cyanobacteria have been devised with the novel genes for the production of a number of bio-fuels such as bio-diesel, bio-hydrogen, bio-methane, synga, and therefore, open new avenues for the generation of bio-fuels in the economically sustainable manner. This review is an effort to enlist the valuable information about the qualities of cyanobacteria and their potential role in solving the agricultural and environmental problems for the future welfare of the planet.