The role of silver nanoparticles biosynthesized by Anabaena variabilis and Spirulina platensis cyanobacteria for malachite green removal from wastewater

In this study, biosynthesis of silver nanoparticles (AgNPs) using two species of cyanobacteria, Anabaena variabilis (Kütz) and Spirulina platensis (Gomont) was investigated and evaluated for dye removing capacity. The formation of AgNPs was detected by the change in colour using UV-Vis spectroscopy and further characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The obtained AgNPs were spherical to oval with average particle size of 17.9 and 26.4 nm for S. platensis and A. variabilis, respectively. These AgNPs were applied as bio-sorbent for the removal of malachite green (MG) dye released into wastewater. Within the tested initial concentration range of MG, the reaction exhibited first order kinetics model as monitored via UV spectroscopy. As the dye concentration decreased, the removal efficiency increased to reach 93% for S. platensis and 82% for A. variabilis AgNPs. The results also indicated that increased AgNPs concentration enhanced the MG removal with an efficiency up to 88% and 81% for S. platensis and A. variabilis AgNPs, respectively. The smaller particle diameter and larger specific surface area of S. platensis AgNPs enabled boosted catalytic activity for dye removal than those of A. variabilis. After the treatment with AgNPs, the resultant dye- AgNPs-free effluent proved non-toxic to Triticum aestivum L (Giza 171) seedlings, implying their safety for cultivation practices.

Cartap hydrochloride induced stress response in Anabaena variabilis ARM 441

Cartap hydrochloride is a moderately hazardous nereistoxin analogue insecticide that is predominantly applied in paddy fields of India, at a recommended dose of 10 μg ml^-1 to kill chewing and sucking insect pests of rice crop. Toxicity of cartap hydrochloride was studied on non-target free-living nitrogen fixing cyanobacterium Anabaena variabilis ARM 441 commonly used as algal biofertilizer in rice cultivation. Anabaena sp. could tolerate commercial grade insecticide up to 30 μg ml^-1. However, at the recommended dose of 10 μg ml^-1, it caused reduction in algal growth, total nitrogen and heterocyst frequency by 47.28, 24.29 and 17.72% respectively, as well as photosynthetic pigments under pure culture conditions. Scanning electron micrographs revealed cell rupture and breakage in filaments due to cartap exposure with the formation of akinetes. Cartap hydrochloride induced stress, since level of superoxide dismutase, peroxidase and catalase were increased by 108.57, 187.5 and 117% respectively. Generation of superoxide radicals and hydrogen peroxide were also increased by 152.48 and 34% respectively. Lipid peroxidation was increased by 31.03%, whereas there was decline in ascorbate content by 48.45%, however the glutathione content was increased by 128.57%. Increase in osmolytes such as proline from 8.6 to 32.8% and sucrose from 61.22 to 90.13% indicates their possible role in overcoming cartap induced oxidative stress and can be helpful in assessing its detrimental effect on Anabaena variabilis ARM 441, since cyanobacterial biofertilizers are purposely used in paddy fields as nitrogen contributors.

Toxic effects of bisphenol A and its analogues on cyanobacteria Anabaena variabilis and Microcystis aeruginosa

In the last decades, the use of bisphenol A has attracted global attention resulting from its actions as an endocrine disrupting compound. In this regard, various bisphenol analogues have been manufactured as a replacement for this compound in consumer products. As a result of the high production volumes, different bisphenol analogues are entered into the terrestrial and aquatic environment, which consequently leads to their increasing contamination and may pose serious risk to organisms. Nevertheless, only few studies have reported on the toxic effect of bisphenol analogues on phytoplankton. Therefore, in this study, the anticyanobacterial activity of six bisphenol analogues and their mixture were investigated for the first time. Bisphenol AF, bisphenol B and bisphenol C (14 d, EC₅₀ 12.88-54.87 mg L^-1) exhibit more toxic effect to both tested species in comparison to bisphenol A (14 d, EC₅₀ 55.27-78.96 mg L^-1). Moreover, data show that mixture of bisphenol analogues (14 d, EC₅₀ 32.32-60.88 mg L^-1) exhibit toxic effect similar to or even stronger than that of bisphenol A. The toxic effect of bisphenol analogues, singly and in combination on the growth of both cyanobacteria species was arranged in the following order: bisphenol AF > bisphenol C> bisphenol B> bisphenol A> bisphenol E> bisphenol BP and bisphenol B> bisphenol AF > bisphenol C> bisphenol A> bisphenol E> bisphenol BP for Anabaena variabilis and Microcystis aeruginosa, respectively. This research aims to assure a basic understanding of the toxic effects of bisphenol analogues on cyanobacteria and provides a more comprehensive view on environmental risk assessment.

Phycobiliproteins from Anabaena variabilis CCC421 and its production enhancement strategies using combinatory evolutionary algorithm approach

The production of phycobiliproteins (PBPs) from cyanobacteria represents both the industrial application and their commercial value. In this study, the capability of Anabaena variabilis CCC421 for the production of PBPs was evaluated which was further improved by optimization of selected BG-11 medium components viz. FAC, K₂HPO₄ and trace metals. A design matrix approach using evolutionary algorithm comprised of genetic-algorithm (GA) and fuzzy-logic-methodology (FLM), i.e., GA-Fuzzy, was used for the optimization. The maximum production of PBPs obtained with combinatory approach of GA-Fuzzy was 408.5 mg/L at an optimum combination of factors (FAC 0.153 g/L, K₂HPO₄ 0.2 g/L and Trace metals 0.5 ml/L) which was a 2.13 fold more than the control medium. This novel approach is very useful for modulating biological processes since various nutrients and metabolites have greater influence on these processes.