Production of Microalgal Biomass at Different Growth Phases to Use as Biofuel Feedstock

The growth of microalgae under optimized conditions was determined for assessing their growth rate and biomass production. In this study, the growth of both green algae (Chlamydomonas noctigama and Chlorella vulgaris) and cyanobacteria (Anabaena variabilis and Nostoc spongiaeforme) was measured as optical density. Chlamydomonas noctigama and Chlorella vulgaris showed the doubling time of 9.5 and 8.0 hours, respectively, whereas Anabaena variabilis and Nostoc spongiaeforme showed the doubling time of 14.8 and 16.6 hours, respectively. All the species exhibited the highest growth in terms of biomass at the phase in between stationary and death phases. J. Asiat. Soc. Bangladesh, Sci. 47(2): 161-171, December 2021

Cross-Activation of Two Nitrogenase Gene Clusters by CnfR1 or CnfR2 in the Cyanobacterium Anabaena variabilis

Cyanobacterial nitrogen fixation is important in the global nitrogen cycle, in oceanic productivity, and in many plant and fungal symbioses. While the proteins that mediate nitrogen fixation have been well characterized, the regulation of this complex and expensive process is poorly understood in cyanobacteria.

Phytoremediation of Contaminated Water by Cadmium (Cd) Using Two Cyanobacteria Species (Anabaena Variabilis and Nostoc Muscorum)

Background: Water pollution with heavy metals is a severe dilemma that worries the whole world related to its risk to nature ecosystem and human being health. The main objective is to evaluate the removal efficiency of Cd with various concentrations from contaminated aqueous solution by two Cyanobacteria species (Nostoc muscorum and Anabaena variabilis). For this purpose, a designed laboratory pilot scale was applied using two cyanobacteria species (Nostoc muscorum and Anabaena variabilis), four different initial concentrations (0, 0.5, 1.0 and 2.0 mg L−1) for 21 days. Results: N. muscorum was more efficient than A. variabilis for removing Cd (II), because the optimum value of residual Cd achieved by N. muscorum after 21 days at (0.5 mg L-1) was (0.033 mg L-1), where the removal efficiency was 93.4%, while the residual Cd (II) by A. variabilis under the same conditions was (0.054 mg L-1), and the achieved removal efficiency was 89.13%. Algal growth parameters and Photosynthetic pigments were estimated for both Cyanobacteria species through the incubation period. Conclusions: High Cd concentration had a more toxic impact on algal growth. The outcomes of this study will help to produce treated water that could be reused in agrarian activities.

Influence of Nutrient Manipulation on Growth and Biochemical Constituent in Anabaena variabilis and Nostoc muscorum to Enhance Biodiesel Production

The present study aims to improve biomass and biochemical constituents, especially lipid production of Anabaena variabilis and Nostoc muscorum by formulating an optimal growth condition using various concentrations of nutrients (NO3−, PO43− and CO32−) for biodiesel production. The supplementation of the three nutrients by +50% showed the maximum dry weight and biomass productivity, while the macromolecule contents were varied. The depletion of N-NO3− by 50% N-NO3− showed the maximum lipid yield (146.67 mg L−1) in A. variabilis and the maximum carbohydrate contents (285.33 mg L−1) in N. muscorum with an increase of 35% and 30% over control of the synthetic medium, respectively. However, variation in P-PO43− and C-CO32− showed insignificant improving results for all biochemical compositions in both cyanobacteria. A. variabilis was the superior species for lipid and protein accumulation; however, N. muscorum showed the maximum carbohydrate content. Accordingly, A. variabilis was selected for biodiesel production. In A. variabilis, −50% N-NO3− resulted in 35% higher lipid productivity compared to the control. Furthermore, the fatty acid profile and biodiesel quality-related parameters have improved under this condition. This study has revealed the strategies to improve A. variabilis lipid productivity for biodiesel production for small-scale in vitro application in terms of fuel quality under low nitrate levels.

Biomedical potential of Anabaena variabilis NCCU-441 based Selenium nanoparticles and their comparison with commercial nanoparticles

Selenium nanoparticles (SeNPs) are gaining importance in the field of medicines due to their high surface area and unique properties than their other forms of selenium. In this study, biogenic selenium nanoparticles (B-SeNPs) were synthesized using cyanobacteria and their bioactivities (antioxidant, antimicrobial, anticancer and biocompatibility) were determined for comparison with commercially available chemically synthesized selenium nanoparticles (C-SeNPs). Color change of reaction mixture from sky blue to orange-red indicated the synthesis of biogenic SeNPs (B-SeNPs). UV–Vis spectra of the reaction mixture exhibited peak at 266 nm. During optimization, 30 °C of temperature, 24 h of time and 1:2 concentration ratio of sodium selenite and cell extract represented the best condition for SeNPs synthesis. Various functional groups and biochemical compounds present in the aqueous extract of Anabaena variabilis NCCU-441, which may have possibly influenced the reduction process of SeNPs were identified by FT-IR spectrum and GC–MS. The synthesized cyanobacterial SeNPs were orange red in color, spherical in shape, 10.8 nm in size and amorphous in nature. The B-SeNPs showed better anti-oxidant (DPPH, FRAP, SOR and ABTS assays), anti-microbial (antibacterial and antifungal) and anti-cancer activitities along with its biocompatibility in comparison to C-SeNPs suggesting higher probability of their biomedical application.

Bacterial Predation on Cyanobacteria

Predatory bacteria gained interest in the last 20 years. Nevertheless, only a few species are well characterized. The endobiotic predator <i>Bdellovibrio bacteriovorus</i> invades its prey to consume it from the inside, whereas <i>Myxococcus xanthus</i> hunts as a whole group to overcome its prey. Both species were described to prey on cyanobacteria as well. This minireview summarizes the findings of the last 20 years of predatory bacteria of cyanobacteria and is supplemented by new findings from a screening experiment for bacterial predators of the model organism <i>Anabaena variabilis</i> PCC 7937. Known predatory bacteria of cyanobacteria belong to the phyla Proteobacteria, Bacteroidetes, and Firmicutes and follow different hunting strategies. The underlying mechanisms are in most cases not known in much detail. Isolates from the screening experiment were clustered after predation behaviour and analyzed with respect to their size. The effect of predation in high nitrate levels and the occurrence of nitrogen-fixing cells, called heterocysts, are addressed.