Spectroscopic investigation on the energy transfer process in photosynthetic apparatus of cyanobacteria

Fluorescence inner filters of Arthrospira platensis: Novel perspective for precise fluorescence-based sensors

Microalgae have been reputed as novel biological materials due to their unique structure, surface functionality and optical activity, making them worthwhile agents in biosensing and theranostic applications. However, further scrutiny is required for utilizing them in routine optical techniques due to their complex structure and diverse chemical components. Here, laser induced fluorescence (LIF) features of a bio-compatible microalgae i. e. Arthrospira platensis (Spirulina) have been assessed. Typical fluorescence properties as well as the inner filter effects (IFEs) were examined and revealed to be strongly dependent on concentration, excitation wavelength, and detection geometry as well. IFEs and resulting spectral shifts have been analyzed considering various SP chromophores, reabsorption processes, and resonance energy transfer (RET) mainly from "Carotenoids to Phycobilisomes" as well as "Phycobilisomes to Chlorophyll-a". As a result, LIF spectral shift due to the re-absorption events (secondary-IFE) is introduced as a credible parameter for design of precise fluorescence-based sensors, due to being less dependent on ambient noises. We hope that the findings provide novel features regarding the LIF of Spirulina (SP) that could be utilized to design and develop optical sensors in the field of photonics, material diagnosis and biomedical theranostics.

An integrated method for removal of harmful cyanobacterial blooms in eutrophic lakes

As the eutrophication of lakes becomes an increasingly widespread phenomenon, cyanobacterial blooms are occurring in many countries. Although some research has been reported, there is currently no good method for bloom removal. We propose here a new two-step integrated approach to resolve this problem. The first step is the inactivation of the cyanobacteria via the addition of H(2)O(2). We found 60 mg/L was the lowest effective dose for a cyanobacterial concentration corresponding to 100 μg/L chlorophyll-a. The second step is the flocculation and sedimentation of the inactivated cyanobacteria. We found the addition of lake sediment clay (2 g/L) plus polymeric ferric sulfate (20 mg/L) effectively deposited them on the lake bottom. Since algaecides and flocculants had been used separately in previous reports, we innovatively combined these two types of reagents to remove blooms from the lake surface and to improve the dissolved oxygen content of lake sediments.