Chronicle of Marine Diatom Culturing Techniques

Diatoms are regarded as useful neutral lipid sources, as liquid fuel precursors, as foods for marine culture of zooplankters, larval and post-larval shrimp, copepods, juvenile oysters and as micromachines in nanotechnology. Combining microscopic observation with in situ culturing has been useful in areas of taxonomy, ecology, biomonitoring, biotechnology, etc. This communication reviews various culturing techniques of marine diatoms with the relative merits.

Hygrothermal durability and failure modes of FRP for marine applications

This article deals with the durability of 2D woven mat carbon/polyester, glass/isopolyester, and gel-coated glass/isopolyester reinforced composites under hygrothermic conditions with regard to marine applications. The test coupons were exposed to 60 degrees C and 70 degrees C at 95% RH for a maximum duration of 100 h. The samples were periodically withdrawn and weighed for moisture absorption and tested for the degradation in the mechanical properties such as ultimate tensile strength, flexural strength, interlaminar shear strength, and Young's modulus and flexural modulus. Carbon/isopolyester-based specimens showed greater stability with respect to degradation in the mechanical properties than the glass/isopolyester/gel coat- and glass/isopolyester-based specimens. Glass/isopolyester exhibited the maximum moisture absorption, whereas the minimum moisture absorption was found in glass/isopolyester/gel coat. Diffusion coefficient (D) was found to be the highest for glass/isopolyester and the lowest for glass/isopolyester/gel coat, based on the Fick's law of diffusion. Diffusion coefficient increases with the increase in temperature for all the specimens. Microstructure study of fractured specimens was carried out using scanning electron microscope to compare matrix/fiber debonding and matrix-degradation of fiber-reinforced polymer composites.

Bioconvection in an anisotropic scattering suspension of phototactic algae

Phototaxis is a directed swimming response dependent upon the light intensity sensed by microorganisms. Positive phototaxis denotes motion directed towards the source of light and negative phototaxis is motion directed away from it. In this paper, we investigate the onset of bioconvection in a suspension of anisotropic scattering phototactic algae illuminated by collimated radiation at the top. The basic state of the system is defined by the zero fluid flow and the up and down swimming, caused by the positive and negative phototaxis, is balanced by the diffusion. A comprehensive numerical study of the linear stability is presented with particular emphasis on the forward scattering effect. The onset of bioconvection occurs either via a stationary mode or an oscillatory mode. The transition from a stationary mode to an oscillatory mode or vice versa has been observed as the anisotropic coefficient is varied for certain parameter values. (C) 2012 Elsevier Masson SAS. All rights reserved.

Treatment efficacy of algae-based sewage treatment plants

Lagoons have been traditionally used in India for decentralized treatment of domestic sewage. These are cost effective as they depend mainly on natural processes without any external energy inputs. This study focuses on the treatment efficiency of algae-based sewage treatment plant (STP) of 67.65 million liters per day (MLD) capacity considering the characteristics of domestic wastewater (sewage) and functioning of the treatment plant, while attempting to understand the role of algae in the treatment. STP performance was assessed by diurnal as well as periodic investigations of key water quality parameters and algal biota. STP with a residence time of 14.3 days perform moderately, which is evident from the removal of total chemical oxygen demand (COD) (60 %), filterable COD (50 %), total biochemical oxygen demand (BOD) (82 %), and filterable BOD (70 %) as sewage travels from the inlet to the outlet. Furthermore, nitrogen content showed sharp variations with total Kjeldahl nitrogen (TKN) removal of 36 %; ammonium N (NH4-N) removal efficiency of 18 %, nitrate (NO3-N) removal efficiency of 22 %, and nitrite (NO2-N) removal efficiency of 57.8 %. The predominant algae are euglenoides (in facultative lagoons) and chlorophycean members (maturation ponds). The drastic decrease of particulates and suspended matter highlights heterotrophy of euglenoides in removing particulates.

Anticancer Effects of Brominated Indole Alkaloid Eudistomin H from Marine Ascidian Eudistoma viride Against Cervical Cancer Cells (HeLa)

Marine invertebrates called ascidians are prolific producers of bioactive substances. The ascidian Eudistoma viride, distributed along the Southeast coast of India, was investigated for its in vitro cytotoxic activity against human cervical carcinoma (HeLa) cells by the MTT assay. The crude methanolic extract of E. viride, with an IC50 of 53 mu g/ml, was dose-dependently cytotoxic. It was more potent at 100 mu g/ml than cyclohexamide (1 mu g/ml), reducing cell viability to 9.2%. Among nine fractions separated by chromatography, ECF-8 exhibited prominent cytoxic activity at 10 mu g/ml. The HPLC fraction EHF-21 of ECF-8 was remarkably dose- and time-dependently cytotoxic, with 39.8% viable cells at 1 mu g/ml compared to 51% in cyclohexamide-treated cells at the same concentration; the IC50 was 0.49,mu g/ml. Hoechst staining of HeLa cells treated with EHF-2I at 0.5 mu g/ml revealed apoptotic events such an cell shrinkage, membrane blebbing, chromatin condensation and formation of apoptotic bodies. Cell size and granularity study showed changes in light scatter, indicating the characteristic feature of cells dying by apoptosis. The cell-cycle analysis of HeLa cells treated with fraction EHF-21 at 1 mu g/ml showed the marked arrest of cells in G(0)/G(1), S and G(2)/M phases and an increase in the sub G(0)/G(1) population indicated an increase in the apoptotic cell population. The statistical analysis of the sub-G(1) region showed a dose-dependent induction of apoptosis. DNA fragmentation was also observed in HeLa cells treated with EHF-21. The active EHF-2I fraction, a brominated indole alkaloid Eudistomin H, led to apoptotic death of HeLa cells.