Effects of Different Culture Conditions and Growth States on the Structure and Hemostatic Properties of Coscinodiscus sp.

As a renewable marine inorganic material,Coscinodiscus sp.has significant potential in the field of rapid hemostasis.However,the low yield of Coscinodiscus sp.seriously limits the application.In this study,two new culture modes were adopted to increase the production of Coscinodiscus sp.,the effect of changes in culture conditions and growth status on the hemostatic activity of diatoms was detected.To prevent Coscinodiscus sp.from sinking in culture,the suspension culture mode was realized by adding0.5%agar.The semi-continuous high nutrient concentration culture mode increased the cell density of Coscinodiscus sp.to 11000cells mL^(-1)and shorten the culture cycle to 5 d.In terms of coagulation activity,the addition of frustules reduced the in vitro coagulation time by half and the activation time of coagulation by 70%.The hemolysis rate and cytotoxicity of frustules harvested in the two culture modes did not change significantly.The results showed that suspension culture mode and high nutrient concentration culture mode only changed the growth state of Coscinodiscus sp.,while the hemostatic performance remained stable.

Diatom and Diatomite: Different Focus on Natural Media to Material Science Path

Bio-silica issued from diatom, a microalgae, is attracted increasing attention in material science thanks to its peculiar nanoarchitecture and related properties with versatile applications. The present work is a deep analysis on morphological and chemical properties of bio-silica issued from fossil origin (diatomaceous earth) and living one (algal paste). An optimization in purification protocol was performed to obtain multiparous bio-silica from its raw media with keeping its original shape entirely. Multiple characterization methods as scanning electronic microscopy (SEM), infrared spectroscopy, x-ray diffraction (DRX), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption and inverse gas chromatography (IGC), were used to check the purification protocol efficiency as well as to gather accurate information on morphology and chemical composition of diatom material obtained in large amount.

Diatoms’ Breakthroughs in Biotechnology: <i>Phaeodactylum tricornutum</i>as a Model for Producing High-Added Value Molecules

With a world growing in population and nutritional needs, diatoms are considered nowadays as microalgae of a very important potential, thus they are exploited in several fields such as ecology, aquaculture, molecular farming, and pharma nutraceuticals. These coveted microalgae are characterized by their diversity, their high division rates, their complex life cycle, likewise their silicified cell walls named frustules. Thus, diatoms have been used for over a century after proving an efficient production of several molecules including Triacylglycerols (TAGs), H2, free fatty acids, vitamins, nutraceuticals, amino acids, proteins, terpenoids, alcohols and carbohydrates like starch, glycogen, and sucrose. Phaeodactylum tricornutum is the most promising diatom exploited to date, especially as a platform of pharmaceutical production. Herein, we expose diatoms’ main features that allowed using them for molecular farming. This review exposes likewise, the metabolism and the post-translational modifications (PTMs) of diatoms as well as current tools and challenges for their molecular and metabolic engineering for a more efficient production of valuable molecules. The knowledge on the biology of the diatoms, the molecular tools, and the various transformation methods available demonstrate the potential in biotechnology of these photosynthetic microorganisms. The widely studied P. tricornutum, as a model organism, is a promising diatom for production of valuable metabolites, despite the challenges and issues related to cultivation.

PHYTOPLANKTON,ESPECIALLY DIATOMS,IN THE GUT CONTENTS AND FECES OF TWO PLANTIVOROUS CYPRINIDS-SILVER CARP AND BIGHEAD CARP

In order to clarify whether the planktivorous silver carp and bighead carp can collect phytoplanktonas small as Cyclotella(【20μm)in Donghu Lake,studies on phytoplankton in their gut contents and feceswere made in 1990.The fish were cultured in both net cage in Donghu Lake and aquaria with the lakewater.Past the intestine,the average valve diameter of Cyclotella changed little.The average ratio of emptyfrustule of Cyclotella to total Cyclotella in the foregut contents of the fishes were 1.8—1.9 times higherthan that in the lake water,but changed little from foregut to feces.The aquarium experiment showedthat both carps could collect particles as small as 8-10μm, which was obviously narrower than the dis-tance between their gill rakers.Probably,secretion of mucus plays an important role in collecting suchsmall

Synthesis of Three-Dimensional Agaric-like Biomorphic TiO_2 by a Facile Method with Coscinodiscus sp.Frustule

The paper aims to expand the application of natural marine algae. Marine diatoms, which have intricate frustule struc- tures, can serve as bio-template for preparing three-dimensional materials. A simple and effective approach to synthesize the corru- gated agaric-like biomorphic TiO2 templated with frustule of Coscinodiscus sp. is reported. In the sol-gel preparation process, the titania-coating on the frustule is prepared through the deposition and condensation with the aid of acetylacetone （acac） as a control- ling agent to make the precursor Ti（BuO）4 hydrolyze slowly. The as-prepared titania-coated frustule and biomorphic TiOz is charac- terized by scanning electron microscopy （SEM） attached with energy dispersive X-ray spectrometer （EMAX） and X-ray diffraction （XRD）. The microstructure of the corresponding titania nanoparticles appears to be sphere with the diameters distributed around 10-20nm. The templating process is repeated for three cycles. Subsequently, the three-dimensional freestanding corrugated aga- ric-like biomorphic TiO2 structure is obtained by a selective removal in the NaOH solution. As far as we known, the 3D freestanding corrugated agaric-like biomorphic TiOz with greatly increased surface area is obtained for the first time.

Mechanical Simulation of a Diatom Frustule Structure

Diatoms possess intricately complicated nanopatterned silica outer shells, the so called frustules. Due to their excellent three-dimensional （3D） nanostructures, diatom frustules have attracted attentions from many fields to look for potential appli- cations, such as structural material design, light harvesting, photonics, molecular separation and bio-sensing. However, the mechanical property of frustule, especially the role of each single portion that structures a frustule, need to be clearly examined in order to provide a scientific support to frustule utilization. The reported work uses the Finite-Element （FE）-based simulation to investigate the relative mechanical properties of the frustule of the diatom Coscinodiscus sp. as compared with reference non-frustule structures. A three-dimensional model for the three featured layers of this frustule and a simplified model for its girdle band are built with the assistance of ABAQUS. A basic-cell concept is suggested; and the comparative results of several simulation groups are reported. The numerical results indicate that the seven-unit-cell model is able to catch the essential me- chanics of the Coscinodiscus sp. frustule under pressure and that the layered and porous structure of this frustule can effectively resist pressure.

Implications for photonic applications of diatom growth and frustule nanostructure changes in response to different light wavelengths

Diatoms are unicellular algae enclosed in intricate bio-silicified walls with repetitive nanostructures in a size range which makes them potentially relevant for a broad spectrum of industrial applications. How to optimize the nano-scale structures of the frustule for utilization of diatoms in nanotechnology is one of the technological challenges for these applications. Light is one of the most important abiotic factors for algal photosynthetic growth, and the frustule may play an important role in mediating light for these biological functions, as well as being central for its nano-technological applications. In this study we tested the influence of light quality on the nanostructure of the frustule of Coscinodiscus granii and compared this to growth rate response. The results showed that colored light （red, yellow, green and blue） at 300μmol photons m-2-s-1 resulted in a statistically significant change in nanostructure compared to white light. Green light at 100 μmol photon m-2.s-1 led to a significant decrease in mean frustule diameter and mean foramen diameter. Numerical simulations confirmed that the morphological changes obtained were sufficient to induce clear differences in the photonics properties of the frustule. The wavelength had no effect on the growth rate at high light intensity （300 μmol photons m-2.s-1）. However, at 100 μmol photons m-2.s-1, yellow, red-orange and green light resulted in significantly lower maximum growth rates than the other wavelengths. This response of the frustule structure to different light treatment indicates the possibility of a light-based frustule nanostructure manipulation method, which is simple and environmentally friendly.