The Challenge of Ecophysiological Biodiversity for Biotechnological Applications of Marine Microalgae

In this review, we aim to explore the potential of microalgal biodiversity and ecology for biotechnological use. A deeper exploration of the biodiversity richness and ecophysiological properties of microalgae is crucial for enhancing their use for applicative purposes. After describing the actual biotechnological use of microalgae, we consider the multiple faces of taxonomical, morphological, functional and ecophysiological biodiversity of these organisms, and investigate how these properties could better serve the biotechnological field. Lastly, we propose new approaches to enhancing microalgal growth, photosynthesis, and synthesis of valuable products used in biotechnological fields, mainly focusing on culture conditions, especially light manipulations and genetic modifications

Spectral radiation dependent photoprotective mechanism in the diatom Pseudo-nitzschia multistriata.

Phytoplankton, such as diatoms, experience great variations of photon flux density (PFD) and light spectrum along the marine water column. Diatoms have developed some rapidly-regulated photoprotective mechanisms, such as the xanthophyll cycle activation (XC) and the non-photochemical chlorophyll fluorescence quenching (NPQ), to protect themselves from photooxidative damages caused by excess PFD. In this study, we investigate the role of blue fluence rate in combination with red radiation in shaping photoacclimative and protective responses in the coastal diatom Pseudo-nitzschia multistriata. This diatom was acclimated to four spectral light conditions (blue, red, blue-red, blue-red-green), each of them provided with low and high PFD. Our results reveal that the increase in the XC pool size and the amplitude of NPQ is determined by the blue fluence rate experienced by cells, while cells require sensing red radiation to allow the development of these processes. Variations in the light spectrum and in the blue versus red radiation modulate either the photoprotective capacity, such as the activation of the diadinoxanthin-diatoxanthin xanthophyll cycle, the diadinoxanthin de-epoxidation rate and the capacity of non-photochemical quenching, or the pigment composition of this diatom. We propose that spectral composition of light has a key role on the ability of diatoms to finely balance light harvesting and photoprotective capacity

Computerized Casts for Orthodontic Purpose Using Powder-Free Intraoral Scanners: Accuracy, Execution Time, and Patient Feedback

Introduction. Intraoral scanners allow direct images of oral situation, with fewer steps than conventional impressions. The purpose of this study was to compare the accuracy of digital impressions, traditional impressions, and digitalization of full-arch gypsum models, to evaluate timing of different methods and finally to study perception of patients about conventional and digital impression techniques. Methods. Dental arches of fourteen patients were evaluated by alginate impression, titanium dioxide powder-free intraoral scanning (Trios, 3Shape), and digitalization obtained from gypsum models using the same scanner. Conventional and digital techniques were evaluated through measurements (lower and upper arch anteroposterior length, lower and upper intercanine distance, and lower and upper intermolar distance) with a caliber for analogic models and using a computer software for digital models (Ortho Analyzer, Great Lakes Orthodontics). In addition, chairside and processing times were recorded. Finally, each patient completed a VAS questionnaire to evaluate comfort. Statistical analyses were performed with ANOVA and Tukey tests for accuracy measurements and paired t-test for times and VAS scores. Significance was predetermined at P<0.05. Results. The measurements obtained with intraoral scanning, gypsum models after conventional impression, and digitalized gypsum models were not significantly different. Both chairside and processing times of digital scanning were shorter than the traditional method. VAS reporting patients comfort were significantly higher when evaluating digital impression. Conclusions. Intraoral scanners used for orthodontic applications provide useful data in clinical practice, comparable to conventional impression. This technology is more time efficient than traditional impression and comfortable for patients. Further evolution with more accurate and faster scanners could in future replace traditional impression methods

Role of nutrient concentrations and water movement on diatom's productivity in culture

Microalgal growth maximization is becoming a duty for enhancing the biotechnological fate of these photosynthetic microorganisms. This study, based on an extensive set of data, aims to revisit diatom's cultivation in laboratory with the objective to increase growth rate and biomass production. We investigated the growth ability and resource requirements of the coastal diatom Skeletonema marinoi Sarno &amp; Zingone grown in laboratory in the conventional f/2 medium with aeration and in two modified conditions: (i) the same medium with water movement inside and (ii) an enriched medium with the same water movement. Results revealed that, by doubling the concentration of phosphate, silicate, microelements and vitamins, growth rate was successfully enhanced, preventing phosphate or silicate limitation in the f/2 culture medium. Yet, irrespective of the media (f/2 or enriched one), water movement induced an increase of growth efficiency compared to aeration, affecting nutrients' requirement and consumption by diatoms. This study is an important step for enhancing diatom biomass production, reducing its cost, as required in the blue biotechnology context

Variations of photosynthetic pigments content.

<p>(A) Chlorophyll <i>a</i> (Chl <i>a</i>; pg cell^–1), (B) Fucoxanthin (Fuco; pg cell^–1), (C) β-carotene : Chl <i>a</i> ratio, (D) Chlorophyll <i>c</i>₂ : Chl <i>a</i> ratio and (E) Chlorophyll <i>c</i>₃ : Chl <i>a</i> ratio. B-L, BR-L, BRG-L, R-L are blue, blue-red, blue-red-green, and red low light conditions, respectively; B-H, BR-H, and BRG-H are blue, blue-red, blue-red-green high light conditions, respectively. Data represent mean ± SD (<i>n</i> = 21).</p

De-epoxidation state (DES = Dt/(Dd+Dt)) and non-photochemical quenching (NPQ).

<p>Time distribution of DES in (A) low and (B) high light. Time distribution of NPQ in low (C) and high light (D). B-L, BR-L, BRG-L, R-L are blue, blue-red, blue-red-green, and red low light conditions, respectively; B-H, BR-H, and BRG-H are blue, blue-red, blue-red-green high light conditions, respectively. Time is in hours after the start of the experiment. Data represent mean ± SD (<i>n</i> = 3).</p

Light condition characteristics, and photosynthetic and biochemical properties in <i>Pseudo-nitzschia multistriata</i> cells.

<p>Blue, green and red fluence rates (µmol photon m⁻² s⁻¹) measured at light peak and red : blue ratio values for the different light conditions. <i>a</i>*×10^–11, absorption coefficient (m² cell⁻¹); PUR×10^–6, photosynthetically usable radiation (µW cell^–1); _relETR_max×10^–6, (maximal relative rate of linear electron transport, nmol e⁻¹ s⁻¹ cell⁻¹), α×10^–9 (maximum light use efficiency, nmol e⁻¹ s⁻¹ cell⁻¹(µmol photon m⁻² s⁻¹)⁻¹), and E<i>k</i> (light intensity for reaching _relETR_max, µmol photon m⁻² s⁻¹); POC, particulate organic carbon (pg cell⁻¹); POC/PON, particulate organic carbon (POC) to particulate organic nitrogen (PON) ratio (pg/pg); Chl <i>a</i>/POC×10^–3, Chlorophyll <i>a</i> to POC ratio (pg/pg). Data represent mean and standard deviation. For <i>a</i>* and PUR, <i>n</i> = 3; For _relETR_max, α and E<i>k</i>, <i>n</i> = 6 (mean of the two days light peak measurements); For POC, PON, POC/PON and Chl <i>a</i>/POC, <i>n</i> = 21.</p

Growth curve of <i>Pseudo-nitzschia multistriata</i>.

<p>Growth under (A) low and (B) high light. B-L, BR-L, BRG-L, R-L are blue, blue-red, blue-red-green, and red low light conditions, respectively; B-H, BR-H, and BRG-H are blue, blue-red, blue-red-green high light conditions, respectively. Red high light prevented cell growth. Experiments were performed during the exponential phase on days 3 to 5 (B-L), 1 to 3 (R-L, BR-L, BRG-L, B-H) and 2 to 4 (BR-H, BRG-H). Data represent mean ± SD (<i>n</i> = 3).</p