Growth and biomass productivity of Scenedesmus vacuolatus on a twin layer system and a comparison with other types of cultivations

Potential of Porous Substrate Bioreactors for Removal of Pollutants from Wastewater Using Microalgae

Porous substrate bioreactors (PSBRs) are a new technology to grow microalgae immobilized in a dense culture and solve some problems linked to suspended cultivation. During recent years, this technology has been used in laboratory and pilot setups in different fields of environmental biotechnology, such as wastewater treatment. The aim of this short review is to introduce the PSBR technology, summarize the results obtained in removing some pollutants from wastewater, provide an assessment of the potential of PSBRs for wastewater treatment, and the subsequent use of the algal biomass for other purposes.

Anti-Dengue Activity of ZnO Nanoparticles of Crude Fucoidan from Brown Seaweed S.marginatum

Dengue fever is a rapidly spreading infection that affects people all over the tropics and subtropics, posing a significant public health threat. The brown seaweed Stoechospermum marginatum was found all over the world, from South Africa (Indian Ocean) to Australia (Pacific Ocean), among other places. In India, it is only available along the coast of the Bay of Bengal, which is a small region. Various metal oxides were proved to be successful in the formation of nanoparticles and zinc is one among them. In this present study, an attempt was made to study the anti-dengue activity of green synthesized zinc oxide nanoparticles of crude fucoidan isolated from brown seaweed S. marginatum. The fucoidan was isolated from the seaweed by acid extraction method and then characterized by UV, HPLC, and Fourier Transform Infra-Red (FT-IR) Spectroscopy. Then it was biosynthesized into ZnO nanoparticles and characterized by SEM-EDAX analysis. The results showed the formation of fucoidans and SEM studies showed the crystalline nature of the synthesized nanoparticles. The size of nanoparticles was in the range of 80-126 nm. The synthesized nanoparticles were tested with the C6/36 cell line and it was shown 99.09% of anti-dengue activity against the tested cell line. As an antiviral agent, the ZnO nanoparticles of fucoidans have been shown to be an excellent lead molecule for the treatment of dengue fever.

Evaluation of Growth Rate and Biomass Productivity of Scenedesmus quadricauda and Chlorella vulgaris under Different LED Wavelengths and Photoperiods

Cultivation has been identified as an essential stage for biofuel production. This research has examined two important parameters for the industrial production of microalgae, namely microalgae growth rate and biomass productivity. Chlorella vulgaris and Scenedesmusquadricauda were cultivated using a closed photobioreactor (PBR). A novel approach for cultivation and energy input reduction was developed by incorporating periods of darkness during cultivation, as would happen in nature. Three different LED light sources (white, red, and green) were used to determine the conditions that result in the highest growth rate and biomass productivity. C. vulgaris and S. quadricauda responded differently to lighting conditions. It was found that, depending on the LED source and light period, different growth rates and biomass productivities were obtained. Overall, experimental results obtained in this study indicated that a white LED is more effective than green or red LEDs in increasing microalgae growth rate and biomass productivity. A maximum growth rate of 3.41 d−1 and a biomass productivity of 2.369 g L−1d−1 were achieved for S.quadricauda under a 19 h period of white light alternating with 5 h of darkness. For C. vulgaris the maximum growth rate of 3.49 d−1 and maximum biomass productivity of 2.438 g L−1d−1 were achieved by continuous white light with no darkness period.

Using different cultivation strategies and methods for the production of microalgal biomass as a raw material for the generation of bioproducts

Microalgal biomass and its fine chemical production from microalgae have pioneered algal bioprocess technology with few limitations such as lab-to-industry. However, laboratory-scale transitions and industrial applications are hindered by a plethora of limitations comprising expensive in culturing methods. Therefore, to emphasize the profitable benefits, the algal culturing techniques appropriately employed for large-scale microalgal biomass yield necessitates intricate assessment to emphasize the profitable benefits. The present review holistically compiles the culturing strategies for improving microalgal biomass production based on appropriate factors like designing better bioreactor designs. On the other hand, synthetic biology approaches for abridging the effective industrial transition success explored recently. Prospects in synthetic biology for enhanced microalgal biomass production based on cultivation strategies and various mechanistic modes approach to enrich cost-effective and viable output are discussed. The State-of-the-art culturing techniques encompassing enhancement of photosynthetic activity, designing bioreactor design, and potential augmenting protocols for biomass yield employing indoor cultivation in both (Open and or/closed) methods are enumerated. Further, limitations hindering the microalgal bioproducts development are critically evaluated for improving culturing techniques for microalgal cell factories, subsequently escalating the cost-benefit ratio in bioproducts synthesis from microalgae. The comprehensive analysis could provide a rational and deeper detailed insight for microalgal entrepreneurs through alternative culturing technology viz., synthetic biology and genome engineering in an Industrial perspective arena.

Evaluation of Microalgae Antiviral Activity and Their Bioactive Compounds

During the last year, science has been focusing on the research of antivirally active compounds overall after the SARS-CoV-2 pandemic, which caused a great amount of deaths and the downfall of the economy in 2020. Photosynthetic organisms such as microalgae are known to be a reservoir of bioactive secondary metabolites; this feature, coupled with the possibility of achieving very high biomass levels without excessive energetic expenses, make microalgae worthy of attention in the search for new molecules with antiviral effects. In this work, the antiviral effects of microalgae against some common human or animal viruses were considered, focusing our attention on some possible effects against SARS-CoV-2. We summed up the data from the literature on microalgae antiviral compounds, from the most common ones, such as lectins, polysaccharides and photosynthetic pigments, to the less known ones, such as unidentified proteins. We have discussed the effects of a microalgae-based genetic engineering approach against some viral diseases. We have illustrated the potential antiviral benefits of a diet enriched in microalgae.

Comparison of Galdieria growth and photosynthetic activity in different culture systems

In the last years, the acidothermophilic red microalga Galdieria sulphuraria has been increasingly studied for industrial applications such as wastewater treatment, recovery of rare earth elements, production of phycobilins. However, even now it is not possible an industrial cultivation of this organism because biotechnological research on G. sulphuraria and allied species is relatively recent and fragmented. Having in mind a possible scale-up for commercial applications, we have compared the growth and photosynthetic performance of G. sulphuraria in four suspended systems (Inclined bubble column, Decanter Laboratory Flask, Tubular Bioreactor, Ultra-flat plate bioreactor) and one immobilized system (Twin Layer Sytem). The results showed that G. sulphuraria had the highest growth, productivity and photosynthetic performance, when grown on the immobilized system, which also offers some economics advantages.

Biomass and phycobiliprotein production of Galdieria sulphuraria, immobilized on a twin-layer porous substrate photobioreactor

The extremophile red alga Galdieria sulphuraria was successfully grown immobilized in a twin-layer porous substrate bioreactor (TL-PSBR). A maximal biomass growth rate of 10 g dry weight m^-2 day^-1 was measured at a photon fluence rate of 200 μmol photons m^-2 s^-1 with addition of 1% CO₂ and a temperature of 34 °C. Under these conditions, a maximal biomass value of 232 g m^-2 was attained after 33 days of growth. Phycobilin productivity, however, was highest at a lower photon fluence rate of 100 μmol photons m^-2 s^-1 and reached a phycobilin value of 14 g m^-2, a phycobilin content in the biomass of 63 mg g^-1 and a phycobilin growth rate of 0.28 g m^-2 day^-1 for phycocyanin and 0.23 g m^-2 day^-1 for allophycocyanin. Addition of CO₂ was essential to enhance growth and phycobilin production in G. sulphuraria and further optimization of the cultivation process in the TL-PSBR appears possible using a multi-phase approach, higher growth temperatures and optimization of nutrient supply. It is concluded that autotrophic cultivation of G. sulphuraria in a TL-PSBR is an attractive alternative to suspension cultivation for phycobilin production and applications in bioremediation.

Statistical optimization of light intensity and CO2 concentration for lipid production derived from attached cultivation of green microalga Ettlia sp

Attached cultivation systems have been receiving extensive attention as a breakthrough in microalgae cultivation technology. However, there is a lack of studies that emphasize precise optimization of important parameters in attached cultivation of microalgae. In this study, the effects of two major environmental parameters in photoautotrophic cultivation, light intensity and CO₂ concentration, on the biomass and lipid surface productivity of Ettlia sp. YC001 were optimized by employing Response Surface Methodology (RSM) and validated experimentally. The optimum initial conditions for attached cultivation were use of seed from the late exponential phase (LE) and an inoculum surface density of 2.5 g/m². By optimization, maximum biomass surface productivity of 28.0 ± 1.5 g/m²/day was achieved at 730 μE/m²/s with 8% CO₂. The maximum lipid surface productivity was 4.2 ± 0.3 g/m²/day at 500 μE/m²/s with 7% CO₂. Change of the fatty acid composition with respect to changes in environment parameters led to improvement of biodiesel quality at higher light intensity and higher CO₂ concentration. Attached cultivation of Ettlia sp. YC001 has successfully produced biomass and lipids at a high production rate with relatively low light energy demand and high CO₂ utilization.