Light plays a crucial role in photosynthetic microalgae, and its quality is a key point for biomass production and the variability of the organisms’ biochemical composition, with blue and red, the light bands being the most effectively absorbed by green algae. Recently, light-emitting diodes (LEDs) have emerged as an alternative that allow a better modulation of algal metabolism. The aim of this work was to study the effects of blue and red LEDs on antioxidant capacity, biomass productivity (Px) and carotenoid and fatty acid content over time in a microalga known to be a producer of antioxidant compounds, Scenedesmus obliquus M2-1. Monochromatic blue (B) and red (R) LEDs and two dichromatic combinations of blue and red (BR (40:60) and BR (50:50)) were tested, and fluorescent lamp (FL) was used as a control. Then, supplementation effects of near-infrared radiation (NIR) LEDs were assessed in the same in parameters. Results show that B induced higher PX and higher content in fatty acids when compared with other LED conditions tested. Scenedesmus obliquus M2-1 under R attained a higher antioxidant capacity and under BR (40:60) a higher carotenoid production, particularly lutein and β-carotene, when compared with that of FL. NIR supplementation in BR (40:60) and R treatments enhanced PX and fatty acid content, changing the profile of antioxidant compound production over time, but keeping the maximum concentration. Additionally, NIR supplementation decreased the total carotenoid production. This study reveals that the use of R and BR (40:60) LEDs are a useful tool to enhance the production of carotenoids in S. obliquus M2-1.

Light-emitting diodes—a plus on microalgae biomass and high-value metabolite production

Nowadays, the progressive decrease of primary natural resources and ongoing upward trend in terms of energy demand, have resulted in development of new generation technological processes which are focused on step-wise production and residues utilization. Thus, microalgae-based 3rd generation bioeconomy is considered one of the most promising approaches that allow production of valueadded products and sophisticated utilization of residues biomass. In comparison to conventional biomass, microalgae can be cultivated in wide range of conditions without compromising food and feed production, and thus, addressing issues associated with negative social and environmental impacts. However, one of the most challenging tasks is to undergo seasonal variations and to achieve optimal growing conditions for indoor closed systems that can cover further demand for material and energetic utilization of microalgae. For instance, outdoor cultivation in St. Petersburg (Russia) is only suitable within rather narrow time frame (from mid-May to midSeptember). At earlier and later periods, insufficient sunlight and heat for the growth of microalgae were detected. On the other hand, without additional physical effects, the biomass increment in summer is 3-5 times per week, depending on the solar radiation and the ambient temperature. In order to increase biomass production, scientists from all over the world have proposed various technical solutions for cultivators and have been studying the influence of various physical factors affecting biomass growth namely: magnetic field, radiation impact, and electric field, etc. In this paper, the influence of infrared radiation (IR) and fluorescent light on the growth rate of microalgae Chlorella sorokiniana has been studied. The cultivation of Chlorella sorokiniana was carried out in 500 ml cylindrical glass vessels, which were constantly aerated. To accelerate the cultivation process, the mixture was stirred for 15 minutes at 500 rpm following 120 minutes of rest time. At the same time, the metabolic needs in nutrients were provided by the addition of microand macro-nutrients in the microalgae growing medium. Lighting was provided by fluorescent lamps with the intensity of 2500 ± 300 lx. The influence of IR was determined using IR lamps with a voltage of 220 V, power of 250 W, in order to achieve the intensity of 13 600 ± 500 lx. The obtained results show that under the influence of fluorescent lamps along with the combined effect of active aeration and variable mixing, the biomass increment on the 2nd day was three times, and on the 7th day, it was eight-fold. The growth rate of microalgae under the influence of IR radiation was lower and has reached 22.6ꞏ10 cellsꞏmL. However, application of IR lamps for the biomass growth allows maintaining the optimal temperature of microalgae suspension at approximately 25-28°C, which might especially be beneficial during the cold season in extreme climate zones. Natalia Politaeva is with Peter the Great St. Petersburg Polytechnic University, the Higher School of Biotechnology and Food Technology, St. Petersburg, Russia (e-mail: conata07@list.ru). Iuliia Smiatskaia and Iuliia Bazarnova are with Peter the Great St. Petersburg Polytechnic University, the Higher School of Biotechnology and Food Technology, St. Petersburg, Russia. Iryna Atamaniuk and Kerstin Kuchta are with Hamburg University of Technology, Institute for Environmental Technology and Energy Economics, Hamburg, Germany (e-mail: iryna.atamaniuk@tuhh.de, kuchta@tuhh.de). Keywords—Biomass, fluorescent lamp, infrared radiation, microalgae.

/pdf/influence-of-infrared-radiation-on-the-growth-rate-of-40ng9co80t.pdf

Influence of Infrared Radiation on the Growth Rate of Microalgae Chlorella sorokiniana

Over the last decade due to climate change and a strategy of natural resources preservation, the interest for the aquatic biomass has dramatically increased. Along with mitigation of the environmental pressure and connection of waste streams (including CO2 and heat emissions), microalgae bioeconomy can supply food, feed, as well as the pharmaceutical and power industry with number of value-added products. Furthermore, in comparison to conventional biomass, microalgae can be cultivated in wide range of conditions without compromising food and feed production, thus addressing issues associated with negative social and the environmental impacts. This paper presents the state-of-the art technology for microalgae bioeconomy from cultivation process to production of valuable components and by-streams. Microalgae Chlorella sorokiniana were cultivated in the pilot-scale innovation concept in Hamburg (Germany) using different systems such as race way pond (5000 L) and flat panel reactors (8 x 180 L). In order to achieve the optimum growth conditions along with suitable cellular composition for the further extraction of the value-added components, process parameters such as light intensity, temperature and pH are continuously being monitored. On the other hand, metabolic needs in nutrients were provided by addition of microand macro-nutrients into a medium to ensure autotrophic growth conditions of microalgae. The cultivation was further followed by downstream process and extraction of lipids, proteins and saccharides. Lipids extraction is conducted in repeated-batch semi-automatic mode using hot extraction method according to Randall. As solvents hexane and ethanol are used at different ratio of 9:1 and 1:9, respectively. Depending on cell disruption method along with solvents ratio, the total lipids content showed significant variations between 8.1% and 13.9 %. The highest percentage of extracted biomass was reached with a sample pretreated with microwave digestion using 90% of hexane and 10% of ethanol as solvents. Proteins content in microalgae was determined by two different methods, namely: Total Kejadahl Nitrogen (TKN), which further was converted to protein content, as well as Bradford method using Brilliant Blue G-250 dye. Obtained results, showed a good correlation between both methods with protein content being in the range of 39.8–47.1%. Characterization of neutral and acid saccharides from microalgae was conducted by phenol-sulfuric acid method at two wavelengths of 480 nm and 490 nm. The average concentration of neutral and acid saccharides under the optimal cultivation conditions was 19.5% and 26.1%, respectively.  Subsequently, biomass residues are used as substrate for anaerobic digestion on the laboratory-scale. The methane concentration, which was measured on the daily bases,

Case Study on Innovative Aquatic-Based Bioeconomy for Chlorella sorokiniana

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Influence of Infrared Radiation on the Growth Rate of Microalgae Chlorella sorokiniana

Case Study on Innovative Aquatic-Based Bioeconomy for Chlorella sorokiniana