Effects of blue, orange and white lights on growth, chlorophyll fluorescence, and phycocyanin production of Arthrospira platensis cultures

Nitrogen removal pathways in lake restoration using microalgal-bacterial granular sludge: Unraveling influence of organics and carbon to nitrogen ratio

This study investigated the performance of microalgal-bacterial granular sludge (MBGS) in the restoration of Qingling Lake and Huangjia Lake, focusing on nitrogen removal under varying water quality conditions. Significant color changes in MBGS and differences in granule characteristics were observed, with Qingling Lake demonstrating superior removal efficiencies for ammonia nitrogen, nitrate nitrogen, and total nitrogen compared to Huangjia Lake. Stoichiometric analysis revealed that when the chemical oxygen demand (COD) and carbon-to-nitrogen (C/N) ratios were less than 20 mg/L and 20, respectively, assimilatory nitrate reduction was positively correlated with both, whereas denitrification was negatively correlated. Gene function analysis showed that Qingling Lake had a more active microbial community supporting efficient nitrogen metabolism. The findings highlighted the enormous potential of MBGS in lake restoration, demonstrating its ability to adapt to different COD concentrations and C/N ratios by altering its nitrogen removal pathways.

A review of phycocyanin: Production, extraction, stability and food applications

This paper aims to review the production, extraction, stability and food application of phycocyanin. Currently, light source modulation and organic solvent cultivation of high biomass phycocyanin is an important research direction. The development of nitrogen oxygen balanced system-assisted culture environments to raise production will become a trend, the green and sustainable characteristics of which compensate for the drawbacks of the former. Microfiltration, ultrafiltration, and ultrasonic cell rupture technologies address the drawbacks of solvent extraction and achieve a significant increase in purity. Biorefining technology may become the trend to achieve the highest purity and efficiency in large-scale production of phycocyanin. For the stability of phycocyanin, the development of complexes is a trend, but it should consider the suitability of the materials complex with them for production as foodstuffs. Phycocyanin is mainly developed as a natural pigment, and the main point is the coloring power and stability of natural pigments.

Traditional and new trend strategies to enhance pigment contents in microalgae

Microalgae are a source of a wide variety of commodities, including particularly valuable pigments. The typical pigments present in microalgae are the chlorophylls, carotenoids, and phycobiliproteins. However, other types of pigments, of the family of water-soluble polyphenols, usually encountered in terrestrial plants, have been recently reported in microalgae. Among such microalgal polyphenols, many flavonoids have a yellowish hue, and are used as natural textile dyes. Besides being used as natural colorants, for example in the food or cosmetic industry, microalgal pigments also possess many bioactive properties, making them functional as nutraceutical or pharmaceutical agents. Each type of pigment, with its own chemical structure, fulfills particular biological functions. Considering both eukaryotes and prokaryotes, some species within the four most promising microalgae groups (Cyanobacteria, Rhodophyta, Chlorophyta and Heterokontophyta) are distinguished by their high contents of specific added-value pigments. To further enhance microalgae pigment contents during autotrophic cultivation, a review is made of the main related strategies adopted during the last decade, including light adjustments (quantity and quality, and the duration of the photoperiod cycle), and regard to mineral medium characteristics (salinity, nutrients concentrations, presence of inductive chemicals). In contrast to what is usually observed for growth-related pigments, accumulation of non-photosynthetic pigments (polyphenols and secondary carotenoids) requires particularly stressful conditions. Finally, pigment enrichment is also made possible with two new cutting-edge technologies, via the application of metallic nanoparticles or magnetic fields.

Exploring effective light spectral conversion techniques for enhanced production of Spirulina-derived blue pigment protein, c-phycocyanin

Spirulina is a promising feedstock for c-phycocyanin, a blue pigment-protein, commercially incorporated in many food products for its desirable bright blue attributes, exceptional bioavailability, and inherent therapeutic properties. Remarkably, enhancing c-phycocyanin synthesis in Spirulina would facilitate economic viability and sustainability at large-scale production, as the forecasted market value is $ 409.8 million by 2030. Notably, the lighting source plays a key role in enhancing c-phycocyanin in Spirulina, and thus, strategies to filter/concentrate the photons of respective wavelengths, influencing light spectra, are beneficial. Enveloping open raceway ponds and greenhouses by luminescent solar concentrators and light filtering sheets enables solar spectral conversion of the sunlight at desirable wavelengths, emerges as a promising strategy to enhance synthesis of c-phycocyanin in Spirulina. Nevertheless, the conduction of techno-economic assessments and evaluation of scalability at large-scale cultivation of Spirulina are essential for the real-time implementation of lighting strategies.

Comparative Analysis of Effect of Culture Conditions on Growth and C-Phycocyanin Production in Helical and Linear Spirulina

Spirulina (Arthrospira and Spirulina spp.) has always been characterized by the helical trichomes, despite the existence of linear forms. A great debate is now open on the morphological flexibility of Spirulina, but it seems that both trichome morphology and C-phycocyanin (C-PC) concentrations are influenced by the culture conditions.This work compared the effect of some key growth factors (medium pH as well as its carbon, potassium, and salt contents) on the growth and C-PC concentration of helical and linear Spirulina strains. Further, two-phase strategies, including light and nitrogen variation, were applied to increase the in vivo C-PC accumulation into the trichomes. Results showed that high pH induced trichomes elongation and improved growth but decreased C-PC content (+ 65 and + 43% vs. -83 and -49%, for helical and linear strains, respectively). Variations in carbon and salt concentrations negatively impacted growth and C-PC content, even if the linear strain was more robust against these fluctuations. It was also interesting to see that potassium increasing improved growth and C-PC content for both strains.The variation of light wavelength during the enrichment phase (in the two-phase strategy) improved by 50% C-PC accumulation in trichomes, especially after blue lighting for 96 h. Similar result was obtained after 48 h of nitrogen reduction, while its removal from the medium caused trichomes disintegration. The current work highlights the robustness of linear Spirulina strain and presents an efficient and scalable way to increase C-PC in vivo without affecting growth.

Role of Algal-derived Bioactive Compounds in Human Health

Algae is emerging as a bioresource with high biological potential. Various algal strains have been used in traditional medicines and human diets worldwide. They are a rich source of bioactive compounds like ascorbic acid, riboflavin, pantothenate, biotin, folic acid, nicotinic acid, phycocyanins, gamma-linolenic acid (GLA), adrenic acid (ARA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), etc. Beta-carotene, astaxanthin, and phycobiliproteins are different classes of pigments that are found in algae. They possess antioxidant, anti-inflammatory and anticancer properties. The sulfur-coated polysaccharides in algae have been used as an anticancer, antibacterial, and antiviral agent. Scientists have exploited algal-derived bioactive compounds for developing lead molecules against several diseases. Due to the surge in research on bioactive molecules from algae, industries have started showing interest in patenting for the large-scale production of bioactive compounds having applications in sectors like pharmaceuticals, food, and beverage. In the food industry, algae are used as a thickening, gelling, and stabilizing agent. Due to their gelling and thickening characteristics, the most valuable algae products are macroalgal polysaccharides such as agar, alginates, and carrageenan. The high protein, lipid, and nutrient content in microalgae makes it a superfood for aquaculture. The present review aims at describing various non-energy-based applications of algae in pharmaceuticals, food and beverage, cosmetics, and nutraceuticals. This review attempts to analyze information on algal-derived drugs that have shown better potential and reached clinical trials.

Optimal Laboratory Cultivation Conditions of Limnospira maxima for Large-Scale Production

Cultivating Limnospira maxima, renowned for its abundant proteins and valuable pigments, faces substantial challenges rooted in the limited understanding of its optimal growth parameters, associated high costs, and constraints in the procurement of traditional nitrogen sources, particularly NaNO3. To overcome these challenges, we conducted a comprehensive 4 × 3 factorial design study. Factors considered included white, red, blue, and yellow light spectra, along with nitrogen sources NaNO3 and KNO3, as well as a nitrogen-free control, for large-scale implementation. Optimal growth, measured by Optical Density, occurred with white and yellow light combined with KNO3 as the nitrogen source. These conditions also increased dry weight and Chl-a content. Cultures with nitrogen deprivation exhibited high values for these variables, attributed to carbon accumulation in response to nitrogen scarcity. Phycocyanin, a crucial pigment for nutrition and industry, reached its highest levels in cultures exposed to white light and supplemented with KNO3, with an impressive content of 384.11 g kg-1 of dry weight. These results highlight the efficacy and cost-efficiency of using a combination of white light and KNO3 for large-scale L. maxima cultivation. This strategy offers promising opportunities to address global food security challenges and enhance the production of industrially relevant pigments.

Enhancing the bio-prospective of microalgae by different light systems and photoperiods

Microalgae are a source of highly valuable bioactive metabolites and a high-potential feedstock for environmentally friendly and sustainable biofuel production. Recent research has shown that microalgae benefit the environment using less water than conventional crops while increasing oxygen production and lowering CO2 emissions. Microalgae are an excellent source of value-added compounds, such as proteins, pigments, lipids, and polysaccharides, as well as a high-potential feedstock for environmentally friendly and sustainable biofuel production. Various factors, such as nutrient concentration, temperature, light, pH, and cultivation method, effect the biomass cultivation and accumulation of high-value-added compounds in microalgae. Among the aforementioned factors, light is a key and essential factor for microalgae growth. Since photoautotrophic microalgae rely on light to absorb energy and transform it into chemical energy, light has a significant impact on algal growth. During micro-algal culture, spectral quality may be tailored to improve biomass composition for use in downstream bio-refineries and boost production. The light regime, which includes changes in intensity and photoperiod, has an impact on the growth and metabolic composition of microalgae. In this review, we investigate the effects of red, blue, and UV light wavelengths, different photoperiod, and different lighting systems on micro-algal growth and their valuable compounds. It also focuses on different micro-algal growth, photosynthesis systems, cultivation methods, and current market shares.

Valuable pigments from microalgae: phycobiliproteins, primary carotenoids, and fucoxanthin

Phycobiliproteins, carotenoids and fucoxanthin are photosynthetic pigments extracted from microalgae and cyanobacteria with great potential biotechnological applications, as healthy food colorants and cosmetics. Phycocyanin possesses a brilliant blue color, with fluorescent properties making it useful as a reagent for immunological essays. The most important source of phycocyanin is the cyanobacterium Arthrospira platensis, however, recently, the Rhodophyta Galdieria sulphuraria has also been identified as such. The main obstacle to the commercialization of phycocyanin is represented by its chemical instability, strongly reducing its shelf-life. Moreover, the high level of purity needed for pharmaceutical applications requires several steps which increase both the production time and cost. Microalgae (Chlorella, Dunaliella, Nannochloropsis, Scenedesmus) produce several light harvesting carotenoids, and are able to manage with oxidative stress, due to their free radical scavenging properties, which makes them suitable for use as source of natural antioxidants. Many studies focused on the selection of the most promising strains producing valuable carotenoids and on their extraction and purification. Among carotenoids produced by marine microalgae, fucoxanthin is the most abundant, representing more than 10% of total carotenoids. Despite the abundance and diversity of fucoxanthin producing microalgae only a few species have been studied for commercial production, the most relevant being Phaeodactylum tricornutum. Due to its antioxidant activity, fucoxanthin can bring various potential benefits to the prevention and treatment of lifestyle-related diseases. In this review, we update the main results achieved in the production, extraction, purification, and commercialization of these important pigments, motivating the cultivation of microalgae as a source of natural pigments.

High Purity Grade Phycocyanin Recovery by Decupling Cell Lysis from the Pigment Extraction: an Innovative Approach

Phycocyanin, a phycobiliprotein, is one of the few natural blue pigments available as food colourant, and it is largely used in food industry. We have devised an innovative two-step extraction process which allowed to obtain bright blue phycocyanin crude extracts with high purity grade P (within 2.5 and 3.5) directly from fresh biomass of Arthrospira platensis Gomont 1892 (commonly named Spirulina). We found out and for the first time exploited ammonium sulphate capability to minimize the release of water soluble phycobiliproteins in aqueous medium during ultrasound-assisted cell lysis/purification phase. The conventional sequence which is, extraction followed by purification, was reversed. The extraction phase was decoupled from biomass cell lysis. Cell lysis, accomplished by ultrasonication in ammonium sulphate solution, was merged with purification in a single step, before the pigment extraction/recovering phase. The process was entirely carried out in aqueous solutions. No downstream purification was required to obtain products suitable for the most common phycocyanin applications (i.e. foods, nutraceuticals). Production time, hours instead of days, was reduced to the advantage of the product quality. The process has the great advantages of (1) direct use of extracting solutions that cannot be used in the ordinary ultrasound-assisted extraction of phycocyanin (because of the extensive simultaneous extraction of contaminant molecules), (2) gain of high commercial value phycocyanin due to the elevated purity grade and (3) direct production of highly concentrated bright blue pigment crude extracts (up to about 5 mg mL−1) immediately in hand to the market.

Graphical Abstract

The Assessment of the Real-Time Radiative Properties and Productivity of Limnospira platensis in Tubular Photobioreactors

The development of tools to predict the photobioreactors' (PBRs) productivity is a significant concern in biotechnology. To this end, it is required to know the light availability inside the cultivation unit and combine this information with a suitable kinetic expression that links the distribution of radiant energy with the cell growth rate. In a previous study, we presented and validated a methodology for assessing the radiative properties necessary to address the light distribution inside a PBR for varying illuminating conditions through the cultivation process of a phototrophic microorganism. Here, we sought to utilise this information to construct a predictive tool to estimate the productivity of an autotrophic bioprocess carried out in a 100 [L] tubular photobioreactor (TPBR). Firstly, the time-dependent optical properties over ten batch cultures of L. platensis were calculated. Secondly, the local volumetric rate of photon absorption was assessed based on a physical model of the interaction of the radiant energy with the suspended biomass, together with a Monte Carlo simulation algorithm. Lastly, a kinetic expression valid for low illumination conditions has been utilised to reproduce all the cultures' experimentally obtained dry weight biomass concentration values. Taken together, time-dependent radiative properties and the kinetic model produced a valuable tool for the study and scaling up of TPBRs.

Modeling and Optimizing the Effect of Light Color, Sodium Chloride and Glucose Concentration on Biomass Production and the Quality of Arthrospira platensis Using Response Surface Methodology (RSM)

Arthrospira platensis (Spirulina) biomass is a valuable source of sustainable proteins, and the basis for new food and feed products. State-of-the-art production of Spirulina biomass in open pond systems only allows limited control of essential process parameters, such as light color, salinity control, or mixotrophic growth, due to the high risk of contaminations. Closed photobioreactors offer a highly controllable system to optimize all process parameters affecting Spirulina biomass production (quantity) and biomass composition (quality). However, a comprehensive analysis of the impact of light color, salinity effects, and mixotrophic growth modes of Spirulina biomass production has not been performed yet. In this study, Response Surface Methodology (RSM) was employed to develop statistical models, and define optimal mixotrophic process conditions yielding maximum quantitative biomass productivity and high-quality biomass composition related to cellular protein and phycocyanin content. The individual and interaction effects of 0, 5, 15, and 30 g/L of sodium chloride (S), and 0, 1.5, 2, and 2.5 g/L of glucose (G) in three costume-made LED panels (L) where the dominant color was white (W), red (R), and yellow (Y) were investigated in a full factorial design. Spirulina was cultivated in 200 mL cell culture flasks in different treatments, and data were collected at the end of the log growth phase. The lack-of-fit test showed that the cubic model was the most suitable to predict the biomass concentration and protein content, and the two-factor interaction (2FI) was preferred to predict the cellular phycocyanin content (p > 0.05). The reduced models were produced by excluding insignificant terms (p > 0.05). The experimental validation of the RSM optimization showed that the highest biomass concentration (1.09, 1.08, and 0.85 g/L), with improved phycocyanin content of 82.27, 59.47, 107 mg/g, and protein content of 46.18, 39.76, 53.16%, was obtained under the process parameter configuration WL4.28S2.5G, RL10.63S1.33G, and YL1.00S0.88G, respectively.

Influence of Different Light Sources on the Biochemical Composition of Arthrospira spp. Grown in Model Systems

Arthrospira platensis and Arthrospira maxima are prokaryotic microalgae commercially marketed as spirulina. The pigments extracted from these algae are widely used for cosmetic and nutraceutical applications. This work aimed to evaluate the influence of three light-emitting lamps (white, orange and blue) on the growth and biomass composition of two strains of A. platensis (M2 and M2M) and one of A. maxima. The obtained data show strain- and light-dependent responses of the microalgae. In addition, white and orange lights led to a similar overall effect by increasing the levels of chlorophyll a and carotenoids. However, exposure to orange light resulted in the highest dry weight (5973.3 mg L−1 in M2M), whereas white light stimulated an increase in the carbohydrate fraction (up to 42.36 g 100 g−1 in A. maxima). Conversely, blue light led to a constant increase in the concentration of phycocyanin (14 g 100 g−1 in A. maxima) and a higher content of proteins in all strains. These results provide important environmental information for modulating the growth of different spirulina strains, which can be used to address the synthesis of biochemical compounds of strategic importance for the development of new nutraceutical foods.

Impact of streetlights on physiology, biochemistry and diversity of urban bryophyte: a case study on moss Semibarbula orientalis

The use of artificial light at night is a very basic symbol of urbanization and has distorted many ecological, biochemical and physiological phenomena in plants, which have settled for millions of years in the biological system. Continuous illumination of light significantly alters the circadian rhythm of all organisms. The present study was focused to understand the effects of continuous light (CL) on the biochemistry and physiology of moss Semibarbula orientalis. It was observed that H2O2 accumulation and activities of chlorophyllase, phenylalanine ammonia-lyase, superoxide dismutase and catalase enzymes significantly enhanced in plants growing under streetlights. Similarly, plants under CL showed a marked reduction in photosynthetic performance. Specific fluxes (ABS/RC, TR/RC, ET/RC), phenomenological fluxes (ABS/CS, TR/CS, ET/CS), density of photosystem-II, quantum yield of photosynthesis and chlorophyll concentration markedly declined in plants growing under streetlights. Depletion in performance indices (PIcs and PIabs) and primary and secondary photochemistry [PHIO/(1 − PHIO) and PSIO/(1 − PSIO)] were also noticed, which indicated failure of adaptive strategies of photosystem-II, resulting in the loss of biomass of S. orientalis. Biomass decline is also shown by a decrease in coverage, which reduces the bryophyte species richness of the chosen locations. Present studies clearly indicate that artificial light at night drastically affects the moss population. The reduction in the dominating species, S. orientalis, improves species evenness and results in a slow growth rate.