Optimisation of Protein Recovery from Arthrospira platensis by Ultrasound-Assisted Isoelectric Solubilisation/Precipitation

A response surface methodology was used to optimise the solubilisation and precipitation of proteins from the cyanobacterium Arthrospira platensis. Two separate experiments were designed and conducted in a sequential manner. Protein solubilisation was affected by pH, extraction time, and biomass to solvent ratio (p < 0.001). Although spray-drying and the osmotic shock suffered when resuspending the dried biomass into distilled water led to a certain degree of cell wall disruption, the amount of protein that could be solubilised without an additional disruption step was in the range 30–60%. Sequential extractions improved protein solubilisation by less than 5%. For this reason, a pre-treatment based on sonication (400 W, 24 kHz, 2 min) had to be used, allowing the solubilisation of 96.2% of total proteins. Protein precipitation was affected by both pH and extraction time (p < 0.001). The optimised precipitation conditions, which were pH 3.89 over 45 min, led to a protein recovery of 75.2%. The protein content of the extract was close to 80%, which could be further increased by using different purification steps. The proteins extracted could be used in the food industry as technofunctional ingredients or as a source of bioactive hydrolysates and peptides for functional foods and nutraceuticals

Microalgae based wastewater treatment coupled to the production of high value agricultural products: Current needs and challenges

One of the main social and economic challenges of the 21st century will be to overcome the worlds’ water deficit expected by the end of this decade. Microalgae based wastewater treatment has been suggested as a strategy to recover nutrients from wastewater while simultaneously producing clean water. Consortia of microalgae and bacteria are responsible for recovering nutrients from wastewater. A better understanding of how environmental and operational conditions affect the composition of the microalgae-bacteria consortia would allow to maximise nutrient recoveries and biomass productivities. Most of the studies reported to date showed promising results, although up-scaling of these processes to reactors larger than 100 m2 is needed to better predict their industrial relevance. The main advantage of microalgae based wastewater treatment is that valuable biomass with unlimited applications is produced as a co-product. The aim of the current paper was to review microalgae based wastewater treatment processes focusing on strategies that allow increasing both biomass productivities and nutrient recoveries. Moreover, the benefits of microalgae based agricultural products were also discussed

Characterisation of the volatile profile of microalgae and cyanobacteria using solid-phase microextraction followed by gas chromatography coupled to mass spectrometry

[EN] Microalgae and microalgae-derived ingredients are one of the top trends in the food industry. However, consumers' acceptance and purchase intention of a product will be largely affected by odour and flavour. Surprisingly, the scientific literature present a very limited number of studies on the volatile composition of microalgae and cyanobacteria. In order to fill the gap, the main objective of the present study was to elucidate the volatile composition of seven microalgal and cyanobacterial strains from marine and freshwaters, with interest for the food industry while establishing its potential impact in odour. Among the seven selected strains, Arthrospira platensis showed the highest abundance and chemical diversity of volatile organic compounds (VOCs). Aldehydes, ketones, and alcohols were the families with the highest diversity of individual compounds, except in Arthrospira platensis and Scenedesmus almeriensis that showed a profile dominated by branched hydrocarbons. Marine strains presented a higher abundance of sulfur compounds than freshwater strains, while the ketones individual profile seemed to be more related to the taxonomical domain. The results of this study indicate that the VOCs composition is mainly driven by the individual strain although some volatile profile characteristics could be influenced by both environmental and taxonomical factors.This work was conducted in the framework of the SABANA Project funded by the EU H2020 Research and Innovation Programme (Grant agreement 727874), ALGALPROT Project funded by CEI·MAR (CEIJ-002) and financial support provided by the Basque Country Government (IT944-16)

Microalgae Derived Astaxanthin: Research and Consumer Trends and Industrial Use as Food

Astaxanthin is a high-value carotenoid currently being produced by chemical synthesis and by extraction from the biomass of the microalga Haematococcus pluvialis. Other microalgae, such as Chlorella zofingiensis, have the potential for being used as sources of astaxanthin. The differences between the synthetic and the microalgae derived astaxanthin are notorious: not only their production and price but also their uses and bioactivity. Microalgae derived astaxanthin is being used as a pigment in food and feed or aquafeed production and also in cosmetic and pharmaceutical products. Several health-promoting properties have been attributed to astaxanthin, and these were summarized in the current review paper. Most of these properties are attributed to the high antioxidant capacity of this molecule, much higher than that of other known natural compounds. The aim of this review is to consider the main challenges and opportunities of microalgae derived products, such as astaxanthin as food. Moreover, the current study includes a bibliometric analysis that summarizes the current research trends related to astaxanthin. Moreover, the potential utilization of microalgae other than H. pluvialis as sources of astaxanthin as well as the health-promoting properties of this valuable compound will be discussed

A novel photo-respirometry method to characterize consortia in microalgae-related wastewater treatment processes.

In this paper, a new photo-respirometry method for determining the rates of the main metabolic processes of microalgae-bacteria consortia in microalgae-based wastewater treatment processes has been developed and tested. The proposed protocol consists on applying dark and light periods to a microalgae-bacteria consortium in the presence of different substrates and measuring the rate of oxygen production. This allows determining the activity of microalgae, heterotrophic bacteria and nitrifying bacteria separately. The method has been optimized in terms of the operation strategy, including the starvation period required, the biomass concentration and the irradiance during the measurements. Results show that a starvation period of one to three days is necessary depending on the nutrient concentration. The optimal experimental conditions determined were a biomass concentration of 0.5 g/L and an irradiance of 200 μmol photons/m2·s. Furthermore, microalgae-bacteria samples from seven photobioreactors (indoor and outdoor) with different nutrient sources have been evaluated applying the methodology proposed. Regardless of the wastewater type, the microalgae activity is the main metabolic process, with heterotrophic activity increasing along with the chemical oxygen demand (COD) in the wastewater. Nitrifying activity was only observed when high ammonium concentrations were present. The developed method is a powerful tool to adequately manage and operate wastewater treatment processes using microalgae/bacteria consortia, providing valuable information to model wastewater treatment systems with microalgae and determine kinetic parameters

ABACO: A New Model of Microalgae-Bacteria Consortia for Biological Treatment of Wastewaters

Microalgae-bacteria consortia have been proposed as alternatives to conventional biological processes to treat different types of wastewaters, including animal slurry. In this work, a microalgae-bacteria consortia (ABACO) model for wastewater treatment is proposed, it being calibrated and validated using pig slurry. The model includes the most relevant features of microalgae, such as light dependence, endogenous respiration, and growth and nutrient consumption as a function of nutrient availability (especially inorganic carbon), in addition to the already reported features of heterotrophic and nitrifying bacteria. The interrelation between the different populations is also included in the model, in addition to the simultaneous release and consumption of the most relevant compounds, such as oxygen and carbon dioxide. The implementation of the model has been performed in MATLAB software; the calibration of model parameters was carried out using genetic algorithms. The ABACO model allows one to simulate the dynamics of different components in the system, and the relative proportions of microalgae, heterotrophic bacteria, and nitrifying bacteria. The percentage of each microbial population obtained with the model was confirmed by respirometric techniques. The proposed model is a powerful tool for the development of microalgae-related wastewater treatment processes, both to maximize the production of microalgal biomass and to optimize the wastewater treatment capacity

Role of Microalgae in the Recovery of Nutrients from Pig Manure

Animal production inevitably causes the emission of greenhouse gases and the generation of large amounts of slurry, both representing a serious environmental problem. Photosynthetic microorganisms such as microalgae and cyanobacteria have been proposed as alternative strategies to bioremediate agricultural waste while consuming carbon dioxide and producing valuable biomass. The current study assessed the potential of the microalga Scenedesmus sp. to remove nutrients from piggery wastewater (PWW) and the influence of the microalga on the microbial consortia. Maximum N-NH4+ consumption was 55.3 ± 3.7 mg·L−1·day−1 while P-PO43− removal rates were in the range 0.1–1.9 mg·L−1·day−1. N-NH4+ removal was partially caused by the action of nitrifying bacteria, which led to the production of N-NO3−. N-NO3− production values where lower when microalgae were more active. This work demonstrated that the photosynthetic activity of microalgae allows us to increase nutrient removal rates from PWW and to reduce the coliform bacterial load of the effluent, minimising both their environmental impact and health risks. Microalgae assimilated part of the N-NH4+ present in the media to produce biomass and did not to convert it into N-NO3− as in traditional processes

Potential of the cyanobacteria Anabaena sp. and Dolichospermum sp. for being produced using wastewater or pig slurry: Validation using pilot-scale raceway reactors

Indoor trials using 0.3 L bubble columns were conducted to demonstrate the potential of two cyanobacterial strains, Anabaena sp. and Dolichospermum sp., for being produced using nutrients obtained from waste streams (wastewater or pig slurry). Filtered pig slurry diluted at a concentration of 5% (v/v) led to a biomass productivity comparable to that of the standard medium (0.72 ± 0.05 and 0.66 ± 0.09 g·L-1·day-1 for Anabaena sp. and Dolichospermum sp. respectively). When produced using wastewater, the productivity was around 0.40 g·L-1·day-1 for both strains. The process was up-scaled using a 1.04 m3 raceway reactor located outdoors and operated at a culture depth of 0.12 m. Dilution rates of 0.1-0.3 day-1 were evaluated, achieving maximum biomass productivities when operating at a dilution rate of 0.3 day-1: 20.9 and 28.0 g·m-2·day-1 for Anabaena sp. and Dolichospermum sp., respectively. The maximum total nitrogen (N-NH4+ plus N-NO3-) removal rates for Anabaena sp. and Dolichospermum sp. were 2,471 and 3,621 mg·m-2·day-1, achieved when operating at a dilution rate of 0.3 day-1. Nitrification and stripping contributed to the N-NH4+ removal. When operating at 0.3 day-1, maximum P-PO43- removal rates for cultures of Anabaena sp. and Dolichospermum sp. were 81.5 and 87.1 mg·m-2·day-1. Illumina sequencing results revealed that both strains dominated the prokaryotic community of both cultures with other notable eukaryotic and prokaryotic genus detected including human pathogens. However, annual studies are needed to assess the potential of producing biomass rich in these strains outdoors

Year-long evaluation of microalgae production in wastewater using pilot-scale raceway photobioreactors: Assessment of biomass productivity and nutrient recovery capacity

The production of Scenedesmus sp. using wastewater was validated with pilot-scale raceway photobioreactors during a complete annual cycle in Almería (Spain). Three different dilution rates (0.1, 0.2, or 0.3 day-1) were evaluated. Biomass productivity was significantly affected by season (temperature and solar radiation) achieving a maximum value of 25.1 g·m-2·day-1 when operating at a dilution rate of 0.2 day-1 in summer. Up to 96% of the N-NH4+ present in the media was either assimilated by microalgae to produce biomass, converted to N-NO3+ by the action of nitrifying bacteria, or desorbed (stripping). Maximum nitrogen removal rates reached 4286.6 mg·m-2·day-1 in summer. In terms of P-PO43+, up to 75% was removed, with removal rates ranging from 147.5 mg·m-2·day-1 in winter to 227.2 mg·m-2·day-1 in summer. Data reported herein was used to validate the ABACO model, which demonstrated to be robust enough to accurately predict biomass productivity in pilot-scale outdoor open raceways throughout the year (R2=0.929; 0.05). The current study demonstrates the potential of raceway reactors and Scenedesmus sp. to recover nutrients from unprocessed wastewater with an exceptionally high content of N-NH4+ at pre-industrial scale. Keywords: Bioremediation, microalgae, biomass, photobioreacto