Microalgae biorefinery: proposition of a fractionation process

Le concept d’une algoraffinerie primaire traitant les principaux composants de microalgues (lipides, protéines, glucides et pigments) a été étudié. Une séquence d'opérations unitaires a été mis en œuvre afin d'obtenir des fractions enrichies de ces biomolécules tout en conservant leur integrité dans le procédé en aval. L'étude a été principalement centrée sur Chlorella vulgaris, une espèce connue pour sa paroi cellulaire rigide. La majorité de la fraction lipophile (lipides et pigments) a été récupérée en utilisant du dioxyde de carbone supercritique avec de l'éthanol en tant que co-solvant, sans opération unitaire de cassage cellulaire préalable. La fraction hydrophile (protéines et polysaccharides) a été récupérée dans la phase aqueuse après broyage à billes comme méthode de cassage cellulaire. Par la suite, la phase aqueuse a été séparée en trois fractions par un procédé d'ultrafiltration en deux étapes. Ainsi, les amidons, les pigments, les protéines et les sucres ont été séparés les uns des autres avec succès. Une analyse du cycle de vie sera nécessaire pour estimer le coût et la durabilité du procédé de fractionnement. ABSTRACT : A primary algorefinery, concept that deals with the main components of microalgae (lipids, proteins, carbohydrates and pigments), has been studied. A sequence of unit operations has been implemented in order to obtain separated enriched fractions of these biomolecules by conserving their integrity in the downstream process. The study was mainly centred on Chlorella vulgaris, a species known for its rigid cell wall. Most of the lipophilic fraction (lipids and pigments) was recovered using supercritical carbon dioxide with ethanol as a co-solvent, without a preliminary unit operation of cell disruption. The hydrophilic fraction (proteins and polysaccharides) was recovered in the aqueous phase after bed milling as cell disruption method. Subsequently, the aqueous phase was fractionated into three fractions by means of a process of two-stage ultrafiltration. Thus, starches, pigments, proteins and sugars were successfully separated from each other. A life cycle assessment will be necessary to estimate the cost and the sustainability of the fractionation process

Chemical Composition of the Essential Oil ofSatureja myrtifolia(Boiss. & Hohen.) from Lebanon

Satureja myrtifolia (Boiss. & Hohen.) Greuter & Burdeta medicinal plant belonging to the Lamiaceae family was collected from south of Lebanon and hydro-distilled by Clevenger method. Essential oil composition from aerial parts was analyzed by GC-MS technique. The odor of essential oil is characteristic, and clear yellow liquid oil was obtained after hydro-distillation. The yield of the essential oil was 1.25±0.02 % of dry matter (w/w). Thirty nine volatile components were identified in the Satureja myrtifolia oil, which shows a high amount of hydrocarbons class (57.82±0.1 %). Other classes were also identified such assesquiterpene hydrocarbons (12.96±0.1 %), oxygenated sesquiterpenes (10.65±0.2 %), phenolic compounds (10.32±0.1 %), acids (5.53±0.1 %), and monoterpenes hydrocarbons (2.21±0.1 %).In addition, a comparison with the unique study performed on Satureja myrtifolia was also carried out

Morphology, composition, production, processing and applications of Chlorella vulgaris: A review

Economic and technical problems related to the reduction of petroleum resources require the valorisation of renewable raw material. Recently, microalgae emerged as promising alternative feedstock that represents an enormous biodiversity with multiple benefits exceeding the potential of conventional agricultural feedstock. Thus, this comprehensive review article spots the light on one of the most interesting microalga Chlorella vulgaris. It assembles the history and a thorough description of its ultrastructure and composition according to growth conditions. The harvesting techniques are presented in relation to the novel algo-refinery concept, with their technological advancements and potential applications in the market

Evaluation of the protein quality of Porphyridium cruentum

The amino acid profile of the red microalga Porphyridium cruentum and its protein extract have been determined in order to assess the nutritional quality of this biomass for human consumption. Total protein determined by elemental analysis represented 56 % of its dry weight. Hydro-soluble proteins extracted at pH 12 and 40 °C were analysed by the Lowry method giving 47 %, which represented 84 % of total protein per dry weight. The amino acid sequence of the biomass and the protein extract was composed of a set of essential (39 % for the former and 37 % for the latter) and non-essential amino acids (61 % for the former and 63 % for the latter) that compares favourably with the standard protein/amino acid requirements proposed by Food and Agricultural Organisation and World Health Organisation

Selective and energy efficient extraction of functional proteins from microalgae for food applications

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Influence of microalgae cell wall characteristics on protein extractability and determination of nitrogen-to-protein conversion factors

Additional evidence about the influence of the cell wall physical and chemical characteristics on protein extractability was determined by calculating the conversion factors of five different microalgae known to have different cell wall composition, and their protein extracts. The conversion factors obtained for crude rigid cell walled Chlorella vulgaris, Nannochloropsis oculata and Haematococcus pluvialis were 6.35, 6.28 and 6.25, respectively, but for their protein extracts the values were lower with 5.96, 5.86 and 5.63. On the other hand, conversion factor obtained for fragile cell walled microalgae Porphyridium cruentum and Athrospira platensis was 6.35 for the former and 6.27 for the latter, with no significant difference for their protein extract with 6.34 for the former and 6.21 for the latter. In addition, the highest hydro-soluble protein percentage recovered from total protein was for P. cruentum 80.3 % and A. platensis 69.5 % but lower for C. vulgaris with 43.3 %, N. oculata with 33.3 % and H. pluvialis with 27.5 %. The study spotted the light on the influence of the cell wall on evaluating the conversion factor and protein extractability. In addition, it showed the necessity of finding the conversion factor every time accurate protein quantification is required, and proved that there is not a universal conversion factor that can be recommended

Techno-Functional Properties of Crude Extracts from the Green Microalga Tetraselmis suecica

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Aqueous extraction of proteins from microalgae: Effect of different cell disruption methods

The microalgal structure has been investigated to evaluate the release of proteins in aqueous media from five microalgae after conducting different cell disruption techniques: manual grinding, ultrasonication, alkaline treatment, and high-pressure treatment. After conducting cell disruption, the protein concentration in water was determined for all the microalgae and the results are discussed within the context of their cell wall structure. It was found that the aqueous media containing most protein concentration followed the order: high-pressure cell disruption>chemical treatment>ultrasonication>manual grinding. Fragile cell-walled microalgae were mostly attacked according to the following order: Haematococcus pluvialis<Nannochloropsis oculata<Chlorella vulgaris<Porphyridium cruentum≤Arthrospira platensis

Understanding the effect of cell disruption methods on the diffusion of Chlorella vulgaris proteins and pigments in the aqueous phase

Cell disruption of microalgae is usually evaluated by microscopic observations and quantification of the target molecules before and after cell disruption. The following study considers a new approach by analysing the diffusion behaviour of proteins and pigments of Chlorella vulgaris in an aqueous medium after applying different cell disruption methods. Results were revealed by microscopic observations, quantifying the concentration of the molecules of interest, and calculating their diffusion coefficient. Microscopic observations showed intact cells after applying chemical hydrolysis and ultrasonication. However, the majority of the cells lost their globular shape after bead milling and high-pressure homogenization. The protein concentration increased in the following order: ultrasonication bead milling > ultrasonication > high-pressure homogenization. Pigments were not detected in the aqueous phase of the chemical hydrolysis treatment, but their concentration and their diffusion were in the same order as proteins in the mechanical treatments. The study implied that diffusivity of the target molecules was not directly correlated to their increase concentration in the aqueous phase. Therefore, even if the cells were completely broken, diffusivity followed the hindered molecule diffusion phenomenon, which implies that somehow cells are not completely disrupted

Release of hydro-soluble microalgal proteins using mechanical and chemical treatments

In order to release proteins in the aqueous phase, high-pressure homogenization and alkaline treatments were applied to rupture the cell walls of five intensively grown microalgae. Protein characterisation was carried out by analysing the amino acid profiles of both the crude microalgae and the protein extracts, obtained after both types of treatment. The results showed that the proportion of proteins released from microalgae following both treatments was, in descending order: Porphyridium cruentum>Arthrospira platensis>Chlorella vulgaris>Nannochloropsis oculata>Haematococcus pluvialis, reflecting the increasingly protective, cell walls. Nonetheless, mechanical treatment released more proteins from all the microalgae compared to chemical treatment. The highest yield was for the fragile cell walled P. cruentum with 88% hydro-soluble proteins from total proteins, and the lowest from the rigid cell walled H. pluvialis with 41%. The proportion of essential and non-essential amino acids in the extract was assessed and compared to the crude microalgae profile. It was higher after alkaline treatment and much higher after high-pressure homogenization. These results suggest that non-essential amino acids are more concentrated actually inside the cells and that different types of proteins are being released by these two treatments