Energy balance of algal biomass production in a 1-ha "Green Wall Panel" plant: How to produce algal biomass in a closed reactor achieving a high Net Energy Ratio

AbstractThe annual productivity of Tetraselmis suecica in a 1-ha Green Wall Panel-II (GWP-II) plant in Tuscany (Italy) is 36t (dry weight)ha−1year−1, which corresponds to an energy output of 799GJha−1year−1. The energy inputs necessary to attain that productivity amount to 1362GJha−1year−1, mainly given by the embodied energy of the reactor (about 30%), mixing (about 40%), fertilizers (11%) and harvesting (10%). The Net Energy Ratio (NER) of T. suecica production is thus 0.6. In a more suitable location (North Africa) productivity nearly doubles, reaching 66tha−1year−1, but the NER increases only by 40% and the gain (difference between output and inputs) remains negative. In a GWP-II integrated with photovoltaics (PV), the NER becomes 1.7 and the gain surpasses 600GJha−1year−1. Marine microalgae cultivation in a GWP plant, in a suitable location, can attain high biomass productivities and protein yields 30times higher than those achievable with traditional crops (soya). When the GWP reactor is integrated with PV, the process attains a positive energy balance, which substantially enhances its sustainability

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

The aim of this study was to evaluate the effects of different light colors on growth, pigment composition, and photosynthetic performance of Arthrospira platensis. Results showed that under orange light the biomass productivity increased due to the capability of A. platensis to fully absorb this portion of the light spectrum. Under blue light, phycocyanin increased continuously up to 13.2% ± 1.96 of dry weight at day 5, while under orange and white lights the phycocyanin content resulted lower, 7.1 ± 0.39 and 6.7% ± 1.58 of dry weight, respectively. Chlorophyll fluorescence measurements showed the maximum electron transport rate (rETRmax) in cells grown under orange light. The results of this study indicated that the orange light increased both growth and phycocyanin productivities, while blue light increased mostly the phycocyanin content, while biomass productivity was much lower. Further increase of phycocyanin content was observed shifting the light illuminating the cultures from orange to blue, attaining a raise in phycocyanin content from 8.6% to 12.5% of dry weight within 48 h from the start of the illumination with blue light. Within the same period of time no growth was observed indicating that the synthesis of phycocyanin can be decoupled from growth. This study provides useful physiological information regarding the effects of different light spectra on growth, phycocyanin, and photosynthetic performance, as a prerequisite to optimize the production of high value pigments from cultures of A. platensis

Effect of temperature on growth, photosynthesis and biochemical composition of Nannochloropsis oceanica, grown outdoors in tubular photobioreactors

Since temperature is an important factor affecting microalgal growth, photosynthetic rate and biomass composition, this study has accordingly focused on its effects on biomass yield and nighttime biomass loss, as well as photochemical changes, using Nannochloropsis oceanica as model species, grown in two outdoor 50-L tubular photobioreactors (PBR). In two independent trials, cultures were subjected to a diurnal light:dark cycle, under a constant temperature of 28 degrees C and, on the second trial, at 18 degrees C. Changes in culture performance were assessed by measuring growth, lipid and fatty acid composition of the biomass in both morning and evening. Our results revealed that N. oceanica shows a wide temperature tolerance with relevant nighttime biomass loss, that decreased at lower temperatures, at the expenses of its daily productivity. Fluorescence measurements revealed reversible damage to photosystem II in cells growing in the PBR under optimal thermal conditions, whereas microalgae grown at suboptimal ones exhibited an overall lower photosynthetic activity. Lipids were partially consumed overnight to support cell division and provide maintenance energy. Eicosapentaenoic acid (EPA) catabolism reached a maximum after the dark period, as opposed to their saturated counterparts; whereas lower temperatures led to higher EPA content which reached the maximum in the morning. These findings are relevant for the production of Nannochloropsis at industrial scale.European Cooperation in Science and Technology (COST) Action: European network for algal-bio-products (EUALGAE) [ES1408]Portuguese national funds from the Foundation for Science and Technology (FCT) [SFRH/BD/129952/2017]Laboratory for Process Engineering, Environment, Biotechnology and Energy -LEPABE -by the FCT/MCTES (PIDDAC) [UIDB/00511/2020]project: "LEPABE-2-ECO-INNOVATION" - North Portugal Regional Operational Program (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) [NORTE-01-0145-FEDER-000005]project: "DINOSSAUR" - ERDF through Programa Operacional Competitividade e Internacionalizacao (COMPETE2020) [PTDC/BBB-EBB/1374/2014-POCI-01-0145-FEDER-016640]project: "SABANA"- European Union [727874][UID/Multi/04326/2019]info:eu-repo/semantics/publishedVersio

Chemical composition and apparent digestibility of a panel of dried microalgae and cyanobacteria biomasses in rainbow trout (Oncorhynchus mykiss)

Despite a growing interest in microalgae and cyanobacteria as potential sources of nutrients in aquafeeds, little information is presently available on their nutritive value for carnivorous fish species. The aim of this study was to evaluate chemical composition and nutrient digestibility of a panel of microalgae and cyanobacteria dried biomasses (MACB), using rainbow trout (Oncorhynchus mykiss W.) as a fish model. Nine test diets were obtained by mixing 80 parts of a reference diet, added with 20 g/kg of acid insoluble ash as an indigestible marker, to 20 parts of each of the following dried whole-cell biomass: Arthrospira platensis, Nostoc sphaeroides, two strains of Chlorella sorokiniana, Nannochloropsis oceanica, Tisochrysis lutea, Phaeodactylum tricornutum, Porphyridium purpureum and Tetraselmis suecica. The digestibility measurements were conducted with rainbow trout (52.4 \ub1 1.5 g) kept in six tank units each including three 60-L vessels singularly stocked with 12 fish and fitted with a settling column for faecal recovery. Per each diet, faeces were collected over three independent 10-day periods. Apparent digestibility coefficients (ADCs) of dry matter, crude protein (CP), organic matter and gross energy (GE) of single MACB were calculated by difference relative to those of the reference diet. The MACBs had heterogeneous chemical composition (CP, from 20 to 69%; Lipid, 5\u201327%; GE, 12.5-\u201322.6 MJ/kg dry matter basis) reflecting their overall biodiversity. Most of them can be considered as virtually good sources of minerals and trace elements and exhibit an essential amino acid profile comparable or even better than that of soybean meal commonly used in fish feeds with P. purpureum showing the best protein profile. The digestibility results obtained with rainbow trout allowed ranking the MACBs into two major groups. A first one, including C. sorokiniana, N. oceanica and T. suecica, resulted in markedly lower (P < 0.05) crude protein and energy ADC (64\u201373%; 51\u201359%, respectively) compared to a second group including P. purpureum, T. lutea and cyanobacteria (CP-ADC, 83\u201388%; GE-ADC, 74\u201390%) while P. tricornutum resulted in intermediate values. Overall, the present study confirms the consistently reported role of cell-wall structure/composition in affecting accessibility of nutrients to digestive enzyme. Based on the overall outcomes, only T. lutea and cyanobacteria actually meet the requirements for being used as protein sources in aquafeeds provided their mass production becomes more feasible and costeffective, hence attractive for the feed-mill industry in the near future

Growth response, plasma metabolites and intestinal brush border enzyme activity of sea bass fed diets including a blend of two marine microalgae

Microalgae have attracted increasing attention as animal feed supplements since they are natural sources of bioactive compounds which give them nutraceutical properties in addition to their basic nutritional value. More recently, dry microalgae biomass have also been proposed as raw materials in partial substitution for fish meal and oil in aquafeeds. The aim of this study was to evaluate the effects of including a blend of dried marine microalgae in low fish meal/fish oil diets on growth performance, levels of plasma metabolites and activity of brush border intestinal enzymes in adult European sea bass (Dicentrarchus labrax, L.). Two test diets (A1 and A2) were prepared by including a blend of Isochrysis galbana and Tetraselmis suecica dried biomass in a 2:1 w:w ratio to replace 15 and 45% fish meal protein and 10 and 30% fish lipid of a control diet (C) with a 50:50 fish to vegetable-protein-lipid ratio. One hundred eight fish (mean body weight 204\ub112.7g) were randomly divided among 9 groups kept in a marine recirculating tank system ensuring nearly optimal water condition to sea bass (temperature 21\ub0C, salinity 28\u2030). Fish were fed the test diets to visual satiety over 15 weeks according to a randomized design with 3 replicates per dietary treatment. At the end of the trial, final biomass, specific growth rate (SGR) and feed conversion ratio (FCR) were calculated per group and 6 fish per dietary treatment were sacrificed and immediately subjected to blood and intestine sampling for further analysis of plasma metabolite levels (glucose, cholesterol, triglyceride, total proteins and albumin levels) and activity of brush border enzymes in different sections. No diet-induced effects were noted in the final individual live weight, 420\ub114.5g, SGR, 0.68\ub10.003 and FCR, 1.7\ub10.11. Amongst plasma metabolites, only cholesterol and total proteins were affected by dietary treatments resulting in reduced levels only in fish given the diet highest in microalgae relative to controls (347.2 vs 276.6 mg/dl and 5.90 vs 5.37 mg/dl; respectively, P<0.05). The activity of the intestinal mucosal enzymes varied according to the different intestinal tracts but did not show major diet-dependent changes. This study suggests that a blend of dried marine microalgae biomass could further reduce reliance on fish meal and fish oil in practical diets for adult sea bass without adversely affecting growth response and digestive-absorptive functions

Inclusion of the microalga Isochrysis aff. galbana in organic diets of European sea bass juveniles: effects on growth, feed utilisation and fillet composition

The interest towards several marine microalgal species as sustainable dietary sources alternative to fish meal /oil and able in maintaining fish performances and health benefits of their flesh consumption, has good grounds. In fact microalgae can represent a potential alternative ingredient to supplement the diet of high-value fish species or in organic-based aquaculture systems, due to their high content of good-quality protein, bio-active compounds, antioxidants, vitamins, minerals and long chain n-3 and n-6 PUFAs (ARA, EPA, DHA). Oil extracted from microalgae have proven to successfully replace marine fish oil in diets for sea bream (Ganuza et al., 2008). Microalgae produced in controlled conditions using innovative photobioreactor technologies can supply products of constant and suitable quality to be included in aquafeed at relatively moderate prices. The marine microalga Isochrysis aff. galbana (T- ISO), showed high protein quantity and quality, lipids rich in LC-PUFA, DHA in particular, and a good vitamin pattern, therefore could have the potential to become a sustainable alternative dietary source and contribute to meet the increasing demand for fish meal/oil that is a critical limiting factor for the future expansion of aquaculture activities. A study was carried out to evaluate growth response, feed utilization and quality traits of the edible portion of sea bass (Dicentrarchus labrax) fed organic diets including dried Isochrysis aff. galbana (T-ISO). Three test isoproteic (50% DM) and isolipidic (18% DM) diets were compared. All preparations were formulated using "organic" ingredients. Isochrysis aff. galbana was incorporated to replace 10% (T- ISO10) and 20% (T- ISO20) protein supplied as dried fish meal which was the major protein source in the control diet (ORG). All diets were offered to apparent satiety to 12 groups of European sea bass juveniles under controlled environmental conditions (temperature 23\ub0C; salinity 28 psu; light-dark cycle 12L:12D) according to a completely random design. Feeding the test diets over 70 days resulted in similar fish growth and feed utilisation. Apparent digestibility coefficients (ADCs) were measured in vivo using acid insoluble ash as indigestible marker. The effects of the dietary algae inclusion on the fillet composition were also considered