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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 (rETR(max)) 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.

Several high-value microalgal products have become well established, and there are opportunities for additional new ones. Microalgae are also playing an increasing role in cosmeceuticals, nutraceuticals, and functional foods. In this chapter the effects of the main environmental factors on the productivity and biochemical composition of microalgal biomass are summarized. Particular emphasis has been devoted to the environmental factors limiting the full exploitation of the photosynthetic capacity of the cultures. Among these, light saturation remains the main obstacle to economical exploitation of microalgae production potential. Other important limiting environmental factors are represented by sub- and supraoptimal temperatures. The effects of environmental factors on productivity are further enhanced when they act in synergy. The opportunity to improve light utilization by increasing the mixing rate and the effective possibility to take advantage of intermittent light are discussed in detail in relation to the culture system. Independently of the strain to be produced, the overall production system must be approved for the “food industry”; this regulatory compliance involves the materials, systems, and protocols used during production. These aspects are reviewed in the final part of the chapter.

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/publishedVersion

The aim of this study was to evaluate nutrient digestibility, growth response, carcass and fillet yields, muscle tissue composition and skin colour appearance of European sea bass (D. labrax) fed graded levels of a mixture of Tisochrysis lutea and Tetraselmis suecica freeze-dried biomass in partial substitution for fish meal and oil in diets containing substantial levels of vegetable oils and protein-rich derivatives. Five complete diets were formulated to be grossly isoproteic and isolipidic and prepared by including a blend of the two freeze-dried microalgae biomass in a 2:1 weight ratio, to replace approximately 15, 30 and 45% fish meal protein and 12, 24 and 36% fish lipid of a positive control diet. A negative control complete feed high in soybean meal was also prepared. Each diet was offered in triplicate, during 105 days until visual satiety of fish (204 ± 12.7 g) kept in a semi-closed recirculating marine water system ensuring optimal water quality to E. sea bass. The results of the study have shown that replacing about 45% crude protein and 36% lipid from fish meal and lipid by a mixture of Tisochrysis lutea and Tetraselmis suecica dried biomass, did not adversely affect growth performance and feed conversion efficiency of European sea bass. A slight decline in dry matter, protein and energy digestibility occurred in response to graded levels of dietary microalgae biomass, which was compensated by increased feed intake. Moreover, the diet including the dried microalgae resulted in a higher nutritive value than that of the negative high-soybean meal control feed. No major changes were observed in biometry traits and slaughter yield while the nutritional properties of the edible muscle tissue were little affected in terms of n-3 PUFA. The presence of the dried microalgae in the diet resulted in a greenish pigmentation of the skin, with a slight tendency towards redness and diminished lightness and hue. Overall the results obtained here reveal a potential improvement in sustainability in terms of reduced reliance on halieutic feed resources in case of the microalgae-containing diets. Hence the sustainable use of the dried mixture of the 2 marine microalgae biomass as feed ingredients in diets for the E. sea bass seems to be mainly limited by the low availability and unaffordable market price which are both expected to improve over the next 10 years.

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 ± 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, 5-27%; GE, 12.5--22.6 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 (64-73%; 51-59%, respectively) compared to a second group including P. purpureum, T. lutea and cyanobacteria (CP-ADC, 83-88%; GE-ADC, 74-90%) 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 cost-effective, hence attractive for the feed-mill industry in the near future.

The annual productivity of Tetraselmis suecica in a 1-ha Green Wall Panel-II (GWP-II) plant in Tuscany (Italy) is 36 t (dry weight) ha−1 year−1, which corresponds to an energy output of 799 GJ ha−1 year−1. The energy inputs necessary to attain that productivity amount to 1362 GJ ha−1 year−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 66 t ha−1 year−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 600 GJ ha−1 year−1. Marine microalgae cultivation in a GWP plant, in a suitable location, can attain high biomass productivities and protein yields 30 times 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.

The aim of this study was to evaluate nutrient digestibility, growth performance, biometry, dressing out parameters, fillet muscle proximate and fatty acid composition of European sea bass (Dicentrarchus labrax, L.) of nearly marketable size, fed increasing levels of a freeze-dried biomass of Isochrysis sp. (clone T-ISO) as a partial substitute for protein and lipid from fish derivatives, in diets where the level of n-3 long chain (LC) PUFA were reduced through a partial replacement of fish oil for crude palm oil. Since diets including the test ingredients could possibly result in changes of certain quality attributes, fish were also subjected to overall sensory evaluation by a trained panel of assessors according to a triangle test. Three diets were formulated to be grossly iso-nitrogenous (N, 7.5 % dry matter). A preparation in which fish meal/trimmings and fish oil were the major protein and lipid sources was used as a positive control diet. Two test complete diets were obtained from the control preparation so that approximately 10 and 20% crude protein from a high quality fish meal and 18 and 36% lipids from fish oil were supplied by the dried microalgae biomass. To stress the role of Isochrysis sp. as a source of n-3(LC)PUFA, the diets including increasing levels of the microalgae biomass were made grossly iso-caloric-lipidic by replacing a part of fish oil with palm oil which is known to be virtually free from n-3 PUFA. Each diet was fed to apparent satiety to quadruplicate groups of sea bass (142 g) over 121 days. The results have shown that replacing up to 20% crude protein from fish meal with a dried Isochrysis biomass and up to 36% fish lipid for those supplied by the microalgae in a diet with reduced level of fish oil, did not adversely affect feed intake or growth performance relative to controls even if the highest substitution rate resulted in a decline (P

The haptophyte Pavlova lutheri was cultivated in a 4-l flat alveolar photobioreactor (FAP) in semi-continuous mode during 35 days, achieving a mean volumetric productivity of 0.4 g l-1 day-1. The microalgal culture was harvested from the photobioreactor at an average concentration of 3.5 g l-1 and subjected to different storage conditions in which the effects of temperature (1 °C, 4 °C and 25 °C), air supply and preservative (ascorbic or propionic acid) addition on the viability of the stored suspensions were investigated. Low temperatures (1 and 4 °C) and air-bubbling extended the shelf-life of the stored suspension, while no beneficial effects of ascorbic or propionic acid were found. The influence of temperature and air-bubbling on fatty acid content and profile was also evaluated over a 23-day period of storage. Air-bubbled suspensions exhibited, on the average, a 70% decrease of total fatty acid content (TFA) during storage. Non-bubbled suspensions showed a much lower decrease. The decrease mainly involved the saturated 14:0 and 16:0 and the monounsaturated 16:1n-7 and 18:1n-9. The polyunsaturated eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA) decreased significantly only at the end of the storage period. A feeding trial on Pacific oyster (Crassostrea gigas) larvae was carried out with fresh and preserved P. lutheri biomass kept under the best storage conditions previously defined (1 °C; darkness; air-bubbling). After 14 days of rearing no significant differences in growth or survival were detected when fresh or preserved P. lutheri was used in a monospecific diet or in association with the diatom Chaetoceros calcitrans forma pumilum.

Aquaculture production could be improved by using preserved microalgal biomass as feedstuff for marine animal larvae and juveniles. The present paper reports the effects of preserving Tetraselmis suecica by freezing with and without cryoprotectant, freezing in liquid nitrogen and maintenance of concentrated cultures at 4 °C on viability and fatty acid profile. For long-term preservation (as long as 21 months), freezing can keep the fatty acid profile unaltered although leading to complete loss of cell viability. On the other hand, concentrated cultures kept in darkness at +4 °C show a strong capacity for survival closely correlated with cell concentration. At 4 g · l −1 , residual photosynthetic activity (ca. 6% of the initial) was still present after 150 days of storage. Furthermore, oxygen availability affected cell survival. Cultures stored in hermetically sealed vials lost their viability much more rapidly than those kept in cotton-plugged vials. Dry weight percentages of all fatty acids slightly increased in stored biomass in comparison with fresh biomass, because of reserve material consumption. Nonetheless, the fatty acid profile on a total fatty acid basis remained unchanged over storage time regardless of viability. This is an important fact to bear in mind as fatty acids play an important role in the quality of the cell as food in aquaculture.

Dried Tetraselmis suecica was evaluated as a fish protein substitute when incorporated to replace (protein basis) 10% (TETRA10) and 20% (TETRA20) of the control diet. The diets were offered to nine groups of European sea bass (72 g) over 63 days. Test diets did not affect zootechnical performances nor carcass or fillet yields and proximate analysis of edible portion. Feeding TETRA20 resulted in lower apparent digestibility coefficients of protein, lipid, and organic matter, and hepatosomatic index compared to the control diet. T. suecica was able to replace up to 20% of fish protein without hampering growth performance and major quality traits of sea bass.

Scenedesmus sp. cultivated under laboratory conditions in secondarily-treated urban wastewater attained a mean productivity of 20·1 g (dry wt) m−2 day−1 and the complete removal of nitrogen and phosphorus from the effluent in a 24 h cycle. A Daphnia magna population inoculated into the Scenedesmus sp. suspension exhausted the microalgae in 48–72 h and achieved productivity levels of up to c.3 g (wet wt) litre−1 week−1, a maximal food conversion efficiency of 0·44 mg mg−1 and efficiencies of nitrogen and phosphorus incorporation varying from 40·6 to 49·5% and from 69·5 to 85·2%, respectively. When the D. magna cultures were kept under continuous illumination instead of under light-dark cycles or in darkness, the biomass yield, the food conversion efficiency and the efficiency of incorporation of nutrients increased significantly, showing that, in the light, Scenedesmus sp. cells were able to use the daphnid excreta as a source of nutrients for growth.

The use of fungicides for seed and shoot preservation resulted in a strong selection of micro-organisms in the spermosphere. Many free-living nitrogen fixing bacteria have been proved to be affected by these agrochemicals (i.e. Captan, Carboxin at concentration of 50 – 100 μg/ml and up), thus being discriminated in the early stage of root colonization.

A useful method to reduce the input of chemical fertilizers in agriculture and to control the soil and water pollution may be represented by the use of asymbiotic nitrogen fixing micro-organisms as biological fertilizer. Extensive experimentation so far carried out under different environmental conditions has generally put in evidence some positive effects of inoculation on the production of various cereals and other crops.

Autotrophic microalgae cultures have been proposed as an alternative source of EPA, a nutritionally important polyunsaturated fatty acid that plays a key role in the prevention and treatment of several human diseases and disorders. The technology currently available is however, considered commercially not viable because of the low degree of control of algae cultures in outdoor open ponds. The use of closed reactors could overcome these limitations and bring EPA production by microalgae closer to becoming a reality. In this study, we have demonstrated the feasibility of outdoor cultivation of Nannochloropsis sp. in tubular reactors and the potential of this eustigmatophyte as an alternative source of EPA. Nannochloropsis sp. was cultivated in NHTRs of different sizes (from 10.2 to 610 1) from spring to autumn under the climatic conditions of central Italy. EPA productivity essentially reflected the productivity of the culture and reached its maximum in May-June (mean monthly value: 32 mg l− 1 day− 1). Although the fatty acid composition of the biomass varied significantly during the cultivation period, EPA content remained rather stable around the value of 4% of dry biomass. The transfer of the cultures from laboratory to outdoor conditions, the exposure to natural light-dark cycles, along with lowering the salt concentration from 33 g l− 1 (seawater salinity value) to 20 g l− 1, factors that caused lasting modifications in the fatty acid content and composition of Nannochloropsis sp., did not significantly affect the EPA content of the biomass.