Three experimental diets were formulated to contain 33 g kg−1 seaweed meals, made of wild brown algae (kelps) Macrocystis pyrifera (MAC) and Ascophyllum nodosum (ASC) or of a cultivated green alga Ulva clathrata (ULVA). The diets were fed to juvenile white shrimp Litopenaeus vannamei (1.6 g) for 28 days. Loss of dry matter (LDM) and loss of protein (LP) after 1 hour immersion in seawater, and distilled water absorption (WA) were analyzed in the pelleted diets, as well as shrimp weight gain, feed intake, feed conversion ratio (FCR), survival, protein efficiency ratio (PER) and body pigmentation. Feed intake, FCR and PER were corrected for nutrients preprandial losses in seawater. ULVA diet resulted in lower LDM, but a higher LP and also higher WA, indicating a modification of the pellet physical quality (better hydro stability). No significant differences in feed consumption and survival were found, but ULVA diet resulted in a slightly higher final weight (4.8 for ULVA versus 4.6 and 4.3 g for ASC and MAC), and better FCR (1.7 versus 1.9 and 2.1) and PER (2.0 versus 1.7 and 1.5), the differences with MAC diet being significant (Duncan, α = 0.05). Red color after cooking was markedly darker in the ULVA fed shrimp.
Abstract.-This review discusses microalgae assimilation of C, N and P as affected by pH-dependent factors ( solubility, ionization state and bioavailability) and CO 2 enrichment in tertiary water treatment during microalgae biomass production. This study indicates the importance of monitoring critical conditions such as: 1) pH and inorganic carbon species interaction; 2) P bioavailability; 3) nitrogen removal through NH 3 volatilization and 4) NH 3 toxicity. Also, optimal CO 2 enriched air considerations, such as: 1) combining intermittent and variable CO 2 enrichment to avoid losses into the atmosphere; 2) preventing microalgae growth inhibition due to H 2 CO 3 formation and pH acidification at early stages of the culture and 3) maintenance of optimal pH ( 8.5) through the buffer system (CO 2 / HCO 3 -). Finally, we suggest that biological technologies based on microalgae culture to remove excessive nutrient loads and compliance with environmental law s from water, represent a viable alternative attached to recycling and revaluation of resources through the generation and potential uses of biomass (e.g., fertilizer, pigments and antioxidants).Key words: Microalgae, MWTP effluents, nutrient recycling, tertiary wastewater treatmentResumen.-Esta revisión analiza la asimilación de C, N y P por microalgas y la influencia de los factores dependientes del pH (solubilidad, estado de ionización y biodisponibilidad), así como la adición de CO 2 y su interacción en el tratamiento terciario de aguas municipales durante la producción de biomasa de microalgas. Este estudio destaca la importancia de monitorizar condiciones críticas como: 1) la interacción entre el pH y las especies de carbono inorgánico; 2) la biodisponibilidad de P; 3) reducción de N por formación de NH 3 y 4) toxicidad de NH 3 . Por otra parte, para el uso óptimo de aire enriquecido con CO 2 se recomienda considerar: 1) el suministro intermitente y variable de CO 2 para evitar pérdidas a la atmósfera; 2) optimizar el consumo de CO 2 evitando la acidificación del pH por formación de H 2 CO 3 e inhibición de las microalgas en etapas tempranas de cultivo; y 3) conservación de pH óptimo ( 8,5) a través del sistema de amortiguamiento CO 2 / HCO 3 -. Finalmente, se sugiere que las tecnologías biológicas basadas en el cultivo de microalgas para la eliminación de nutrientes y cumplimiento de normativas ambientales, representan una alternativa viable, que une el reciclaje y revalorización de recursos a través de la generación y usos potenciales de la biomasa (e.g., fertilizantes, pigmentos y antioxidantes).Palabras clave: Microalgas, efluentes PTAR, reciclaje de nutrientes, tratamiento terciario de efluentes
This study was carried out to determine the persistence of toxicity of fermentation extracts of Bacillus thuringiensis var. israelensis after more than three decades of storage. For this purpose, a population of Aedes aegypti was established. The mortality rate of 20 spore-crystal extracts purified using the acetone-lactose coprecipitation method was measured and evaluated by bioassays according to a modified WHO protocol. The extracts with the highest mortality rate were determined in triplicate by their LD50 and LD98. All extracts showed toxicity at the highest tested dose (1000 ppm) and some, such as strains 3260 and 3501, still killed larvae at doses as low as 0.01 ppm. These data are surprising because no study on the activity of B. thuringiensis toxic proteins after such a long storage time has been reported.
Recent research has shown that the use of biological extracts, which contain a wide variety of nutrients and phytohormones are potentially useful in the production of plants of agricultural importance. Seaweed extracts are particularly rich in minerals and micronutrients necessary for the growth of microalgae. The effect of three commercial extracts of Ascophyllum nodosum as plant growth inducers (Stimplex®, Acadian Soils® and Liquid Seaweed Concentrate®), provided by Acadian Sea Plants Ltd., were evaluated in relation to the growth and production of biomass and carotenoids in Haematococcus pluvialis. The results were evaluated by one-way ANOVA and post-hoc analysis utilizing Tukey's test with a significance level of 95% (α= 0.05). The reference medium used was the Bold basal medium, to which 250 ppm of each extract was added. The Stimplex® extract had an increase of 22.79% in cell density and 17% in dry matter, higher than the control culture. The content of carotenoids and antioxidant capacity, respectively, with Stimplex® was 30.05% and 141.76% higher than the control culture.
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