The biomass of rotifers is used as live food in aquaculture; their quality is determined by the content of the main polyunsaturated fatty acids and the weight it acquires over time. The objective of this work was to evaluate the variables involved in this process to achieve higher quality. Within the rotifer culture, the following evaluations were carried out nine times (0, 12, 24, 48, 72, 96, 120, 144, 168 hr); with two types of food TRA = 0 (Nannochloropsis oceanica) and TRA = 1 (N.oceanica + Isochrysis galbana); assessing three types of fatty acids (μg/g) eicosapentaenoic (EPA; 20:5nÀ3), docosahexaenoic (DHA; 22:6nÀ3), and arachidonic (ARA; 20:4ωÀ6); and biomass weight in grams from 7,000 individuals per sample. The results showed that the maximum biomass weight was 77.5 g at 96 hr with the mixed treatment.In both treatments, the EPA and DHA fatty acid content exhibited the exact same temporal pattern, while ARA fatty acid was recorded during the entirety of the mixed treatment.The relationship of biomass weight over time versus the fatty acids exhibited significant differences in the mixed treatment, where an increasing trend over time is observed.

ResumenDebido a la gran facilidad con que las microalgas pueden capturar el CO 2 del medio ambiente, resulta interesante evaluar la cantidad y tiempo de ingreso de éste a los cultivos masivos, con la fi nalidad de aumentar la densidad celular. El objetivo del presente estudio fue evaluar los tiempos de inyección del mencionado gas, durante la producción de biomasa que conlleve a una mayor densidad celular, evaluando además, la variación del pH sin alterar la calidad del cultivo. A partir de seis cepas obtenidas del Banco de Germoplasma del Instituto del Mar del Perú, se realizaron cultivos tipo batch de 300L en invernadero, el tiempo de cultivo de la fase exponencial donde se realizaron las pruebas fue de tres días. Los datos se procesaron mediante el análisis del parámetro pendiente de la regresión lineal. Los resultados mostraron que la densidad celular es inversamente proporcional al tiempo de inyección de CO 2 al cultivo. La mayor densidad celular, en las diferentes cepas, se obtuvo a los 5min, excepto para las cepas Chaetoceros gracilis y Nannochloris maculata, las cuales obtienen la mayor densidad a los 10 y 15min, respectivamente. La variación de pH tendió hacia la acidez, en un rango de 8 a 4, sin alterar la densidad celular, por el contrario, los cultivos permanecieron libres de contaminantes. En conclusión, los resultados permiten establecer tiempos adecuados de inyección del CO 2 , los cuales fortalecen la fase de crecimiento exponencial aumentando la densidad poblacional en un 30% sobre lo establecido en esta fase.Palabras clave: microalgas, densidad celular, CO 2 , cultivo masivo. AbstractAs microalgae can capture CO 2 easily from the environment, it is interesting to measure the amount and time control of the entry of this gas into microalgae mass culture, in order to increase cell density. The aim of this study was to evaluate the injection times of CO 2 for biomass production that may lead to a higher cell density, it was also evaluated the pH variation without altering the quality of the crop. The work was made with six strains from the Germplasm Bank of the Instituto del Mar del Perú. There were performed cultures like 300L batch in a greenhouse, the cultivation time of the exponential phase lasted three days. The slope of the regression line parameters was analyzed to process data. The results showed that the cell density is inversely proportional to CO 2 injection time cultivation. The higher cell density 23 Cita: Oscanoa Huaynate AI, Ynga Huamán GA, Chang Ávila IL, Aguilar Samanamud CP. Impacto del CO 2 sobre la densidad celular en seis cepas de microalgas marinas. rev.ion. 2015;28(2):23-32.

Chlorophyte microalgae Dunaliella are halophilic flagellated cells; they can resist high salinities, producing β-carotene to balance osmotic stress. This pigment has important antioxidant properties for biotechnology, the prevention of tissue aging, the efficiency of the immune system, and sun protection against UV-B rays. The objective of this study was to characterize native strains of the genus Dunaliella from the Marine Institute of Peru, under the influence of stress factors for the production and concentration of β-carotene. Different tools were used to characterize these strains through molecular analysis, optimization of parameters for carotene accumulation, growth curves, life cycle, and carotene analysis. The accumulation of this pigment was mainly due to adaptation to salt stress. The differences between Dunaliella strains according to their population growth demonstrated that they did not have the same capacity to respond to the same cultivation conditions, although most of them are from the same species. The IMP-BG-001 strain, from Piura, can accumulate high concentrations of β-carotene