Nitrogen starvation for lipid accumulation in the microalga species Desmodesmus sp.

Recently, to obtain lipids from microalgae has been the object of extensive research, since it is viewed as a promising feedstock for biodiesel production, especially when compared with crops such as soybean and sunflower, in terms of theoretical performance. The reduction of nutrient availability in culture media, especially nitrogen, stresses the microorganisms and affects cell growth, thus inducing lipid accumulation. This is an interesting step in biodiesel feedstock obtention from microalgae and should be better understood. In this study, four levels of nitrogen concentration in the BG-11 culture medium were evaluated in the growth of the chlorophycean microalga Desmodesmus sp. Both cell growth and lipid content were monitored over 7 days of cultivation, which yielded a final cell density of 33 × 10(6) cells mL(-1) with an initial NaNO3 concentration of 750 mg L(-1) in the medium and a maximum lipid content of 23 % with total nitrogen starvation. It was observed that the microalgae presented high lipid accumulation in the fourth day of cultivation with nitrogen starvation, although with moderate cell growth.

Biofuels from continuous fast pyrolysis of soybean oil: a pilot plant study.

The continuous fast pyrolysis of soybean oil in a pilot plant was investigated. The experimental runs were carried out according to an experimental design alternating the temperature (from 450 to 600 degrees C) and the concentration of water (from 0% to 10%). The liquid products were analyzed by gas chromatography and by true boiling point (TPB) distillation. A simple distillation was used to obtain purified products such as gasoline and diesel. Physical-chemical analysis showed that these biofuels are similar to fossil fuels. Mass and energy balances were carried out in order to determine the vaporization enthalpy and the reaction enthalpy for each experiment. The thermal analysis showed that it is possible to use the products as an energy source for the process.

Analysis of kinetic and operational parameters in a structured model for acrylic acid production through experimental design.

In biotechnological processes, a great number of factors can influence the income productivity and conversion. Normally, it is not evident which of these factors are the most important and how they interact. In this work, multivariate analysis techniques are used as experimental design coupled to a detailed deterministic model to identify the parameters with the most significant impact on the model to represent well the acrylic acid production process. It is proposed as an alternative process, having sugarcane as feedstock, to the petrochemical-based ones that have significant environmental impacts for their production. To increase the competitiveness of renewable acrylic-acid-based process, it is necessary to find out working conditions near the optimal region, which is not an easy task, as the process is multivariable and non-linear. The mapping of the dynamics of the developed process is made using techniques of factorial design together with the methodology of Plackett-Burman. It is shown that it is possible to increase the process performance by choosing optimized conditions for the reactor operation.

Evaluation of liquid-liquid extraction process for separating acrylic acid produced from renewable sugars.

In this article, the separation and the purification of the acrylic acid produced from renewable sugars were studied using the liquid-liquid extraction process. Nonrandom two-liquids and universal quasi-chemical models and the prediction method universal quasi-chemical functional activity coefficients were used for generating liquid-liquid equilibrium diagrams for systems made up of acrylic acid, water, and solvents (diisopropyl ether, isopropyl acetate, 2-ethyl hexanol, and methyl isobutyl ketone) and the results were compared with available liquid-liquid equilibrium experimental data. Aspen Plus (Aspen Technology, Inc., version 2004.1) software was used for equilibrium and process calculations. High concentration of acrylic acid was obtained in this article using diisopropyl ether as solvent.

A new process for acrylic acid synthesis by fermentative process.

With the synthesis of chemical products through biotechnological processes, it is possible to discover and to explore innumerable routes that can be used to obtain products of high added value. Each route may have particular advantages in obtaining a desired product, compared with others, especially in terms of yield, productivity, easiness to separate the product, economy, and environmental impact. The purpose of this work is the development of a deterministic model for the biochemical synthesis of acrylic acid in order to explore an alternative process. The model is built-up with the tubular reactor equations together with the kinetic representation based on the structured model. The proposed process makes possible to obtain acrylic acid continuously from the sugar cane fermentation.