Abstract Lipids extracted from microalgae for biofuel production have drawn the attention of researchers. Various methods for quantification of neutral lipids, such as solvent extraction or gravimetric, require a large volume of sample and are time-consuming. In this work, Nile Red was employed to evaluate the lipid content in microalgae Scenedesmus sp. through 2D fluorescence spectroscopy using chemometric modeling with a selection of wavelength pairs reducing the variable numbers. Cultivation of microalgae for 10 days was performed. Samples were taken starting after the 5th day of cultivation. Microalgae samples were dried using an oven with tangential airflow and the conventional Bligh and Dyer method for lipid extraction was employed. Before the measurement of fluorescence, the samples were diluted in ethanol at 40°C for 10 minutes, and then Nile Red solution (10 µg/mL ethanol) was added. The results of lipid quantification using the proposed technique achieved mean absolute percentage error (MAPE) lower than 5% and correlation coefficients around 0.99 in the test phase. Linear models using four excitation-emission pairs of fluorescence were fitted and were selected based on Pure Spectral Chemometric Modelling (PSCM). The method for lipid quantification using predictive linear models and 2D fluorescence proved to be robust and fast (requiring less than 30 min) compared to the conventional gravimetric method (which takes at least 5 hours) to obtain comparable results.

ABSTRACT Y-rank can present faults when dealing with non-linear problems. A methodology is proposed to improve the selection of data in situations where y-rank is fragile. The proposed alternative, called k-rank, consists of splitting the data set into clusters using the k-means algorithm, and then apply y-rank to the generated clusters. Models were calibrated and tested with subsets split by y-rank and k-rank. For the Heating Tank case study, in 59% of the simulations, models calibrated with k-rank subsets achieved better results. For the Propylene / Propane Separation Unit case, when dealing with a small number of sample points, the y-rank models had errors almost three times higher than the k-rank models for the test subset, meaning that the fitted model could not deal properly with new unseen data. The proposed methodology was successful in splitting the data, especially in cases with a limited amount of samples.

ABSTRACT Operational KPIs play an extremely important role in the process industry, aiding in decision making. However, they need to be reliably calculated to be representative. The present work presents a schematic methodology for the calculation of these KPIs, including techniques of steady-state detection, denoising, error propagation and sensitivity analysis, presented, as far as it is known, in the form of a new graphical tool proposed by the authors named StatSSCandlePlot. The methodology was applied in a real case study of a gas fired boiler in which the indicator studied was its efficiency evaluated by the Stack Loss Method. From the StatSSCandlePlot it was possible to identify the trends of the indicator, the portion of each window in the steady-state, the values to be considered from the indicator and, in a complementary way, to identify the variable that most influences the variation of the indicator, through the sensitivity analysis.

ABSTRACT One of the research lines related to active packaging takes into account the incorporation of antimicrobial agents such as chitosan, a polysaccharide derived from the crustaceans’ exoskeleton. However, because of chitosan high molar mass, its diffusion from the package to the food surface is restricted, so the use of oligomers is an interesting but less investigated alternative. The purpose of this work was to obtain active films based on thermoplastic corn starch (TPS) by adding oligochitosans (OC, molar mass = 290 g mol-1 and degree of polimerization = 2). Films were thermo-compressed in a hydraulic press. Diffusion assays of OC from TPS matrix to liquid medium with different acidity degree (pH = 3, 5, and 7) were performed. Liquid medium conditions were selected according to the acidity of a wide variety of foods. From these assays, oligomers diffusion capacity and the dependence with pH were demonstrated. The efficiency of OC incorporation in packaging material was compared to the corresponding to the conventional method by food spray with a solution of the active agent. The antimicrobial capacity of films and OC solutions was evaluated from the count of yeasts and molds, using fresh strawberries as food product. Obtained results from these experiments showed the active character of films based on TPS and OC, and a greater efficiency of antimicrobial active packaging compared to the conventional methods.

RESUMEN Una de las líneas para el desarrollo de envases activos contempla la incorporación de agentes antimicrobianos como el quitosano, polisacárido derivado del exoesqueleto de crustáceos. No obstante, su elevada masa molar restringe su difusión desde el envase hacia el alimento por lo que el empleo de oligómeros de características diferenciales es una alternativa interesante, aún poco investigada. El objetivo de este trabajo fue obtener películas activas a base de almidón de maíz termoplástico (TPS) mediante la incorporación de oligoquitosanos (OQ, masa molar = 290 g mol-1 y grado de polimerización = 2). Estos materiales fueron obtenidos mediante termo-compresión en una prensa hidráulica. Se realizaron ensayos de difusión de los OQ desde la matriz de TPS hacia un medio líquido con diferentes grados de acidez (pH = 3, 5 y 7). Las condiciones del medio líquido fueron seleccionadas según la acidez de una amplia variedad de alimentos. A partir de estos ensayos, se demostró la capacidad de difusión de los oligómeros y su dependencia con el pH del medio. La eficiencia de la incorporación de los OQ en el material de envase se comparó con la correspondiente al método convencional de spray del alimento con una solución del agente activo. La capacidad antimicrobiana de las películas y de las soluciones de OQ se evaluó a partir del recuento de hongos y levaduras, empleando frutillas frescas como alimento de estudio. Los resultados derivados de estos ensayos evidenciaron el carácter activo de la película desarrollada, demostrándose además la mayor eficacia del uso de envases activos antimicrobianos, respecto de los métodos convencionales.

This study evaluated the feasibility of using vinasse as a nutrient source for microalgae cultivation. The Scenedesmus sp was grown in a medium supplemented with vinasse and process variables were optimized using a factorial design and a Central Composite Design (CCD). The factorial design results showed that it was possible to cultivate microalgae at concentrations of up to 40% of vinasse in the culture medium. The CCD results showed that the light intensity and vinasse concentration influenced the amount of biomass produced.

This study aimed at evaluating the best conditions for lipid accumulation in the marine microalga Nannochloropsis oculata in an airlift photobioreactor. Experiments were carried out following a central composite design with the following variables: temperature (19 to 29°C), sodium nitrate concentration (NaNO3) in the culture medium (f/2) (25 to 125 mg.L-1) and incident light intensity (49 to 140 µE.m-2s-1). The maximum lipid production was 132.4 mg.L-1 under the following conditions: 27°C, NaNO3 concentration 105 mg.L-1 and 122 µE.m-2.s-1, which was 30% of dry weight of the biomass.

O principal objetivo deste trabalho é a busca de uma solução mais eficiente e ambientalmente correta para a indústria do curtimento do couro (curtumes). Os curtumes são indústrias altamente consumidoras de águas e enfrentam sérios problemas com a geração de efluentes. Neste artigo, avaliaram-se alternativas de reuso da água de processo, as quais foram obtidas através da resolução de um problema de programação não-linear, visando minimizar o consumo de água em curtumes, mantendo a qualidade do produto final. Os resultados alcançados foram muito promissores e apontam para um potencial significativo de redução no consumo de água. Baseado no simples reuso de correntes, o consumo de água já pode ser reduzido significativamente, em torno de 70%. A solução obtida, além de reduzir o consumo de água, diminui significativamente o consumo de reagentes químicos e consequentemente a carga de poluentes a serem tratados posteriormente.

The aim of this work was to look for an efficient and environmentally safe solution for the leather tanning industry through a problem of non-linear programming. The results were promising and showed a significant potential of wastewater reduction. Reuse of internal streams reduced around 70% wastewater. The solutions obtained could reduce significantly the amount of chemicals and consequently the amount of waste to be treated.