Flávio Luiz Honorato Silva

Dynamic modelling, simulation and optimization of an extractive continuous alcoholic fermentation process

The conventional alcoholic fermentation is a typical inhibitory process, leading to low productivity and yield. The ethanol produced inhibits yeast cells, causing a reduction in the alcohol production rate and cell growth rate. In this work, modelling and simulation have shown that continuous extractive fermentation, coupling a fermenter with an extractive vacuum flash chamber, is technically possible. In this case, the ethanol is partially removed, increasing drastically the productivity. Additionally, temperature control can be performed without using heat exchangers. The optimization was carried out using the method of factorial design and response surface analysis, leading to the determination of the most relevant variables, which were: 1.2 h residence time, 0.4 flash recycle rate, 180 g dm−3 sugar concentration and 0.35 cell recycle rate. The results, using optimized variables, were 98% conversion and 23 g dm−3 h−1 productivity, which represent a three times higher productivity than in a conventional continuous process. © 1999 Society of Chemical Industry

Equilíbrio higroscópico da palma forrageira: relação com a umidade ótima para fermentação sólida

In the study of the protein enrichment process of the cactus pear (Opuntia ficus-indica Mill) through the yeast Saccharomyces cerevisiae in semi-solid state fermentation, the water activity is one of the variables that most affects the fermentation process as well as the storage. The present work had the objective of obtaining isotherms of sorption of the cactus pear, in the usual temperatures of the fermentations processes, 30, 35 and 40 oC, in order to correlate water activity and moisture content. The obtained isotherms were analyzed by the GAB and BET models, the GAB model being, in general, the one that adjusted better to the experimental data. The isotherms allowed to find appropriate moisture content to obtain the water activities recommended for the fermentation process as well as during the storage of this enriched product.

Adsorption isotherms of the dry cashew apple

Water activity is a very important factor in a solid state fermentation process due to its relation with the water quantity available to the microorganism that will synthesize the product. Therefore, it is necessary to obtain the sorption isotherms for the characterization of the substrate. The objective of this study is to obtain adsorption isotherms of the dry cashew apple (Anacardium occidentale L.) at normal temperatures of fermentation process (25, 30, 35 e 40 oC). Five mathematical models were fitted to the experimental data: BET, GAB, Oswin, Henderson e Smith. The GAB model was better fitted to the product. The isotherms allowed the determination of the appropriate moisture content to obtain the water activities that maximize the biosynthesis of the microorganism for the pectin production by solid state fermentation process. The moisture content of the substrate should be above 35% d.b.

Characterization of polygalacturonase produced by solid-state fermentation using the residue of passion fruit as substrate

Pectinolytic enzymes, or pectinases, are a heterogeneous group of enzymes that hydrolyze the pectic substances present in plant cells. These enzymes are applied in several areas, making it important to know their characteristics for an efficient application. This work aimed to characterize the dry residue of passion fruit (Passiflora edulis) and subsequent characterization of the enzyme polygalacturonase produced by solid state fermentation and leavening agent and the filamentous fungus Aspergillus niger. The residue of passion fruit presented a pectin content of 13.10%, having a potential as a substrate for the production of pectinases. The activity of polygalacturonase reached a maximum value after 66 h of process with 40% initial moisture content and 1% of nitrogen supplementation. In this condition an activity of 20.9 U g-1 was obtained. The polygalacturonase produced the crude enzymatic extract presenting good thermal stability up to temperatures of 50 °C. This enzyme remained stable in the pH range between 3.5 and 5.5 and was not detected for pH values above 6.5.

Cinética de secagem do resíduo de abacaxi enriquecido

O Brasil e um dos maiores produtores de abacaxi do mundo e o maior da America do Sul. O fruto e a parte comercializavel da planta enquanto o restante e formado por caule, folha, casca, coroa e talos, considerado residuo agricola e nao tem sido devidamente aproveitado, resultando em perdas economicas. Caracterizar e avaliar a cinetica de secagem do residuo (casca) de abacaxi (Ananas comosus L.) enriquecido utilizando a levedura Saccharomyces cerevisiae em leito estatico, em camada fina de secagem, utilizando-se de planejamento experimental fatorial, foi o objetivo deste estudo. A temperatura (40 a 60 oC) e a velocidade do ar de secagem (0,8 a 1,3 m s-1) sao as variaveis do processo. O residuo enriquecido e caracterizado apresentou alto teor de materia seca (90,27%) e elevado teor de proteina (20,21%) em relacao ao residuo in natura (7,61%). A cinetica de secagem ocorreu no periodo de taxa decrescente. Os modelos Page, Henderson & Pabis e Lewis, ajustaram os dados experimentais satisfatoriamente, sendo Page discretamente superior aos demais. Verificou-se influencia da variavel temperatura apenas para a variavel resposta umidade, nao sendo observada influencia estatisticamente significativa da velocidade do ar de secagem.

Simulated Dynamics and Control of an Extractive Alcoholic Fermentation

In this study, we investigated the dynamics of a computer simulation of a continuous alcoholic fermentation process combined with a flash column under vacuum. The alcohol was partially extracted in order to maintain its concentration at about 40 kg/m3 in the fermentor. The mathematical model of the fermentation was developed for industrial conditions and considers the effect of the temperature on the kinetic parameters. The performance of the dynamic matrix control algorithm, single input single output and multiple input multiple output, for the control of the extractive process was studied. The concepts of factorial design were used in a simulation study to determine the best control structures for the process.

Isotermas de sorção do resíduo agroindustrial de casca do abacaxi (Ananas comosus L. Mer)

In the study of the protein enrichment process of ring pineapple (Ananas comosus L. Mer) through the yeast Saccharomyces cerevisiae and Aspergillus niger in solid state fermentation, the water activity is one of the variables that most affects the fermentation process as well as the storage of this enriched protein. The present work, had the objective of obtaing sorption isotherms of the pineapple peel residue in the usual temperatures of the fermentation processes, 25, 30, 35 and 40 oC, in order to correlate water activity and moisture content. The obtained isotherms were analyzed by the models of Henderson and GAB, being the GAB model, in general, the one that better adjusted to experimental data. The isotherms allowed to find appropriate moisture content to obtain the water activities recommended for the fermentation process as well as during the storage of this enriched protein.

Isotermas de adsorção e calor isostérico da palma forrageira enriquecida proteicamente

The protein enrichment of cactus pear through solid-state fermentation with the use of yeasts sought to increase the nutritional value of this forage so that it may be used as protein supplement for animal feed which may be offered either wet or dried and stored under appropriate conditions. The present work had its objective to study the adsorption isotherms of the protein enriched cactus pear, at temperatures of 30, 35 and 40 °C, to choose the mathematical model that best adjusted to experimental data and to determine the adsorption heat isosteric, looking for parameters for study of storage of this material. Starting from the obtained results, it was verified that the Henderson model was better if it was adjusted to experimental data adsorption isotherms at the three studied temperatures and that adsorption heat isosteric of studied product decreases with the increase of moisture content. For the storage of the enriched cactus pear it is necessary that the ideal range of activity of water should be between 0.25 - 0.35, which corresponds to moisture content (d.b.) smaller than 0.03, eliminating, this way, any growth of microorganisms.

Lixiviação de poligalacturonases obtidas pela fermentação semissólida da casca e albedo do maracujá-amarelo

Polygalacturonases enzyme was produced by solid state fermentation using as substrate the residue of passion fruit (Passiflora edulis flavicarpa) and as fermentation agent the mutant fungus Aspergillus niger CCT 0916. To optimize the recovery step of the enzymes, the values of the leaching parameters such as agitation, contact time and solvent/substrate relation were investigated with factorial experimental design 23. Agitation of 50 rpm, 45 min and relation 10:1 provided the best recovery results. The response surface analysis, showed that the residue of passion fruit is an adequate substrate for the production of polygalacturonase enzyme.

Evaluation of Cashew Apple Bagasse for Xylitol Production

In this chapter is presented the general features and theoretical foundations about the topic, as its importance, consequence and transformation of the lignocellulosic residues in biotechnological processes; xylitol and its importance in biotechnological production, fermentation process and kinetic study. After, are presented the procedures of the experimental study that aimed to evaluate the potential of the liquor obtained from the cashew apple bagasse, for the production of xylitol, through the fermentation kinetics and fermentative parameter. The experimental work has shown that C. guilliermondii was able to consume xylose in all fermentations performed with greater production of xylitol of 2953.19 mg/L in 12 h of fermentation, obtaining volumetric productivity of xylitol, the factor and the efficiency of conversion of xylose to xylitol 0.108 g/L h, 90.70 and 98.99 %, respectively.