Aplicação da metodologia de planejamento fatorial e análise de superfícies de resposta para otimização da fermentação alcoólica

In the present work, the influence of the amount of nitrogen and phosphorus and degrees Brix on the yield and productivity of alcoholic fermentation has been evaluated. The methodology used was factorial design and response surface analysis. Within the range studied only for phosphorus a statistically significant effect was observed. The broth of sugar cane of the CB 453 variety already possessed enough nitrogen for the fermentation. The mathematical and empirical model was validated for productivity and not for yield. The concentration of alcohol produced in the fermentation was not enough to cause cellular growth inhibition.

Desenvolvimento de metodologia analítica para determinação de colesterol em ração para ruminantes através de planejamento experimental fatorial

A chromatographic method was developed for cholesterol determination in feed for ruminants using response surface methodology. Among the five approaches of sample preparation methods tested, the saponification of the sample without heating presented less interference in the gas chromatography. The method presented a relative standard deviation (RSD) of 4.3%, recoveries between 84 and 87% and detection limit of 0.001 mg of cholesterol per g of feed.

Predição da demanda química de oxigênio em chorume maduro contendo reagente de Fenton, por meio de modelo matemático empírico gerado com planejamento fatorial completo

COD is an important parameter to estimate the concentration of organic contaminants. The closed system technique with the use of K2Cr2O7 is the most important one, however, it has the inconvenience to suffer positive chemical interferences from inorganic compounds such as Fe2+ and H2O2 (not enough reported in the literature). This paper considers a statistical-experimental set capable to validate a empirical mathematical model generated from a 23 experimental design, in the presence of Fe2+ and H2O2. The t test shows that mathematical model has 99,99999% confidence degree and the experimental validation test indicates absolute mean error of 4,70%.

Medidas de tensão superficial pelo método de contagem de gotas: descrição do método e experimentos com tensoativos não-iônicos etoxilados

Surface tension knowledge of surfactants aqueous solutions is important during amphiphilic molecule manufacturing and new product development, as feedback information to handle synthesis parameters to target performance. Drop counting method is an interesting simplification of drop weight method for surface tension measurements. A simple laboratory measurement device, with capability for temperature control, was assembled to allow investigation of ethoxylated surfactants. The implementation of the method was preceded by a detailed investigation of two factors that may affect the measured surface tension: drop formation velocity and surfactant ethoxylation degree. The limitations of the method are discussed on this basis.

Aplicação de planejamento fatorial a protocolo de extração e fixação de sulfetos volatilizáveis por acidificação (SVA) em amostras de sedimento

The AVS is defined operationally as acid volatile sulfide, which is a controlling phase on the partition of some metallic species in sediments. A Factorial design was evaluated by means of 16 experiments and using four variables: temperature, extraction time, N2 flow, and volume of the S2- collection solution. The factors that contributed to the efficiency of the process were the extraction time and the N2 flow. Trapping of S2- was efficient in AAB. The S2- was quantified using a potentiometric procedure. Recovery tests for S2- concentrations varying from 1×10-5 to 1×10-4 mol L-1 were in the range from 93 to 116%.

Efeito da adição de precursores na produção de alcaloide anticancerígeno usando a técnica de planejamento experimental

The effect of precursors on the anticancer alkaloid production by submerged fermentation using M. anisopliae 3935 was studied, according to complete experimental design 2² with three central points. The results showed that lysine was the most important variable, however, when both lysine and glucose were added to the fermentation medium, the alkaloid production reached, approximately, 17 mg L-1 after 120 hours of fermentation. Then, the scale-up of the process was carried out and these results were confirmed. Finally, 35 mg L-1 of alkaloid at 192 h were attained after increment of added aminoacid lysine.

Utilização de resíduos agroindustriais para a produção de proteases pelo termofílico Bacillus sp em fermentação submersa: otimização do meio de cultura usando a técnica de planejamento experimental

Thermophilic Bacillus sp. SMIA-2, produced protease when grown on apple pectic, whey protein and corn step liquor medium, whose concentration was varied from 3 to 10 gL-1, according to the central composite design 2³. The experiments were conducted in shaker, at 50 °C, 150 rpm and initial pH 6.5. The results revealed that the culture medium affected both, cell growth and enzyme production. After graphical and numerical optimization procedure, the enzyme production reached its maximum value at 30 h fermentation, reaching, approximately, 70 U protein mg-1, suggesting that this process was partially associated to the growth.

Otimizaçâo das condições de preparação de eletrodos à base de carbono cerâmico utilizando-se planejamento fatorial

Different parameters of carbon ceramic electrodes (CCE) preparation, such as type of precursor, carbon material, catalyst amount, among others, significantly influence the morphological properties and consequently their electrochemical responses. This paper describes a 2³ factorial design (2 factors and 3 levels with central point replicates), which the factors analyzed were catalyst amount (HCl 12 mol L-1), graphite/precursor ratio, and precursor type (TEOS - tetraethoxysilane and MTMOS - methyltrimetoxysilane). The design resulted in a significant third order interaction for peak current values (Ipa) and a second order interaction for potential difference (ΔE), between thefactors studied, which could not be observed when using an univariated study.

Utilização de planejamento fatorial no preparo de amostras de detergente em pó para a determinação de fósforo por análise em fluxo

The decomposition of detergent powder samples in a microwave oven and autoclave was evaluated. To establish the best experimental conditions a 2(5) factorial design was performed, varying the conditions in autoclave and microwave digestion and flow system parameters for the determination of phosphorus. The best composition was: 0.2 mL sulfuric acid; 500 W power and a 2 min time interval; 6 mmol L-1 of ascorbic acid and 16 mmol L-1 of molybdate to flow system. This factor levels use less reagents than the reference method. No statistically significant differences were found between the autoclave and microwave oven responses at the 95% confidence level.

Estabelecimento de condições para ensaio de dissolução de cápsulas de cinarizina empregando planejamento fatorial

This work describes the establishment of dissolution test conditions for 75 mg cinnarizine capsules using a multivariate approach. A 2³ full factorial design was carried out to achieve the best conditions and HCl 0.1 mol L-1 as dissolution medium, basket as apparatus at 100 rpm and collect time at 30 min were considered adequate. The quantification was carried out by spectrophotometry at 251 nm. Both dissolution procedure and analytical method were validated and all parameters were within the acceptable limits. Since there is no official monograph for this pharmaceutical product, this dissolution test could be applied for quality control routine.

Planejamento experimental na otimização da extração dos frutos de Syzygium cumini (L.) skeels

The aim of this study was to standardize the extractive solution of Syzygium cumini. The extractive solution was selected through a full factorial design, considering the extraction method (maceration-5-days, turbo extraction, percolation), extractor solvent (ethanol 50, 70, 96%) and plant material particle size 0.302 mm into a plant:solvent ratio (1:10), using the dried residue and antimicrobial activity determination as evaluation criteria. The tests were performed in triplicate. It appeared that the percolation is the best procedure extractive, and ethanol mixture: water (50:50) the best solvent. ANOVA analysis showed the importance of these parameters.

Planejamento fatorial e superfície de resposta: otimização de um método voltamétrico para a determinação de ag(i) empregando um eletrodo de pasta de nanotubos de carbono

A factorial design applied in a voltammetric stripping method for the measurement of Ag(I) in natural water is described. The procedure is based on the effective pre-concentration of silver ions on electrode surface. The calibration graph was linear in the silver concentration range from 7.92 x 10"7 to 1.07 x 10"5 mol L"1 with a detection limit of 3.81 x 10-7 mol L-1. The determination of Ag(I) in natural water samples was carried out satisfactory with the proposed electrode.

Otimização das condições de extração de saponinas em Ampelozizyphus amazonicus usando planejamento experimental e metodologia de superfície de resposta

This works describes the use of experimental design and surface response methodology for optimization of saponin extraction from Ampelozizyphus amazonicus. For this purpose, a method employing extraction based on maceration assisted by ultrasound technique was utilized. The following factors were studied: extraction length of time and solvent composition. The total saponin was determined by using a gravimetric method and the results expressed by their relative proportion to total crude extract. For the specific condition, 60% hydro-alcoholic solution and 18 minutes extraction length of time has shown the best results. This method can be useful for extraction of substances with biological importance

Determinação da constante de dissociação (Ka) do captopril e da nimesulida: experimentos de química analítica para o curso de farmácia

This paper presents the determination of the dissociation constant (Ka) of captopril and nimesulide as contextualized experiments to teach chemical concepts to students of Pharmacy. Captopril is an antihypertensive drug, which presents high water-solubility and weak acid properties. The pKa of carboxylic acid group of captopril is 3.7. Nimesulide is a non-steroidal anti-inflammatory drug sparingly soluble in water. It is weakly acidic (pKa ≈ 6.5) because of its methanesulfonamide functional group. The pKa of captopril was determined by potentiometric titration with NaOH 2.0 x 10-2 moL L ¹. The pKa of nimesulide was determined by using spectrophotometry and photometric titration. The experimental values of pKa of both drugs are in very good agreement with those from literature

Síntese e hidrólise de azalactonas de Erlenmeyer-Plöchl mediadas por radiação micro-ondas em aparelhos doméstico e dedicado: experimentos de química orgânica para a graduação

This work describes a green chemistry experiment for the synthesis of Erlenmeyer-Plöchl azalactones mediated by microwave irradiation, employing both dedicated and domestic equipment. Hippuric acid was reacted with equimolar amounts of benzaldehyde, p-chloro-benzaldehyde or p-N,N-dimethyl-benzaldehyde in acetic anhydride as the solvent. Acid hydrolysis of obtained 4-benzylidene-2-phenyloxazol-5(4H)-one under microwave and convectional heating afforded Z-α-(benzoylamino)cinnamic acid at a 51-61.5% yield. The UV-Vis molecular spectra of 4-benzylidene-2-phenyloxazol-5(4H)-one and 4-(4'-N,N-dimethylbenzylidene)-2-phenyloxazol-5(4H)-one were obtained in ethanol, CH2Cl2 and DMSO and bathochromic shift was observed for the latter azalactone.