Kinetic modeling of the simultaneous production of ethanol and fructose by Saccharomyces cerevisiae

Background: Ethanol and fructose are two important industrial products that enjoy many uses. In this contribution, their production via selective fermentation of date extract using Saccharomyces cerevisiae was studied. Scaling up the process for possible commercialization was investigated in three fermentors with working volume ratio of 1:40:400. Results: Higher ethanol concentration was obtained in the larger fermentor due to conversion of fructose. Fructose yields in the 0.5-L, 7.5-L and 80-L fermentors were 99, 92 and 90%, respectively. Good fitting was obtained with the modified Monod kinetics; however, a better fit of cell mass was obtained with the modified Ghose­Tyagi model which accounts for ethanol inhibition. Conclusions: The modified Gompertz model was expanded to facilitate prediction of products' formation and fructose fractions in all three fermentors. Such expansion will be beneficial in industrial applications.

Growth Kinetic Profile of Candida albicans Under Varying Environmental Conditions

Several environmental conditions were identified to influence the growth and morphogenesis of Candida albicans. The present study quantitatively examined the growth rate and described the kinetic profile of C. albicans under different pH, temperature, and culture medium. When C. albicans was monitored over the 12-h period under different culture media, temperature values, and pH levels, the growth kinetic profile of the organism behaved in accordance with the first-order rate equation. The organism exhibited a relatively faster growth rate when incubated at 37ºC in modified Sabouraud glucose broth medium with pH 7.4. Moreover, the growth profile exhibited a linear pattern between 1.5 h and 6 h after inoculation of C. albicans culture which coincides with the mycelium production, and subsequently shifted to an exponential increase beyond 6 h. Given the environmental conditions selectively supporting the growth and morphogenesis of C. albicans, quantitative descriptions of the rate kinetic profile of C. albicans population offer an objective approach in comparing environmental conditions with varying physicochemical characteristics and biochemical compositions.

Formulation and in-vitro bioequivalence evaluation of verapamil hydrochloride matrix tablets with Calan SR.

The purpose of the current work was to formulate Verapamil Hydrochloride (VH) sustained release matrix tablets by using natural polymers and comparison with leading national brand Calan SR of Searle Pharmaceuticals. Tragacanth and pectin were used in various concentrations. Pre compression studies i.e. angle of repose, bulk density, tapped density, Carr’s compressibility index and Hausner’s ratio were also performed and found within the Pharmacopoeial limits. Eight formulations (F1-F8) of (VH) were prepared by direct compression method. Post compression studies i.e. Thickness, Hardness, Diameter, Friability and Dissolution studies were conducted. Different kinetic models i.e. zero order, first order, Highuchi model and Korsmeyer Peppas were applied to study release patterns and similarity index was calculated. Dissolution studies were carried out in phosphate buffer of pH 6.8 showed that formulations (F4 and F8) formulated with higher polymers concentration showed comparatively better drug retardation. F5 was the most comparable with the reference product. Verapamil hydrochloride released was observed non-fickian as diffusion following Higuchi model.

Formulation and in-vitro bioequivalence evaluation of verapamil hydrochloride matrix tablets with Calan R.

The purpose of the current work was to formulate Verapamil Hydrochloride (VH) sustained release matrix tablets by using natural polymers and comparison with leading national brand Calan SR of Searle Pharmaceuticals. Tragacanth and pectin were used in various concentrations. Pre compression studies i.e. angle of repose, bulk density, tapped density, Carr’s compressibility index and Hausner’s ratio were also performed and found within the Pharmacopoeial limits. Eight formulations (F1-F8) of (VH) were prepared by direct compression method. Post compression studies i.e. Thickness, Hardness, Diameter, Friability and Dissolution studies were conducted. Different kinetic models i.e. zero order, first order, Highuchi model and Korsmeyer Peppas were applied to study release patterns and similarity index was calculated. Dissolution studies were carried out in phosphate buffer of pH 6.8 showed that formulations (F4 and F8) formulated with higher polymers concentration showed comparatively better drug retardation. F5 was the most comparable with the reference product. Verapamil hydrochloride released was observed non-fickian as diffusion following Higuchi model.

Adsorption of Copper (II) Ions from Aqueous Solution onto Synthetic Goethite and Two Naturally Available Red Soils from Yaoundé –Cameroon.

The present investigation deals with the utilization of synthetic goethite and two red soils obtained from AHALA-NSAM and NKOLOFANE as adsorbent for the removal of copper from waste water. The synthetic goethite was characterized by IR, XRD and BET where the red soils were characterized by XRD, Chemical Analysis and BET. A series of experiments were conducted in a batch system to evaluate the effect of system variables. The effect of contact time, pH and the initial concentration of copper (II) solution were considered. The results show that the contact time of 180 minutes, 20 minutes and 15 minutes are sufficient to fit the equilibrium for GEO, E1-B1 and NSAM-B2 respectively. The optimal adsorption pH for the adsorption of copper (II) ions is 4.6±1. The maximal quantities adsorbed by every adsorbent were 78 .2 mg/g for GEO, 41.2mg/g for E1-B1 and 32.2mg/g for NSAM-B2. The experimental results obtained have been correlated to four kinetic models including the first order, the second order, Elovich and intra particle diffusion models. The kinetic model that gave the value of the linear correlation coefficient which best fits is that of second order. Three isotherms models amongst which are Langmuir, Freundlich and Tempkin’s have been applied to the experimental data. The Langmuir model best described the adsorption of copper (II) ions in aqueous solution by the three adsorbents.

Hidrólisis enzimática de residuos de la cosecha de caña de azúcar / Hydrolysis Enzymatic of crop residues sugar cane

En esta investigación, se hidrolizó un sustrato deslignificado proveniente de residuos de la cosecha caña de azúcar (hojas y cogollos) usando un preparado enzimático con 27.53 unidades de papel filtro (FPU), obtenido a partir de enzimas comerciales. La hidrólisis se llevó a cabo a un pH de 4.2 y una temperatura de 50 oC. Fueron analizados modelos de inhibición por sustrato, glucosa e inhibición total por producto. Los resultados mostraron que los modelos que mejor se ajustan a los datos experimentales, son los modelos de inhibición competitiva por glucosa, con una constante de Michaelis (Km) de 20.37 g/L, velocidad máxima (Vmax) 39 g/L h y una constante de inhibición (ki) de 0.442. En el caso que las relaciones enzima – Sustrato (E/S) sean mayores de 0.5, se puede aplicar el modelo cinático de Michaelis-Menten.

In this research, a delignified substrate from crops residues sugar cane residues (leaves and top cane) was hydrolyzed using an enzyme preparation with 27.53 FPU. This enzyme was obtained from trade. Hydrolysis was carried out to pH of 4.2 and a temperature of 50 oC. Models of inhibition models substrate, glucose and total inhibition product was analyzed. The results showed that models that best fit the data experimental was the models competitive glucose inhibition (Km= 20.37, Vmax=39 and ki= 0.442). In the event that E/S is above 0.5, can applied kinetic models of Michaelis – Menten.

Recovery of phytase produced by solid-state fermentation on citrus peel

The extraction of phytase produced by solid-state fermentation of citrus peel was studied employing a multistage leaching process. It was observed that the extracts containing EDTA retained over 90 percent of phytase activity at room temperature after 24 h after the leaching. A fractional design 2² (with 4 replicates at the central point) was carried out for testing the pH and agitation as process independent factors. Only the interaction between the pH and agitation showed a significant influence. These factors were optimized with a central composite design. Agitation at 300 rpm and pH at 5.0 were the best conditions to extract the enzyme from solid matrix. The modeling of the process indicated that diffusivity of the enzyme in the solvent was the controlling mechanism. The corresponding kinetic constant and saturation concentration in this process were 0.89 min-1 and 4.0 IU/mL, respectively. The multistage process indicated that after two steps, it was possible to recover 85 percent of total enzyme produced.

A extração de fitases produzidas por fermentação em estado sólido de polpa cítrica foi estudada utilizando um processo de extração sólido-líquido em varias etapas. A adição de EDTA permite manter durante 24 horas a temperatura ambiente 90 por cento da atividade inicial do caldo com a enzima extraída. Um planejamento fatorial 2², com 4 replicas no ponto central, foi desenvolvido para testar os valores de ph e agitação convenientes para a extração das enzimas. A interação entre ambos os fatores foi estadisticamente significativa. A atividade da enzima foi otimizada nos valores onde o pH (5.0) e a agitação (350 rpm) resultaram ser as melhores condições para extrair a enzima da matriz sólida. O ajuste do modelo matemático obtido mostra que é possível considerar a difusividade como o mecanismo que controla o processo de transferência de massa. A constante cinética que descreve este processo e a concentração de saturação foram 0.039 min-1 e 4.01 IU/mL respectivamente. A extração em varias etapas mostrou que nas duas primeiras etapas é possível recuperar 85 por cento da fitase produzida.

Kinetic analysis and effect of culture medium and coating materials during free and immobilized cell cultures of Bifidobacterium animalis subsp. lactis Bb 12

Microencapsulation technique appears helpful for more protection of Bifidobacteria against acid inhibitory effect. The effect of medium composition and product inhibitory in free cell culture, as well as the effect of the coating materials in immobilized cells, on biomass growth, acid production and substrate utilization kinetics of Bifidobacterium animalis subsp. lactis Bb 12 in uncontrolled batch fermentation was examined. The Monod and the Luedeking and Piret equations with a product inhibition term involving toxic power terms improved model efficiency for both growth and production. The model showed that media and coating materials had an effect on toxic power terms. Cell immobilization had a positive impact on B. animalis culture. Kinetic analysis revealed the permeability of the coating material had a major impact on culture parameters; permeability increased in the following way: Gellan xanthan < Alginate chitosan < K-Carageenan-locust been, and hence growth parameters x m, maximum specific growth rate (h-1) (um) and monod constant (g lactose L-1) (K S) followed the same trend as well as the linking between growth and production. The link between the microbial environment and cell growth was highlighted by the model. It was shown that for an increasing protect effect of coating materials against environmental deleterious factors, namely a decrease of the permeability, transport limitation occurred, which was disadvantageous for cell formation.