DSpace Angular :: Browsing by Author "Agosin, E"

Browsing by Author "Agosin, E"

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A neural network estimator for total biomass of filamentous fungi growing on two dimensional solid substrate
(KLUWER ACADEMIC PUBL, 1998) Acuna, G; Giral, R; Agosin, E; Jorquera, H; Perez Correa, R; Ferret, E; Molin, P; Thibault, J
A neural network dynamic model is proposed for the on-line estimation of total biomass during filamentous fungi cultures on two dimensional solid substrate. The neural network provides an accurate and robust estimation of biomass from macroscopic measurements of the colony radius evolution. Experiments were performed on Gibberella fujikuroi growing on Petri dishes under different conditions of temperature and water activity.
Biomass content governs fermentation rate in nitrogen-deficient wine musts
(AMER SOC MICROBIOLOGY, 2004) Varela, C; Pizarro, F; Agosin, E
Problematic fermentations are common in the wine industry. Assimilable nitrogen deficiency is the most prevalent cause of sluggish fermentations and can reduce fermentation rates significantly. A lack of nitrogen diminishes a yeast's metabolic activity, as well as the biomass yield, although it has not been clear which of these two interdependent factors is more significant in sluggish fermentations. Under winemaking conditions with different initial nitrogen concentrations, metabolic flux analysis was used to isolate the effects. We quantified yeast physiology and identified key metabolic fluxes. We also performed cell concentration experiments to establish how biomass yield affects the fermentation rate. Intracellular analysis showed that trehalose accumulation, which is highly correlated with ethanol production, could be responsible for sustaining cell viability in nitrogen-poor musts independent of the initial assimilable nitrogen content. Other than the higher initial maintenance costs in sluggish fermentations, the main difference between normal and sluggish fermentations was that the metabolic flux distributions in nitrogen-deficient cultures revealed that the specific sugar uptake rate was substantially lower. The results of cell concentration experiments, however, showed that in spite of lower sugar uptake, adding biomass from sluggish cultures not only reduced the time to finish a problematic fermentation but also was less likely to affect the quality of the resulting wine as it did not alter the chemistry of the must.
Chemical markers for tracking the sensory contribution of production stages in muscat wine distillates
(WILEY, 2005) Lillo, MPY; Agosin, E; Latrille, E
The main sensory contribution of each post-fermentation production stage of muscat wine distillates can be tracked by following the concentration of just 1 corresponding chemical marker. Matching sample clusters of sensory and chemical data by using principal components analysis (PCA) revealed potential chemical markers. The data used in this study correspond to 12 sensory attributes that showed significant differences among products (P < 0.05) and concentrations of 23 volatile compounds of 14 distillate fractions and 15 finished. Piscos. Artificial fruit attribute, characteristic of the head fraction (FR1) can be tracked with esters. Linalool, main odor attribute of the 1st part of the heart (FR2) can be tracked with linalool molecule. The 2nd part of the heart (FR3) can be tracked with octanoic acid, decanoic acid, furfural and ethyl lactate, accounting for tails attribute. In blended and aged finished products, chemical markers accounting for the effects of distillate fractions were similar but not identical to the markers from samples obtained from the purely distilled samples. Chemical markers for FR1 are ethyl hexanoate, ethyl octanoate, ethyl decanoate. Differentiation between FR1 and FR2 is less evident than in the purely distilled samples due to the linalool and artificial fruit attribute correlation. Chemical markers for FR2, therefore, include linalool and esters ethyl hexanoate, ethyl octanoate, and ethyl decanoate. The blending of the 2nd, part of the heart (FR3) can be tracked with 2-phenylethanol, ethyl lactate, and decanoic acid. Oak aging was tracked with eugenol and whisky lactones, while 5-hydroxy-methyl-2-furfural accounted for added caramel.
Comparison between odour and aroma profiles of Chilean Pisco spirit
(ELSEVIER SCI LTD, 2005) Lillo, MPY; Latrille, E; Casaubon, G; Agosin, E; Bordeu, E; Martin, N
Precise sensory measurements of odour (orthonasal) and aroma (retronasal olfactory perception) are time and resource consuming. The aim of this work was to develop improved olfactory tasting procedures. Odour and aroma profiles of 13 Pisco spirits and 14 distillation fractions were obtained through descriptive analysis by a panel of 12 trained subjects. The samples were discriminated by 12 odour and 11 aroma attributes out of 13, with odour being slightly more discriminant at a panel and individual level. Samples were differentiated according to the type of distillation fraction and maturation process. None of the tasting modes induced significantly higher intensity judgement, with the exception of linalol whose average sample odour intensity was higher. However, there were differences in intensity scores between modes due to subject-mode interactions for all attributes except linalol and, to a lesser extent, to product-mode interactions for tails, ethyl acetate and linalol. Partial least square (PLS) models gave a good prediction of aroma from odour scores, except for oak attribute which exhibited a non-linear behaviour. Overall, Pisco olfactory perception can be limited to odour assessment. (C) 2004 Elsevier Ltd. All rights reserved.
Control strategies for intermittently mixed, forcefully aerated solid-state fermentation bioreactors based on the analysis of a distributed parameter model
(PERGAMON-ELSEVIER SCIENCE LTD, 2004) von Meien, OF; Luz, LFL; Mitchell, DA; Perez Correa, JR; Agosin, E; Fernandez Fernandez, M; Arcas, JA
This paper tests different control strategies based on classic proportional integral derivative (PID) and advanced dynamic matrix control (DMC) algorithms for an intermittently stirred, forcefully aerated solid-state fermentation bioreactor. The study was done using a distributed parameter model to reproduce the main operating features of this type of bioreactor. There is predicted to be a remarkable improvement in the bioreactor productivity when control strategies are implemented. For this type of bioreactor, the temperature and water content of the substrate bed can be controlled by saturating the air at the air inlet but manipulating its temperature, coupled with a strategy of water replenishment when the water content of the bed falls below a threshold. Dynamic matrix control is superior to PID control; however, a specific convolution matrix for different stages of the fermentation is necessary due to the changing behavior of the system. This work shows the benefit of mathematical modeling, since the many different operating conditions investigated via simulations would not have been economically feasible to undertake experimentally with a large-scale bioreactor. The results obtained provide an excellent starting point for such large-scale experimental work. (C) 2004 Elsevier Ltd. All rights reserved.
Effect of water activity on gibberellic acid production by Gibberella fujikuroi under solid-state fermentation conditions
(ELSEVIER SCI LTD, 2005) Corona, A; Saez, D; Agosin, E
The evolution of water activity during solid-state cultivation of Gibberella fujikuroi was followed. A typical organic substrate, wheat bran and soluble starch, was used. Culture sorption isotherms were determined verifying that, as culture evolves, higher moisture contents were necessary to maintain the same water activity level. Optimal values for Gibberella fujikuroi growth and gibberellic acid production rates and yields were established, around a(w) 0.99. A non-linear model, based on neural networks, is proposed to represent the sorption curves of the substrate during the fermentation process. (c) 2005 Elsevier Ltd. All rights reserved.
Effectiveness of conidia of Trichoderma harzianum produced by liquid fermentation against Botrytis bunch rot of table grape in Chile
(ELSEVIER SCI LTD, 1997) Latorre, BA; Agosin, E; SanMartin, R; Vasquez, GS
Over 100 isolates of Trichoderma harzianum Rifai were obtained from soil samples and from the phylloplane of kiwifruit (Actinidia chinensis Planchon), grape (Vitis vinifera), orange (Citrus sinensis (L.) Osbeck), eucalyptus (Eucalyptus globulus Labill.), and apricot (Prunus armeniaca L.) in Chile. A subsample of 48 isolates were tested and found to be antagonistic to Botrytis cinerea Pers. ex Fr. on apple fruits. Isolate S10B from soil in Chile provided similar control of Botrytis bunch rot under field conditions to reference isolate P1 (ATCC 74058) and T39 (Trichodex 25 WP). However, field trials conducted during four growing seasons (1992-1995) with preparations of conidia of formulated or non-formulated T. harzianum P1 provided only partial control of Botrytis bunch rot of 'Thomson Seedless' table grape. Disease incidence was significantly different (p < 0.05) from untreated controls, but equal to or less than the control achieved with vinclozolin (Ronilan 50 WP, 1.5 kg ha(-1)) and similar to captan (Captan 80 WP, 4 kg ha(-1)). This level of control is insufficient considering that tolerance for B. cinerea is very low (< 0.5%) on table grapes. Nevertheless, the antagonistic activity of T. harzianum may be effective if it is integrated with other control practices, and may result in acceptable levels of disease control with reduced levels of pesticide use. (C) 1997 Elsevier Science Ltd.
Heterologous expression of Escherichia coli ppsA (phosphoenolpyruvate synthetase) and galU (UDP-glucose pyrophosphorylase) genes in Corynebacterium glutamicum, and its impact on trehalose synthesis
(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2005) Padilla, L; Agosin, E
Trehalose is a disaccharide with a wide range of applications in the food industry. We recently proposed a strategy for trehalose production based on a Corynebacterium glutamicum strain expressing the Escherichia coli enzyme UDP-glucose pyrophosphorylase (GalU).
Impact of heterologous expression of Escherichia coli UDP-glucose pyrophosphorylase on trehalose and glycogen synthesis in Corynebacterium glutamicum
(AMER SOC MICROBIOLOGY, 2004) Padilla, L; Morbach, S; Kramer, R; Agosin, E
Trehalose is a disaccharide with a wide range of applications in the food industry. We recently proposed a strategy for trehalose production based on improved strains of the gram-positive bacterium Corynebacterium glutamicum. This microorganism synthesizes trehalose through two major pathways, OtsBA and TreYZ, by using UDP-glucose and ADP-glucose, respectively, as the glucosyl donors. In this paper we describe improvement of the UDP-glucose supply through heterologous expression in C. glutamicum of the UDP-glucose pyrophosphorylase gene from Escherichia coli, either expressed alone or coexpressed with the E. coli ots genes (galU otsBA synthetic operon). The impact of such expression on trehalose accumulation and excretion, glycogen accumulation, and the growth pattern of new recombinant strains is described. Expression of the galU otsBA synthetic operon resulted in a sixfold increase in the accumulated and excreted trehalose relative to that in a wild-type strain. Surprisingly, single expression of galU also resulted in an increase in the accumulated trehalose. This increase in trehalose synthesis was abolished upon deletion of the TreYZ pathway. These results proved that UDP-glucose has an important role not only in the OtsBA pathway but also in the TreYZ pathway.
Indirect measurement of water content in an aseptic solid substrate cultivation pilot-scale bioreactor
(JOHN WILEY & SONS INC, 2001) Lillo, MPY; Perez Correa, R; Agosin, E; Latrille, E
A lack of models and sensors for describing and monitoring large-scale solid substrate cultivation (SSC) bioreactors has hampered industrial development and application of this type of process. This study presents an indirect dynamic measurement model for a 200-kg-capacity fixed-bed SSC bioreactor under periodic agitation. Growth of the filamentous fungus Gibberella fujikuroi on wheat bran was used as a case study. Real data were preprocessed using previously reported methodology. The model uses CO, production rate and inlet air conditions to estimate average bed water content and average bed temperature. The model adequately reproduces the evolution of the average bed water content and can therefore be used as an on-line estimator in pilot-scale SSC bioreactors. To obtain a reasonable fit of the bed temperature, however, inlet air humidity measurements will have to be adjusted with a data reconciliation algorithm. Good estimation of temperature is important for the future design of improved water content estimation using state observers. The model also provides insight into understanding the complex behavior of the dynamic system, which could prove useful when establishing advanced model-based operational and control strategies. (C) 2001 John Wiley & Sons, Inc.
Influence of a mixed culture with Debaryomyces vanriji and Saccharomyces cerevisiae on the volatiles of a Muscat wine
(INST FOOD TECHNOLOGISTS, 2002) Garcia, A; Carcel, C; Dulau, L; Samson, A; Aguera, E; Agosin, E; Gunata, Z
A non-Saccharomyces yeast strain, Debaryomyces vanriji, isolated from grape berry flora was found to Influence wine volatiles of the cv. Muscat of Frontignan when co-cultured with native or inoculated with a selected strain of Saccharomyces cerevisiae during fermentation. The concentrations of several volatiles were significantly different (p < 0.05) between the control and the 2 wines inoculated with D. vanriji. The latter were richer in fatty acids, esters, and terpenols. The increase in geraniol concentration In D. vanriji wines could be attributed to the hydrolysis of the corresponding glucosidic precursor by D. vanriji β-glucosidase. D. vanriji inoculated musts showed higher levels of β-glucosidase activity through fermentation compared to the control sample.
Influence of sun exposure on the aromatic composition of Chilean Muscat grape cultivars Moscatel de Alejandria and Moscatel rosada
(AMER SOC ENOLOGY VITICULTURE, 1997) Belancic, A; Agosin, E; Ibacache, A; Bordeu, E; Baumes, R; Razungles, A; Bayonove, C
The effect of sun exposure on the aromatic composition of two Muscat grape cultivars, Moscatel de Alejandria and Moscatel rosada, was monitored over two seasons. Fully exposed and artificially shaded clusters permitting 20% (shaded) and 50% (semi-shaded) sun exposure were used to assess the impact of shading in fruit aroma composition. Both cultivars contained similar levels of total free terpenols (2100 mu g/L), although Moscatel de Alejandria was richer in total bound terpenols. The highest concentration of free terpenols was obtained from the semi-shaded treatment, although for Moscatel de Alejandria, the resulting difference between exposed and semi-shaded treated grapes was negligible. Shaded grapes had the lowest concentration of terpenols, with poor Muscat typicity. The content of one of the most important terpenols from the aromatic perspective, linalool, appeared to be the most sensitive to sun exposure. Berry temperature appeared to be critical for maximizing monoterpene levels and muscat flavor in the fruit.
Metabolic engineering of Corynebacterium glutamicum for trehalose overproduction: Role of the TreYZ trehalose biosynthetic pathway
(AMER SOC MICROBIOLOGY, 2006) Carpinelli, J; Kramer, R; Agosin, E
Trehalose has many potential applications in biotechnology and the food industry due to its protective effect against environmental stress. Our work explores microbiological production methods based on the capacity of Corynebacterium glutainicum to excrete trehalose. We address here raising trehalose productivity through homologous overexpression of maltooligosyltrehalose synthase and the maltooligosyltrehallose trehalohydrolase genes. In addition, heterologous expression of the UDP-glucose pyrophosphorylase gene from Escherichia coli improved the supply of glycogen. Gene expression effects were tested on enzymatic activities and intracellular glycogen content, as well as on accumulated and excreted trehalose. Overexpression of the treY gene and the treY/treZ synthetic operon significantly increased maltooligosyltrehalose synthase activity, the rate-limiting step, and improved the specific productivity and the final titer of trehalose. Furthermore, a strong decrease was noted in glycogen accumulation. Expression of galU/treY and galU/treYZ synthetic operons showed a partial recovery in the intracellular glycogen levels and a significant improvement in both intra- and extracellular trehalose content.
Modeling of yeast metabolism and process dynamics in batch fermentation
(JOHN WILEY & SONS INC, 2003) Sainz, J; Pizarro, F; Perez Correa, JR; Agosin, E
Much is known about yeast metabolism and the kinetics of industrial batch fermentation processes. In this study, however, we provide the first tool to evaluate the dynamic interaction that exists between them. A stoichiometric model, using wine fermentation as a case study, was constructed to simulate batch cultures of Saccharomyces cerevisiae. Five differential equations describe the evolution of the main metabolites and biomass in the fermentation tank, while a set of underdetermined linear algebraic equations models the pseudo-steady-state microbial metabolism. Specific links between process variables and the reaction rates of metabolic pathways represent microorganism adaptation to environmental changes in the culture. Adaptation requirements to changes in the environment, optimal growth, and homeostasis were set as the physiological objectives. A linear programming routine was used to define optimal metabolic mass flux distribution at each instant throughout the process. The kinetics of the process arise from the dynamic interaction between the environment and metabolic flux distribution. The model assessed the effect of nitrogen starvation and ethanol toxicity in wine fermentation and it was able to simulate fermentation profiles qualitatively, while experimental fermentation yields were reproduced successfully as well. (C) 2003 Wiley Periodicals, Inc.
Modelling Gibberella fujikuroi growth and GA(3) production in solid-state fermentation
(ELSEVIER SCI LTD, 2002) Gelmi, C; Perez Correa, R; Agosin, E
A simple differential equation model was developed to represent the growth and production of a secondary metabolite in solid-state cultivation (SSC) under conditions of limited nitrogen. The model was used to interpret data obtained from SSCs of the fungus Gibberella fujikuroi, under different temperatures (25 and 31 degreesC) and water activity conditions (0.985, 0.992, 0.999). The model was calibrated in two steps. An innovative procedure to achieve good initial guesses for key parameters, such as maintenance coefficients and death rates was first applied. These initial guesses were then used in a non-linear optimisation routine to get a minimum least squares fit for the model. The mathematical model was able to reproduce the measured variables: biomass, urea, starch, CO2, O-2 and GA(3) satisfactorily. Moreover. the model indicated that the fungus does not assimilate the nitrogen source, urea, directly. The model will be useful in developing optimal feeding policies and on-line biomass estimators. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.
Monitoring large scale wine fermentations with infrared spectroscopy
(ELSEVIER, 2004) Urtubia, A; Perez Correa, JR; Meurens, M; Agosin, E
Negative effects on wine quality and productivity caused by stuck and sluggish fermentations can be reduced significantly, if such problems are detected early through periodic chemical analysis. Infrared spectroscopy (IR) has been used successfully for monitoring fermentations, since many compounds can be measured quickly from a single sample without prior treatment. Nevertheless, few applications of this technology in large scale winemaking have been reported, and these do not cover the entire fermentation from must to finished wine. In this work, we developed IR calibrations for analyzing the fermenting must at any stage of fermentation. The calibration model was obtained with multivariable partial least squares and proved effective for analyzing Cabernet Sauvignon fermentations for glucose, fructose, glycerol, ethanol, and the organic acids; malic, tartaric, succinic, lactic, acetic, and citric. Upon external validation we found an average relative predictive error of 4.8%. Malic acid showed the largest relative predictive error (8.7%). In addition, external validation found that insufficient data for these calibrations made the analysis of fermenting musts using other grape varieties less reliable. (C) 2004 Elsevier B.V. All rights reserved.
Proposal for a standardized set of sensory terms for pisco, a young muscat wine distillate
(AMER SOC ENOLOGY VITICULTURE, 2004) Bordeu, E; Formas, G; Agosin, E
The predominantly muscat aroma of pisco, a young distillate produced in northern Chile and Peru, distinguishes it from other young spirits. Standardized terminology is necessary, however, to describe differences among the wide range of piscos. This is the first proposal for a standardized set of descriptive terminology for this type of product. A panel of trained specialists established the proposed terminology, which is displayed in a wheel format and in a list of corresponding standards.
Reassessment of the estimation of dissolved oxygen concentration profile and K(L)a in solid-state fermentation
(ELSEVIER SCI LTD, 2000) Thibault, J; Pouliot, K; Agosin, E; Perez Correa, R
Oxygen mass transfer in aerobic microbial growth systems is often a limiting factor for optimal growth and productivity. Oxygen mass transfer has been widely studied in submerged fermentations but has attracted as yet little attention for solid state fermentations. The parallel to submerged fermentation has led to the incorrect interpretation and use of the overall oxygen mass transfer coefficient (K(L)a) to assess the ability of a particular fermentation system to supply the oxygen to microorganisms. The use of K(L)a, as traditionally defined, should be used with caution in solid substrate fermentation systems because there is no convection on the liquid side of the medium, and oxygen is consumed in the biofilm. Hence, K(L)a must be redefined for solid state fermentation. In this payer, the use of oxygen mass transfer coefficients in solid state fermentations is clarified. Published literature data were analysed with a simple pseudo-steady-state model and used to discuss the influence of the biofilm thickness, the dissolved oxygen diffusion coefficient, the convective gas mass transfer coefficient, and the gas flow rate on the oxygen mass transfer coefficient in solid state fermentations. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.
Rigorous dynamic modeling and simulation of wine distillations
(ELSEVIER SCI LTD, 2004) Osorio, D; Perez Correa, R; Belancic, A; Agosin, E
A novel simulation strategy for dynamic distillation of complex mixtures, such as wine, is proposed and evaluated in terms of computing efficiency and accuracy. The model developed describes wine distillation as a multicomponent reactive batch distillation process. The simulation approach transforms the system of differential algebraic equations (DAE) into a set of ordinary differential equations, by pre-solving the algebraic equations and replacing them with artificial neural networks.
Solid substrate cultivation of Gibberella fujikuroi on an inert support
(ELSEVIER SCI LTD, 2000) Gelmi, C; Perez Correa, R; Gonzalez, M; Agosin, E
Growth of Gibberella fujikuroi on Amberlite, an inert support, and gibberellic acid (GA,) production was studied in glass columns under different conditions of temperature and water activity (a(w)). Maximum biomass concentration and GA(3) production were respectively 40 (mg/g inert support) and 0.73 (mg/g inert support). While high specific growth rates were obtained, low initial nitrogen resulted in low biomass concentrations. Maximum GA(3) (31 degrees C, a(w)=0.985) was not produced by the maximum concentration of biomass (25 degrees C, a(w)=0.992). Peaks in the rate curves of either outlet gas, CO2 or O-2 occurred on exhaustion of urea indicating, for future works, just when to feed the culture additional nitrogen. (C) 2000 Elsevier Science Ltd. All rights reserved.

Browsing by Author "Agosin, E"

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