Abstract
The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come ...mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, strongest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, particularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent.
For any given large-scale solid substrate fermentation (SSF) bioreactor, to assess how well a control system will work in practice requires the most realistic model possible. This model needs to ...account fully for complicated dynamic reactor behaviour and, in addition, has to include a specific noise model that is capable of reproducing the disturbances observed in SSF bioreactor measurements. In this work, noisy data collected historically from SSF pilot scale fermentations was used to develop such a model. Applying standard signal processing techniques, each measured variable was separated into deterministic and noise signals. Deterministic signals were used to calibrate a previously developed phenomenological model of the bioreactor. Noise signals were used to construct a realistic noise model for each measured variable in turn. Finally, the two models were combined to attain simulations that compared well with real measurements. This integrated model will provide realistic simulations that will prove useful in the design of effective control systems for intermittently mixed SSF bioreactors.
Recent years have witnessed a surge in research in cellular biology. There has been particular interest in the interaction between cellular metabolism and its environment. In this work we present a ...framework for fitting fermentation models that include this interaction. Differential equations describe the evolution of extracellular metabolites, while a Linear Program (LP) models cell metabolism, and piecewise smooth functions model the links between cell metabolism and its environment. We show that the fermentation dynamics can be described using Differential Variational Inequalities (DVIs). Discretization of the system and reformulation of the VIs using optimality conditions converts the DVI to a Mathematical Program with Complementarity Constraints (MPCC). We briefly describe an interior point algorithm for solving MPCCs. Encouraging numerical results are presented in estimating model parameters to fit model prediction and data obtained from fermentation, using cultures of Saccharomyces cerevisiae reported in the literature. PUBLICATION ABSTRACT
Direct monitoring of bed conditions in large scale solid-state fermentation (SSF) bioreactors is difficult due to lack of reliable and affordable instrumentation. Although, relevant variables such as ...average bed temperature and water content can be inferred from energy and water balances, these estimations are prone to significant error since the process is complex and measured variables are extremely noisy. Hence, to obtain better estimation of bed conditions, simple and robust models, and effective noise suppression methods should be developed. A kinetic model was applied to obtain noise free CO
2 production rate (
CPR) values, which in turn was used in water and energy balances. The evolution of other relevant variables including total and active biomass, O
2 consumption rate, secondary metabolite production and dry mass degradation were also calculated. The proposed model was calibrated with data obtained in an agitated aseptic SSF pilot-scale bioreactor of 200
kg, growing
Gibberella fujikuroi on wheat bran and starch. The calibration was achieved by means of a non-linear optimization routine. With this model better average bed temperature estimates, compared with a model that uses noisy (
CPR) measurements, were attained. Hence, the proposed model can be used on-line to estimate more reliable average bed conditions and to develop model based control strategies. In addition, a predictive model for bioreactor design can be derived from the proposed model, after good outlet gas temperature estimation has been achieved.
An efficient macroporous resin purification process was designed to obtain food-grade phlorotannin-rich extracts from the seaweeds Durvillaea incurvata and Lessonia spicata. Phlorotannins were ...profiled to relate structures with the α-glucosidase inhibitory activity of the extracts. Liquid chromatography-mass spectrometry was applied for tentative identification. The best phlorotannin purification performance was achieved with HP-20 resin and elution with 80% v/v ethanol. This is the first study that demonstrates the effectivity of HP-20 resin for removing potentially toxic elements (As, Cd) from seaweed extracts. Fucols/phlorethols/fucophlorethols isomers up to 4 phloroglucinol units (PGU) were the most representative phlorotannins. High molecular weight species (11-21 PGU), although in low abundances, were detected in D. incurvata for the first time. Eckols, carmalols, fuhalols, phenolic acids, and flavonoids were also detected. Some extracts' potent α-glucosidase inhibitory activities were related to their high phlorotannin abundances, the presence of phlorotannins of a high degree of polymerization, and the phlorotannins class.
Industrial automation is useful to reduce production costs and improve product quality. The wine industry has been increasingly adopting industrial automation seeking these objectives. In Chile, ...wineries have been lagging behind in embracing new technologies to control the fermentation process. In most cases, enologists decide control actions (cooling, heating, pumping over) based on off line periodic measurements. In this work we explore the applicability of ultrasound to measure the sugar and alcohol concentrations of hydroalcoholic solutions mimicking fermenting musts. Additionally, implementation issues such as the attenuation effect of bubbles and tank curvature are analyzed. We show that working at two sufficiently distinct frequencies, we can measure sugar and alcohol content simultaneously. Measurement resolution achieved for the wave time of travel translates to a better than 0.02% for both concentrations, depending on the container size.
The effect of body condition score (BCS) on estrus characteristics and ovarian function was evaluated in 44 synchronized Beef-Master cows. Weaned adult cows in anestrous were grouped according to ...their BCS as BCS1-2 (n = 13), BCS3-4 (n = 17) and BCS5-6 (n = 14). All cows were synchronized using norgestomet implants plus estradiol valerate for 9 days. The estrus detection began 24 hours after implant removal and it was detected every 6 hours for 72 hours. The time from implant removal to the onset of estrus (TIR) and the duration of estrus were registered. All animals were examined 4 times with a transrectal ultrasound kit to determine the size of the follicles (6 to 9 mm or > 9 mm), the diameter of the largest follicle (DLF), ovulation rate, ovulation rate relative to estrus detection (ORE) and ovulation rate relative to the follicle size (ORF). The effect of BCS on TIR, the duration of the estrus, the number of follicles of size 6 to 9 mm or > 9 mm, and DLF was determined using analysis of variance. The effect of BCS on ovulation rate, ORE and ORF, were analyzed using Chi-square tests. There were no differences (P> 0.05) between TIR, duration of estrus and follicle sizes between BCS groups. The DLF increased from 9.8 to 12.9 mm, the OR increased from 7.7 to 85.7%, the ORE from 0 to 100% and the ORF from 16.7 to 92.9%. In conclusion, under the range of BCS of the synchronized cows evaluated in this study, the BCS of Beef Master cows did not affect the estrus traits; which agree with results observed in other breeds of cattle in the tropics. However, body condition affects follicle development and ovulation rate.
Calibration of mechanistic kinetic models describing microorganism
growth and secondary metabolite production on solid substrates is
difficult due to model complexity given the sheer number of ...parameters
needing to be estimated and violation of standard conditions of
numerical regularity. We show how advanced non-linear programming
techniques can be applied to achieve fast and reliable calibration of a
complex kinetic model describing growth of Gibberella fujikuroi and
production of gibberellic acid on an inert solid support in glass
columns. Experimental culture data was obtained under different
temperature and water activity conditions. Model differential equations
were discretized using orthogonal collocations on finite elements while
model calibration was formulated as a simultaneous
solution/optimization problem. A special purpose optimization code
(IPOPT) was used to solve the resulting large-scale non-linear program.
Convergence proved much faster and a better fitting model was achieved
in comparison with the standard sequential solution/optimization
approach. Furthermore, statistical analysis showed that most parameter
estimates were reliable and accurate.
PDF
