Hyaluronic acid production by Streptococcus zooepidemicus in marine by-products media from mussel processing wastewaters and tuna peptone viscera

<p>Abstract</p> <p>Background</p> <p>Hyaluronic acid is one of the biopolymers most commonly used by the pharmaceutical industry. Thus, there is an increasing number of recent works that deal with the production of microbial hyaluronic acid. Different properties and characteristics of the fermentation process have been extensively optimised; however, new carbon and protein sources obtained from by-products or cheap substrates have not yet been studied.</p> <p>Results</p> <p>Mussel processing wastewater (MPW) was used as a sugar source and tuna peptone (TP) from viscera residue as a protein substrate for the production of hyaluronic acid (HA), biomass and lactic acid (LA) by <it>Streptococcus zooepidemicus </it>in batch fermentation. Commercial medium formulated with glucose and tryptone was used as the control. The parametric estimations obtained from logistic equations and maintenance energy model utilized for modelling experimental data were compared in commercial and low-cost media. Complete residual media achieved high production (3.67, 2.46 and 30.83 g l^-1of biomass, HA and LA respectively) and a high molecular weight of HA (approximately 2500 kDa). A simple economic analysis highlighted the potential viability of this marine media for reducing the production costs by more than 50%.</p> <p>Conclusions</p> <p>The experimental data and mathematical descriptions reported in this article demonstrate the potential of media formulated with MPW and TP to be used as substrates for HA production by <it>S. zooepidemicus</it>. Furthermore, the proposed equations accurately simulated the experimental profiles and generated a set of interesting parameters that can be used to compare the different bacterial cultures. To the best of our knowledge, this is the first work in which a culture media formed by marine by-products has been successfully used for microbial HA production.</p

Interactive effects of salinity and temperature on planozygote and cyst formation of Alexandrium minutum (Dinophyceae) in culture

The factors regulating dinoflagellate life-cycle transitions are poorly understood. However, their identification is essential to unravel the causes promoting the outbreaks of harmful algal blooms (HABs) because these blooms are often associated with the formation and germination of sexual cysts. Nevertheless, there is a lack of knowledge on the factors regulating planozygote-cyst transitions in dinoflagellates due to the difficulties of differentiating planozygotes from vegetative stages. In the present study, two different approaches were used to clarify the relevance of environmental factors on planozygote and cyst formation of the toxic dinoflagellate Alexandrium minutum Halim. First, the effects of changes in initial phosphate (P) and nitrate (N) concentrations in the medium on the percentage of planozygotes formed were examined using flow cytometry. Second, two factorial designs were used to determine how salinity (S), temperature (T), and the density of the initial cell inoculum (I) affect planozygote and resting-cyst formation. These experiments led to the following conclusions: 1. Low P/N ratios seem to induce gamete expression because the percentage of planozygotes recorded in the absence of added phosphate (-P) was significantly higher than that obtained in the absence of added nitrogen (-N), or when the concentrations of both nitrogen and phosphate were 20 times lower (N/20 + P/20). 2. Salinity (S) and temperature (T) strongly affected both planozygote and cyst formation, as sexuality in the population increased significantly as salinity decreased and temperatures increased. S, T combinations that resulted in no significant cyst formation were, however, favorable for vegetative growth, ruling out the possibility of negative effects on cell physiology. 3. The initial cell density is thought to be important for sexual cyst formation by determining the chances of gamete contact. However, the inoculum concentrations tested did not explain either planozygote formation or the appearance of resting cysts.Peer reviewe

Biphasic toxicodynamic features of some antimicrobial agents on microbial growth: a dynamic mathematical model and its implications on hormesis

<p>Abstract</p> <p>Background</p> <p>In the present work, we describe a group of anomalous dose-response (DR) profiles and develop a dynamic model that is able to explain them. Responses were obtained from conventional assays of three antimicrobial agents (nisin, pediocin and phenol) against two microorganisms (<it>Carnobacterium piscicola </it>and <it>Leuconostoc mesenteroides</it>).</p> <p>Results</p> <p>Some of these anomalous profiles show biphasic trends which are usually attributed to hormetic responses. But they can also be explained as the result of the time-course of the response from a microbial population with a bimodal distribution of sensitivity to an effector, and there is evidence suggesting this last origin. In light of interest in the hormetic phenomenology and the possibility of confusing it with other phenomena, especially in the bioassay of complex materials we try to define some criteria which allow us to distinguish between <it>sensu stricto </it>hormesis and biphasic responses due to other causes. Finally, we discuss some problems concerning the metric of the dose in connection with the exposure time, and we make a cautionary suggestion about the use of bacteriocins as antimicrobial agents.</p> <p>Conclusions</p> <p>The mathematical model proposed, which combines the basis of DR theory with microbial growth kinetics, can generate and explain all types of anomalous experimental profiles. These profiles could also be described in a simpler way by means of bisigmoidal equations. Such equations could be successfully used in a microbiology and toxicology context to discriminate between hormesis and other biphasic phenomena.</p

Revista de Vertebrados de la Estación Biológica de Doñana

Descripción de una nueva subespecie de lagarto ágil (Lacerta agilis garzoni) de los PirineosDiet of the Montagu's Harrier (Circus pygargus) in southwestern Spain SpainObservaciones ornitológicas en la Guayana francesaDaily feeding rhythm of ducks on the marismas of the Guadalquivir and their responses to birds of preyA note on the emetic technique for obtaining food samples from passerine birds.Distribución de contaminantes organoclorados en tejidos de garza imperial (Ardea purpurea) y pato cuchara (Anas clypeata) de la Reserva Biológica de Doñana.Etograma cuantificado del gamo (Dama dama) en libertad.Peer reviewe

A new and general model to describe, characterize, quantify and classify the interactive effects of temperature and pH on the activity of enzymes

16 pages, 5 figures, 3 tablesWe suggest a new and general model to describe the effects of temperature (T) and pH on the catalytic activity of enzymes. Despite the abundance of models to describe those effects, the current proposals are unsatisfactory, except for specific experimental cases in which the interactive mechanism between the two variables does not exist. For both variables, our solution analyses the activated and deactivated phases of an enzyme as phenomena of different nature. The system is described with independent probability functions. The interactive effects between T and pH are introduced with simple auxiliary functions. These functions describe the variations induced by each variable in the parameters that define the effects of the other. The structure of the resulting equation is, in theory and practice, very regular, which facilitates its use, and it is highly descriptive in different scenarios with or without interactive effects. The model was tested on three different enzymatic systems which are specifically designed to produce data for the evaluation of the effect of T and pH on the enzyme activity (A). Afterwards, our model was validated using results from other authors. Briefly, the authors found that: (1) other available models that were compared with our proposal were inefficient and in all cases our model provided the only statistically consistent solution; (2) in four cases, the enzymatic activity could only be explained if interactive effects are accepted; (3) synergy and antagonism concepts for the interaction between T and pH were described and classified; and (4) our solution is universal and independent of the structure of an enzyme and the reaction concerned.The authors wish to thank Ministerio de Ciencia e Innovación (project CTM2010-18411, FEDER funds from the European Union) for financial support. Miguel Angel Prieto Lage was awarded a grant from the JAE predoctoral program financed by the CSIC.Peer reviewe

The influence of substrate structure on the kinetics of the hydrolysis of starch by glucoamylase

8 páginasIn this research the influence of substrate structure on the kinetics of the enzymatic hydrolysis of starch by glucoamylase was evaluated. For this purpose, two substrates of different form and molecular weight were used. In one case, the kinetics of the hydrolysis corresponds to a typical Michaelis-Menten behavior; in the other, a decrease of the hydrolysis rate occurred once a determined substrate concentration was surpassed. The structural differences between the starches, which caused important differences on the rheological properties of their solutions, justify the observed differences in their behavior. Branching of the substrate exerts two opposite effects on the hydrolysis rate because it allows the increase of the number of available points for the enzymatic attack, although the branching increases the steric hindrances and, consequently, the mass transfer resistances. The balance between these two effects is clearly dependent on the substrate concentration.Peer reviewe

Mass transfer control of enzymatic hydrolysis of polysaccharides by glucoamylase

6 pages, 6 figures, 2 tablesA kinetic study of the enzymatic hydrolysis of starch, amylopectin, and glycogen solutions at several concentrations by a commercial glucoamylase was carried out. The results show a decreasing reaction rate zone when starch and amylopectin are used as substrates, at concentrations higher than 50 and 10 g l−1, respectively. In spite of that, the experimental data can be well fitted to a substrate inhibition model. Additional experiments [(i) working at lower substrate concentrations but keeping the same substrate/enzyme ratio; (ii) in static or shaken conditions; (iii) with/without addition of a thickener agent] led us to conclude that hydrolysis of high viscosity starch and amylopectin solutions is controlled by the mass transfer rate.We acknowledge CAICYT and CICYT for their economic support (Projects 1D87060 and BIO89-0264)Peer reviewe