Development Of Microbial Activity Research Articles

Freshwater bivalves and their environmental conditions in a Jurassic lacustrine system (Cañadón Asfalto Formation) from Patagonia, Argentina

At the moment, two freshwater bivalve species were described for the continental Jurassic of Patagonia: Diplodon simplex Morton and Diplodon matildensis Morton from La Matilde Formation of the Santa Cruz province. The Cañadón Asfalto Formation located in Chubut province exhibits a high diverse invertebrate fossil fauna preserved mainly in lacustrine facies, which includes clam shrimps, bivalves, gastropods, ostracods and insects. However, few studies have been carried out on freshwater bivalve of this geological unit. In this work, a morphological description of bivalve assemblage and paleoenvironment analysis from the Cañadón Asfalto Formation was performed. Forty samples were collected from three stratigraphic levels at the Cañadón Asfalto locality. These levels are ash fall tuffs rich in glass particles accumulated in a lacustrine system with development of microbial activity. Morphological analyzes of outline and sizes were performed at each level. Our results showing the smallest-sized association of unionids recorded for the Jurassic time with size ranging from 7.6-11.7 mm long and 5.2-7.6 mm high. The environmental influence of pyroclastic falls could have played an important role in the development of the sizes of populations and shells.

Antioxidant and Antimicrobial Effect of Biodegradable Films Containing Pitaya (Stenocereus thurberi) Extracts during the Refrigerated Storage of Fish.

This study focused on the quality loss inhibition of fish muscle during refrigerated storage. Two parallel experiments were carried out that were focused on the employment of pitaya (Stenocereus thurberi) extracts in biodegradable packing films. On the one hand, a pitaya-gelatin film was employed for hake (Merluccius merluccius) muscle storage. On the other hand, a pitaya-polylactic acid (PLA) film was used for Atlantic mackerel (Scomber scombrus) muscle storage. In both experiments, fish-packing systems were stored at 4 °C for 8 days. Quality loss was determined by lipid damage and microbial activity development. The presence of the pitaya extract led to an inhibitory effect (p < 0.05) on peroxide, fluorescent compound, and free fatty acid (FFA) values in the gelatin-hake system and to a lower (p < 0.05) formation of thiobarbituric acid reactive substances, fluorescent compounds, and FFAs in the PLA-mackerel system. Additionally, the inclusion of pitaya extracts in the packing films slowed down (p < 0.05) the growth of aerobes, anaerobes, psychrotrophs, and proteolytic bacteria in the case of the pitaya-gelatin films and of aerobes, anaerobes, and proteolytic bacteria in the case of pitaya-PLA films. The current preservative effects are explained on the basis of the preservative compound presence (betalains and phenolic compounds) in the pitaya extracts.

Employment of Flake Ice Systems Including Natural Preservative Compounds for the Quality Enhancement of Chilled Seafood-A Review.

Marine species deteriorate rapidly post-mortem as a consequence of a variety of biochemical and microbial breakdown mechanisms. Due to the increasing demand for high-quality fresh seafood, different strategies are now available to retard spoilage for as long as possible. The present study provides an overview of a recently proposed strategy based on the addition of natural compounds to marine species. In this strategy, different kinds of natural preservative compounds are included in the flake-ice medium that is commonly used for chilled storage. Natural sources tested for this purpose include low-molecular-weight organic acids and different kinds of extracts of plants, macroalgae, and by-products resulting from marine species commercialization. The preservative action of such treatments is analyzed according to the effect on different deteriorative mechanisms (i.e., lipid hydrolysis, oxidation, and microbial activity development), as well as on the resulting sensory acceptability and shelf-life time. The basic objective of this review is to provide an overview concerning the positive effect that the presence in an icing system of natural preserving compounds may have on the quality of chilled marine species. Furthermore, various potential avenues are proposed to develop the practical and commercial employment of this technological strategy.

Autotrophic denitrification supported by biotite dissolution in crystalline aquifers (1): New insights from short-term batch experiments

We investigate denitrification mechanisms through batch experiments using crushed rock and groundwater from a granitic aquifer subject to long term pumping (Ploemeur, France). Except for sterilized experiments, extensive denitrification reaction induces NO3 decreases ranging from 0.3 to 0.6mmol/L. Carbon concentrations, either organic or inorganic, remain relatively stable and do not document potential heterotrophic denitrification. Batch experiments show a clear effect of mineral dissolution which is documented through cation (K, Na, Ca) and Fluoride production. These productions are tightly related to denitrification progress during the experiment. Conversely, limited amounts of SO4, systematically lower than autotrophic denitrification coupled to sulfur oxidation stoichiometry, are produced during the experiments which indicates that sulfur oxidation is not likely even when pyrite is added to the experiments.Analysis of cation ratios, both in isolated minerals of the granite and within water of the batch, allow the mineral dissolution during the experiments to be quantified. Using cation ratios, we show that batch experiments are characterized mainly by biotite dissolution. As biotite contains 21 to 30% of Fe and 0.3 to 1.7% of F, it constitutes a potential source for these two elements. Denitrification could be attributed to the oxidation of Fe(II) contained in biotite. We computed the amount of K and F produced through biotite dissolution when entirely attributing denitrification to biotite dissolution. Computed amounts show that this process may account for the observed K and F produced.We interpret these results as the development of microbial activity which induces mineral dissolution in order to uptake Fe(II) which is used for denitrification. Although pyrite is probably available, SO4 and cation measurements favor a large biotite dissolution reaction which could account for all the observed Fe production. Chemical composition of groundwater produced from the Ploemeur site indicates similar denitrification processes although original composition shows mainly plagioclase dissolution.

Comparative studies of aerobic and anaerobic treatment of MSW organic fraction in landfill bioreactors

Four simulated landfill bioreactors operating under different experimental conditions were evaluated in this study. The reactors were filled with the organic fraction of municipal solid wastes (MSW) and operated as: anaerobic, anaerobic with pH adjustment, semi‐aerobic and intermittent aeration bioreactors. The parameters studied in the leachate included pH, redox potential, BOD5, COD, DOC, SO4 2−, NH4 +‐N, NO3 −‐N, NO2 −‐N, Cl− and electrical conductivity. Also, the MSW mass settlement was measured at certain intervals. Leachate recirculation took place in all bioreactors. The results indicated that the intermittent aerobic reactor had higher organic and ammonia removal efficiencies than the anaerobic versions. Furthermore, the necessary stabilization time was reduced under aerobic conditions and the leachate toxicity decreased more rapidly. The pH adjustment in the anaerobic bioreactor had positive results in the decomposition of the organic matter enhancing the development of microbial activity.

Regulating the hydrolysis of organic wastes by micro-aeration and effluent recirculation

In this study, the effects of micro-aeration and liquid recirculation on the hydrolysis of vegetable and flower wastes during two-phase solid-liquid anaerobic digestion were assessed. To accomplish this, we evaluated the hydrolysis of five batches of waste that were treated under the following conditions: anaerobic, insufficient micro-aeration (aeration for 5 min every 24 h), and sufficient micro-aeration (aeration for 5 min every 12, 4 and 1h). Hydrolysis was found to depend on the level of micro-aeration. Specifically, insufficient micro-aeration led to unstable and decreased performance. Conversely, sufficient micro-aeration promoted the hydrolysis of easily biodegradable carbohydrates and proteins, but the microbial activity was later impaired by liquid recirculation using methanogenic effluent. The hydrolysis efficiency under anaerobic conditions was comparable to the efficiency observed under sufficient micro-aeration, while the cumulative TOC of the anaerobic batch was 1.4-2.4 times higher than that of the micro-aerated batches. In addition, liquid recirculation did not have a negative effect on the development of microbial activity under anaerobic conditions, which resulted in the lignocelluloses having a higher hydrolysis efficiency.

Changes in the fermentation end-product profile in the GIT of piglets during post-colostrum suckling period

Pre-weaning development of microbial activity has an effect on post-weaning establishment of the gastro-intestinal tract (GIT) microbiota. An in vivo study was conducted, to evaluate the effect of age on fermentation end-product profiles during the post-colostrum suckling period, as the variation in composition of mature milk is minimum. Sixteen piglets from two litters (eight per litter) were selected. During the study, piglets had free access to sow's milk, but no creep feed, nor antibiotic treatments. Two piglets from each litter were sacrificed on d 11, 18, 25 and 32 of age. The digesta samples were collected from the beginning and end of the small intestine, caecum and colon. Samples were analyzed for fermentation end-product concentrations. Combining the results from all the GIT sites, it was observed that, total VFA concentration increased with age of the piglets. There was a significant rise in acetic acid concentrations, with a significant decrease in lactic acid concentrations from d11 to d32, while the proportions of SCFA, (acetic acid not, vert, similar 72%, propionic acid not, vert, similar 15% and butyric acid not, vert, similar 6% of total VFA) and ammonia concentrations remained unchanged. These results clearly suggest that, the microbial activity in terms of fermentation end-product profile skewed from lactic acid to acetic acid as a major product during the post-colostrum suckling period. This may be attributed to lower substrate availability due to increased number of microbes or increased diversity in the microbiota in time.

Comparaison de L'Activite Biologique de Differents Charbons Actifs en Grains Comparison of Biological Activity of Different Types of Granular Activated Carbons

In drinking water production plants, two phenomena occur into the granular activated beds: physical adsorption of organic matter, especially of micropollutants and biodegradation of a part of the dissolved organic carbon. In order to get a better understanding of the development of biological activity a comparative test has been studied on four GAC from different origins and way of manufacturing, and with various characteristics (porosity, density, specific surface,…). For that purpose, preliminary experiments led to the choice of an organic compound, nitro-4-phenol, which presents an average biodegradability. Four minicolumns, each one filled with one GAC, plus another one filled with sand (as a non-porous reference material) were run in parallel at a flow rate of 0.5 l h−1 (i.e. a linear velocity of about 5 m h−1). In the first step of the test, GAC were saturated in batch with an aqueous solution of nitro-4-phenol at a standard temperature of 25°C. In the second step, columns of GAC were fed with a solution of nitro-4-phenol at a concentration of 13.9 mg l−1 enriched with nutrients buffered at pH 7.9; this led to the development of microbial activity. The biodegradation occured rapidly, three days after the columns have been fed. When equilibrium was reached after a running of 10–15 days, the biodegradation yield stabilized at about 50% for all kinds of GAC, with no significant differences. Oxygen appears to be a determinant factor for a total mineralization of the nitro-4-phenol. Dissolved oxygen and temperature were shown to control the rate of bioactivity. At lower concentrations of nitro-4-phenol, the oxygen demand decreased and thus allowed a larger biodegradability which could reach 100% in yield. This yield fell down to about 50% when the temperature was maintained at 5°C. These observations were quite similar for all types of GAC tested (pinewood based chemically or physically activated - bituminous coal based or coconut based) and for sand. All these experiments have been realized at a concentration in ammoniacal nitrogen of 6.5 mg l−1. A lack in this component did not lead to a reduction of the biodegradation. So far, it seems that physical characteristics of GAC (porosity, raw material,…) do not play an important role in the development of biological activity, suggesting that microorganisms are mainly fixed on the external surface of GAC.

Transformations of structural phenylpropanoids during cell wall digestion

Phenylpropanoids limit the degradation of cell walls of roughages in herbivores but at the same time undergo transformations in the digestive tract. This review outlines the main transformations that occur in the rumen. All the monomeric aromatics tested are fully degraded under anaerobic conditions which favour electron transfer. Six main strains of bacteria degrade monomeric phenols in the rumen by several mechanisms. In addition, some fungi and bacteria are able to release, and possibly to metabolise the esterified hydroxycinnamic acids found in forage cell walls. The first step in the degradation of these acids is their reduction to non-toxic compounds, which are often growth factors. However, total degradation of monoaromatics is difficult to achieve in vivo because of the small population of organisms able to metabolise them abd the limited transit time of the substrates in the rumen. Oligolignols are also degraded to different extents depending on their size and molecular structure. Lignins are partly solubilised during cell wall degradation. They may also undergo other transformations such as demethylation and dehydroxylation. The amount of lignin that seems to be degraded in rumen fluid is low but probably higher than under other anaerobic environments over the same period of time. It is generally accepted that the digestibility of forage lignins is low. However, the wide range of values measured (from minus 0.46 to 0.64) is related either to the measurement method or to the transformations that the lignins may undergo in the digestive tract, or to both. An indigestible fraction of lignins could serve as a reliable cell wall marker but none of the fractions used to date has proved entirely satisfactory for this purpose. Future research in this field would involve better knowledge about the transformation of phenylpropanoids and the development of microbial activity on these compounds. This would improve phenolics degradation and consequently carbohydrate utilization.

Development of microbial activity in the alimentary tract of lambs.

Development of microbial activity in the alimentary tract of lambs.