2015): Characterization, structure, and function of extracellular polymeric substances (EPS) of microbial biofilm in biological wastewater treatment systems: a review, Desalination and Water TreatmentTo link to this article: http://dx.
A B S T R A C TA review concerning the definition, extraction, characterization, production, and functions of extracellular polymeric substances (EPS) of microbial aggregates in biological wastewater treatment reactors is given in this paper. EPS are a complex high-molecular-weight mixture of polymers excreted by microorganisms, produced from cell lysis and adsorbed organic matter from wastewater. The EPS fill and form the space between the biofilm constituents, e.g. prokaryotic and eukaryotic microorganisms which inhabit the aggregates. It seems that the EPS matrix may serve as a multipurpose functional element of microbial communities, including adhesion, structure, protection, recognition, and physiology. Due to the metabolic activity of the cells, gradients develop and create different habitats within small distances, allowing a wide variety of organisms to settle and grow in the aggregate. As many of these organisms produce their specific EPS, it is not surprising that an extremely wide variety of microbial aggregates result. All of them have in common their highly hydrated extracellular matrix which is the place the organisms shape their very own microhabitat in which they live. However, as EPS are very complex, the knowledge regarding EPS is far from complete and much work is still required to fully understand their precise roles in the biological treatment process.
Eighteen Erlenmeyer flask containing six different support media [pozzolan, polyvinyl chloride1 (PVC1), polyvinyl chloride2 (PVC2), foam, polyethylene terephthalate (PET) and polystyrene (PS)] were subject to identical volumetric organic loadings and hydraulic retention time in treating synthetic protein ± carbohydrate waste. The objective was to examine the influence of support media on performance of anaerobic denitrification and retention and their resulting impact on system performance and failure. According to the results relative to every control support media, it was noticed that the best support media were the ones in PVC1 and PVC2, with successive reduction rates of 68.33 and 61.93% for chemical oxygen demand (COD), and 55 and 49% for nitrate. On the other hand, in two submerged anaerobic biofilter reactor packed with the support media of PVC1 and PVC2, the reactor with PVC1 media exhibited 89.93% COD and 78.75% nitrate removal efficiency attributable to its higher production of EPSp and EPSc.
Les déchets d'abattoir (sang et contenu du rumen) ont été fermentés par une culture pure de Lactobacillus plantarum. Le produit, avant et après fermentation, a subi des analyses chimiques et microbiologiques. Cette fermentation a permis de baisser le pH à 4,0 du produit final obtenu (biostabilisat). Le taux de protéines a été conservé dans le biostabilisat 22,9 % MS contre 24,6 % MS dans les déchets non traités. Les populations microbiennes indésirables ont subi une grande réduction par les processus de fermentation : les entérobactéries, les entérocoques, les staphylocoques et les clostridia se trouvent chacun à des niveaux inférieurs à 10 ufc/g. Le biostabilisat est utilisé ensuite pour substituer les sources de protéines dans la formule alimentaire de trois lots de 5 rats chacun. Trois formules sont préparées à partir du biostabilisat et du maïs (V/V) 0 % (témoin), 25 % et 50 %. Nous avons suivi les prises alimentaires et les taux de croissance des animaux pendant quatre semaines. Les résultats obtenues indiquent que l'incorporation des déchets d'abattoir jusqu'à un taux de 50 % a permis d'obtenir des performances de croissance comparables à la formule conventionnelle.
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