Chemical and bacteriological composition of granular methanogenic sludge

Abstract

Methanogenic sludge granules grown on waste water from a sugar refinery consisted of several bacterial morphotypes embedded in a matrix of extracellular material. Comparison of critical point drying and freeze-drying methods for preparing samples for scanning electron microscopy to determine the presence of extracellular material indicated that the former method permitted observations of extracellular material and intact cells. The effects of different extraction methods used for isolation of these extracellular polymers was also investigated by scanning electron microscopy. Of the various extraction procedures (EDTA, NaOH, autoclaving, water–phenol), water–phenol left most of the cells intact and was found to be a very efficient method of extraction. Extracellular polymers equivalent to 10–20 mg hexose/g of granules were extracted. The high resistance of the granules against disintegration by various chemical methods suggested that different extracellular polymers and probably different groups of organisms contributed to the matrix in which the bacteria were embedded. The chemical composition of the granules did not differ from the composition of bacteria in general. The buoyant density of 1.00–1.05 g∙g−1of the granules indicated that a simple agglomeration was the mechanism by which these methanogenic consortia improved their settling characteristics.

Enhancement of granulation and start‐up in the anaerobic sequencing batch reactor

“…Table 7 shows the results of several tests designed to determine the number of specific bacterial groups in granules [31,33].…”

“…Traditionally, scanning electron microscopy (SEM) has been used to qualitatively determine the types of bacteria present (rods, cocci, etc.). The bacteria observed with the SEM could then be compared to the morphologies of known methanogens and other anaerobes, and a qualitative analysis could be made with the identification of some of the species present within the granule [10,31,37,64,80,89,102,119]. More recently, immunological probes and fluorescence techniques have become popular methods of identifying specific species of bacteria, especially methanogenic species [34,76,88, 101,118,158].…”

“…More recently, immunological probes and fluorescence techniques have become popular methods of identifying specific species of bacteria, especially methanogenic species [34,76,88, 101,118,158]. The immunological probes utilize polyclonal antibodies specific for a given bacterial species to determine the presence of that Methanothrix has especially been singled out as a common bacterium in most granular sludges [31,37,64,102]. It has been postulated that in anaerobic systems with low acetate concentrations, Methanothrix will out-compete Methanosarcina due to the former's lower Kn, value (higher affinity) for acetate, although the two species are almost always present within the same granule in varying degrees.…”

Tratamiento biológico de aguas residuales: Principios, modelación y diseño

“…El piruvato, lactato y etanol son compuestos que pueden ser fácilmente fermentables por varias BSR (Dolfing, 1987;Widdel et al, 1988). Una característica importante de las BSR es su habilidad para llevar a cabo la oxidación acetogénica junto con las arqueobacterias metanogénicas hidrogenotróficas (AMH), como se describe para los co-cultivos de AMH con Desulfovibrio sp.…”

Effect of ferrous iron on the settling properties of granular sludge in a UASB reactor

“…Many factors contribute, in one form or another, to the granulation process [6,7]. Granulation may be initiated by bacterial adsorption and adhesion to inert matters, to inorganic precipitates [2,8], and/or to each other through physico-chemical interactions and syntrophic associations [9]. These substances serve as initial precursors (carriers or nuclei) for further bacterial growth.…”