Microbial activity biomass

Merrington, G., Rogers, S.L. and VanZwieten, L. (2002). The potential impact of longterm copper fungicide usage on soil microbial biomass and microbial activity in an avocado orchard , Australian Journal of Soil Research, 40, 749-759. 

Fig. 33.4. Factors controlling rates of microbial activity in the simulation depicted in Figure 33.3, for acetotrophic sulfate reduction (top) and acetoclastic methanogenesis (bottom). Factors include the thermodynamic potential factor Ft, kinetic factors FD = wac/C ac + Kq) and FA = mso4/(mso4 + K A), and biomass concentration [A],...

The concept described in Figure 3.1 is simple compared to the complexity of microbial systems. However, it reflects basic aspects of what is important related to the processes in a microbial system a distinction between active biomass and substrate in both soluble and particulate forms. At the same time, the... 

Although the investigations of both Raunkjaer et al. (1995) and Almeida (1999) showed that removal of COD — measured as a dissolved fraction — took place in aerobic sewers, a total COD removal was more difficult to identify. From a process point of view, it is clear that total COD is a parameter with fundamental limitations, because it does not reflect the transformation of dissolved organic fractions of substrates into particulate biomass. The dissolved organic fractions (i.e., VFAs and part of the carbohydrates and proteins) are, from an analytical point of view and under aerobic conditions, considered to be useful indicators of microbial activity and substrate removal in a sewer. The kinetics of the removal or transformations of these components can, however, not clearly be expressed. Removal of dissolved carbohydrates can be empirically described in terms of 1 -order kinetics, but a conceptual formulation of a theory of the microbial activity in a sewer in this way is not possible. The conclusion is that theoretical limitations and methodological problems are major obstacles for characterization of microbial processes in sewers based on bulk parameters like COD, even when these parameters are determined as specific chemical or physical fractions. 

Without appropriate cleanup measures, BTEX often persist in subsurface environments, endangering groundwater resources and public health. Bioremediation, in conjunction with free product recovery, is one of the most cost-effective approaches to clean up BTEX-contaminated sites [326]. However, while all BTEX compounds are biodegradable, there are several factors that can limit the success of BTEX bioremediation, such as pollutant concentration, active biomass concentration, temperature, pH, presence of other substrates or toxicants, availability of nutrients and electron acceptors, mass transfer limitations, and microbial adaptation. These factors have been recognized in various attempts to optimize clean-up operations. Yet, limited attention has been given to the exploitation of favorable substrate interactions to enhance in situ BTEX biodegradation. 

The parameters for characterising soil microbial activity used in the reviewed research results are total microbial biomass, diverse enzymatic parameters, carbon turnover parameters andffiycorrhization, ... 

Flie/Jbach, A. Martens, R. Reber, H.H. Soil microbial biomass and microbial activity in soils treated with heavy metal contaminated sewage sludge. Soil Biol. Biochem. 1994, 26, 1201-1205. 

Active zones of Fe oxide reduction in soils can be easily recognized as bleached areas showing the grey colour of the matrix minerals after removal of the staining Fe oxides. Such zones can only form where a microbially metabolizable biomass is available, for example in the lower top soil or along roots. In poorly aerated soils with large structural units (e.g. prisms), root mats often develop only at the surface of these units and bleach their surfaces, whereas the interior is still coloured... 

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