ABSTRACT
This chapter discusses a wide variety of chemical transformations occurring in nature follow differing kinetics and in particular. It focuses on the role of microorganisms, which are involved in almost all of the natural chemical transformations. The chapter describes the anabolic part of the microbial metabolism, though no cell anabolism is possible without an energy source, exploited by the catabolic metabolism. It also discusses two hypotheses endogenous respiration in the growth-decay model. The endogenous metabolism is considered as an oxygen-consuming process, while in the death-regeneration case and it does not consume oxygen, representing just the undoing of the cell, though part of the recycled material will be again metabolized, and hence will consume oxygen. To reproduce the reactions, the biochemical oxygen demand (BOD) must be used, consisting of measuring the oxygen uptake of a batch in which substrate and bacteria interact like in their natural environment. The BOD bottle method reproduces the natural conditions and the metabolic capabilities of bacteria.
