Secreted Microbial Enzymes for Organic Compound Degradation

Abstract

Microbes in the belowground environment draw nutrition from the complex organic biomass found in the soil. Their primary means of interaction with the molecular components of their environment is via extracellular enzymes that deconstruct high molecular weight organic compounds in the soil. These include the natural carbohydrates and polyaromatic compounds of decaying plant and microbial biomass, predominantly cellulose, lignin, and chitin. Also important are several classes of organic xenobiotics of anthropogenic origin, such as polyaromatic hydrocarbons, polychlorinated biphenyls, and diverse synthetic fertilisers and pesticides. Many biotechnological processes have now been established that exploit this natural toolbox of biomass-degrading enzymes for the industrial production of biofuels or biomaterials. However, our understanding of the natural role these enzyme systems play within the soil remains limited. It is well accepted, for example, that an active microbiota is vital for productive agriculture, but the impacts of soil management regimes on the microbiota remain opaque. In this chapter, we review current knowledge on microbial enzyme secretion and activity in the soil and explore current research into the regulation of enzyme production. We summarise the range of enzyme activities found in the soil environment and their contribution to the recycling and degradation of organic compounds, a vital elemental turnover that may be impacted by a warming climate. The methods employed by microbes to maintain an effective level of enzyme activity in the extracellular environment are described. Finally, we discuss the ways in which we might make use of microbial enzymes to improve the sustainability of agriculture and industry.