Environmental Solid-State Cultivation Processes and Bioreactors

Abstract

Solid-state cultivation involves the growth of microorganisms in beds of moist solid particles that have a minimum of free water between the particles. The chapter describes environmentally-related solid-state cultivation processes. For example, some processes use substrates that are residues of agriculture, forestry, or food-processing, thereby reducing the environmental impact of the residue. Other processes do not use residues, but produce products that have environmental applications. Still other processes use environmental-friendly biotransformations that have the potential to replace current industrial processes. Finally, some solid-state cultivation processes can be used to remove pollutants from soil or waste streams. Typically, environmental applications of solid-state cultivation involve large-scale processing of organic solids. The current chapter addresses the design and operation of bioreactors for these processes. It shows how the various bioreactor types can be classified according to the aeration strategy, namely whether the bed of solids is forcefully aerated or not, and according to the agitation strategy, namely the frequency of mixing of the bed of solids. It discusses the current state-of-the-art in optimizing the design and operation of the various bioreactor types, showing how mathematical models that combine microbial growth kinetics and heat and mass transfer phenomena are the most powerful tools that we have available for this task. The chapter concludes by highlighting the necessity to convert current mathematical models into user-friendly computer programs that can guide design and operation decisions for large-scale solid-state cultivation bioreactors.