Environmental Solid-State Cultivation Processes and Bioreactors

Abstract

Solid-state cultivation involves the growth of microorganisms in beds ofmoist solid particles that have a minimum of free water between theparticles. The chapter describes environmentally-related solid-statecultivation processes. For example, some processes use substrates thatare residues of agriculture, forestry, or food-processing, therebyreducing the environmental impact of the residue. Other processes do notuse residues, but produce products that have environmental applications.Still other processes use environmental-friendly biotransformations thathave the potential to replace current industrial processes. Finally,some solid-state cultivation processes can be used to remove pollutantsfrom soil or waste streams. Typically, environmental applications ofsolid-state cultivation involve large-scale processing of organicsolids. The current chapter addresses the design and operation ofbioreactors for these processes. It shows how the various bioreactortypes can be classified according to the aeration strategy, namelywhether the bed of solids is forcefully aerated or not, and according tothe agitation strategy, namely the frequency of mixing of the bed ofsolids. It discusses the current state-of-the-art in optimizing thedesign and operation of the various bioreactor types, showing howmathematical models that combine microbial growth kinetics and heat andmass transfer phenomena are the most powerful tools that we haveavailable for this task. The chapter concludes by highlighting thenecessity to convert current mathematical models into user-friendlycomputer programs that can guide design and operation decisions forlarge-scale solid-state cultivation bioreactors.