Advantages and Progress Innovations of Solid-State Fermentation to Produce Industrial Enzymes

Industrial enzymes are biocatalysts that are commercially used in a variety of commercial sectors such as pharmaceuticals, chemical production, biofuels, food and beverages, and consumer products. Due to advancements in recent years, biocatalysts are considered more economical than use of whole cells and can be used as a unit operation within a process to generate the desired product of interest. Industrial biological catalysis through enzymes has experienced rapid growth in recent years due to their ability to operate at mild conditions, high specificity, and high productivity. Industrial enzymes can be produced by both submerged fermentation (SmF) and solid-state fermentation (SSF). In contrast to the first process, the second bioprocess (SSF) is the cultivation of microorganisms under controlled conditions in the absence of free water. Examples of bioproducts of SSF include industrial enzymes, fuels, and nutrient-enriched animal feeds. Most industrial enzymes are manufactured using the traditional bioprocess of SmF, where microbial cells are suspended in a large volume of water that is stirred and aerated using mechanical devices; such culture conditions dictate the overall physiological behavior of microorganisms provoking biochemical and structural changes affecting the quantity and activity of biocatalysts produced. Among the main advantages of SSF over SmF is a higher volumetric productivity, secretion facilities to get extracellular bioproducts with higher stability, being usually simpler with lower energy requirements, resembling of the natural habitat of some microorganisms, and easier downstream processing. In this chapter we summarize, compare, analyze, and discuss the technological, biochemical, and microbiological advantages of SSF to produce industrial enzymes. Furthermore, culture conditions, aggregation and diffusional phenomena, bioreactors, genetic expression, and protein regulation are covered.