ABSTRACT
354Solid-state fermentation (SSF) is a low cost and highly productive bioprocess for production of a wide range of bioproducts; however, several factors may limit its use at pilot and industrial level. Moreover, it is of a great importance the bioreactor geometry according to the microorganisms characteristics used for the fermentation. Filamentous fungi are used for several applications and their requirements in oxygen and unmixed beds make it suitable for production of high value metabolites in SSF bioreactors. Packed bed bioreactors are one of the most used bioreactors in SSF at Lab-scale because of it is possible to study variables of the process as temperature, airflow, particle size of the substrate, and humidity; but it is required a constant and very close monitoring to avoid negative inherent effects as temperature increment and humidity loss. For these reasons, there is relevant to evaluate other characteristics of the bioreactors in order to propose improvements to maintain the study variables during the fermentation process. Then, it is important to add heat exchangers with the bioreactor as solids behavior (degradation and compaction) in order to enhance the heat dissipation from the solids, and other techniques to maintain humidity during the fermentation as in drum bioreactors (adding water by spraying over the bed with agitation of the medium). Because of air force results insufficient to remove heat from the matrix, a combination of convection and conduction for cooling system result in a better way to maintain temperature over the fermentation time. In the present work, operational and engineering aspects of bioreactors are showed and their effect over SSF as humidity, temperature, and solid support. Also, it is mentioned the relationship of these aspects over SSF and the variables of the process.
