Solid-state fermentation (SSF) involves the growth of microorganisms on moist solid particles with a minimum of free water in the inter-particle spaces. Due to the particular environmental conditions imposed on the microorganism, this fermentation technique has the potential to produce selected microbial products better than submerged liquid fermentation. However, SSF processes studied in the laboratory are rarely scaled-up to commercial purposes. One of the major barriers is the difficulty in controlling the water content and temperature of the bed in large-scale bioreactors [1–3].