Generally, smaller substrate particles provide a larger
surface area for microbial attack but if they are too
small may result in substrate agglomeration as well as
poor growth. In contrast, larger particles provide better
aeration but a limited surface for microbial attack.
Therefore, a compromised particle size must be selected
for each particular process (Pandey et al., 1999a).
Research on the selection of suitable substrates for
SSF has mainly been centred around agro-industrial residues
due to their potential advantages for filamentous
fungi, which are capable of penetrating into the hardest
of these solid substrates, aided by the presence of turgor
pressure at the tip of the mycelium (Ramachandran
et al., 2004). In addition, the utilisation of these agroindustrial
wastes, on the one hand, provides alternative
substrates and, on the other, helps in solving pollution
problems, which otherwise may cause their disposal
(Pandey et al., 1999a).
SSF offers numerous advantages over SmF such as
simpler technique and lower cost (Table 2). However,
there are few designs available in the literature for biore-
actors operating in solid-state conditions. This is princi-