*4.3.1 Submerged fermentation*

When fermentation is performed with some free flowing nutrient media; it is termed as SmF [84]. In industry, enzymes are produced mostly by SmF, primarily due to the much simplified processes associated with scale-up compared to those involved for scale-up in SSF [85]. In fact, some other important factors like indulgence in controlling process parameters, monitoring and downstream processing makes SmF more significant [86]. Only a few designs are available in literature for SSF based bioreactors. This is principally due to several problems encountered in case of SSF for controlling various parameters like pH, temperature, aeration and moisture content. Fungal cellulase production is largely dependent on media composition and culture conditions. Thus development of a suitable fermentation strategy is necessary for full exploitation of potential of microorganism used for fermentation [87]. Several reports are available for cellulase production using SmF. Karthikeyan et al. [88] reported cellulase production from *Penicillium* strain K-P in liquid medium supplemented with different carbon and nitrogen sources at varying pH and temperature, maximum cellulase activity was observed on fifth day (pH 3.0 and 30°C) in the presence of fructose and ammonium nitrate as carbon and nitrogen source respectively. Narasimha et al. [89] reported maximum cellulase production using *A. niger* on medium (pH 5) supplemented with 1% CMC or sawdust.
