3.1. Effect of initial moisture content
The maximum level of citric acid production was observed at 70% moisture content. A significant increase (p < 0.05) was observed in citric acid production from 50–70%, but this decreased after that (Fig. 1). Maximum fungal biomass was obtained at the range of 70–80% initial moisture content of solid-state fermentation. It was already reported that at 78% moisture had increased the citric acid production (Shojaosadati and Babeipour, 2002). Moisture content of solid-state fermentation interferes with the physical properties of the solid particle and affects the process. Increased moisture reduces the porosity of the substrate (Kumar et al., 2003) and thereby limiting the oxygen transfer (Pandey et al., 2000). Low substrate moisture results in low product formation due to decrease in diffusion of solutes, nutrients and gas to the