pH
Fig. 3. Effect of initial pH on citric acid and biomass production by A. niger using banana peel as a substrate under Koji fermentation (values with the same alphabet are not significantly different at the 0.05 level).
A. Karthikeyan, N. Sivakumar / Bioresource Technology 101 (2010) 5552–5556 5555
ranges of optimum pH have been reported for A. niger such as pH 4 in fermentation with beet molasses and corn steep liquor (Walid et al., 2007) and pH 2.6 in solid-state fermentation using cassava bagasse (Prado et al., 2005). Linear regression showed very low correlation between citric acid production and biomass at different pH levels (Fig. 3a).