(2009) argued that microbial oxidation, reduction or degradation of phenolic compounds by fermenting microbes contributes to the decreased phenolic acid content in fermented samples.
Generally, each organic acid has its own production pathway, but some organic acids share the same pathway (Saber et al., 2010). Fungi, in particular Aspergilli, are widely known for their potential to overproduce a variety of organic acids (Karaffa et al., 2001). With respect to the tested fungi, A. oryzae was found to be more effective than R. oryzae and the mixed culture in the total organic acid produced on rice bran. Aspergillus sp. are known to produce citric acid in high productivity and high yield by the fermentation of simple sugar (Tsao et al., 1999), thus explaining the high content of citric acid in single A. oryzae- and mix-cultured-fermented rice bran.