Valorization of Banana Peel for Citric Acid Production under Solid State Fermentation with Aspergillus niger

Abstract

Valorization of banana peel (BP) through solid state fermentation (SSF) was aimed<br /> in this research. The appropriate conditions of citric acid (CA) production by SSF of<br /> Aspergillus niger were investigated. Firstly, the optimum initial pH of the BP and the<br /> aeration rate were studied by conducting SSF in a 250-mL flask and 2-L glass column,<br /> respectively. It was found that the initial pH of the BP and aeration rates affected the CA<br /> production. The results showed that the initial pH of 5.0 and 1.0 vvm aeration were appropriate for the CA production of A. niger using BP as a substrate. The problem of rising temperature during SSF was found when applying the optimum condition to the SSF<br /> in the 20-L packed bed bioreactor (PBB), which caused a decrease in the CA production<br /> compared to that of the glass column. The cooling air jacket constructed to the PBB to<br /> remove the heat during the SSF helped increase the CA production from that in the PBB.<br /> The maximum CA production in the 20-L air-jacketed PBB was 124.0±19.2 mg g–1DS.