Production of citric acid from ram horn hydrolysate by Aspergillus niger

Abstract

Ram horn hydrolysate (RHH) was used as a substrate for the microbial production of citric acid using Aspergillus niger NRRL 330 in a submerged culture. Ram horns were hydrolyzed by treating with acid (6N–H 2SO 4) and neutralizing the solution. The amounts of protein, nitrogen, ash, some minerals, total sugars, total lipids and amino acids of the RHH were determined. The effect of different concentrations (1–10% v/v) of RHH on the production of biomass was investigated and a concentration of 8% RHH was found to be optimal. The content of citric acid in the culture broth containing 8% RHH (78 g/l) for 6 d was 26% higher than that of the control culture broth (62 g/l). From this result, RHH was demonstrated to be a suitable substrate for citric acid production. RHH may be a valuable supplement in biotechnology.