Production of Single Cell Protein in Stickwater by Lactobacillus acidophilus and Aspergillus niger

The aim of this study was to investigate production of single cell protein (SCP) using Lactobacillus acidophilus and Aspergillus niger in stickwater from fish meal factories. Stickwater was used as substrate for L. acidophilus and A. niger and compared with standard medium as control. The maximum chemical oxygen demand reduction by L. acidophilus was achieved at 55.4 and 86.4% and that by A. niger at 74.1 and 97.7% in the control treatment and stickwater, respectively. The maximum protein obtained by L. acidophilus was at 71.13 and 68.37% and that by A. niger at 51.36 and 48.66% for the control and stickwater, respectively. The amount of RNA by L. acidophilus was also found to be at 15.27 and 15.04% and that by A. niger at 9.36 and 9.09% for the control and stickwater, respectively. By substitution of stickwater and control treatment, in both cultures, maximum and minimum amounts of glutamic acid and methionine were obtained. According to the results of this study, the substitution of stickwater (as carbon source) was adequate for the production of SCP. The chemical score of the SCP in the biomass of both L. acidophilus and A. niger in stickwater indicates that the amino acid profile of SCP fulfils adult human nutritional requirements, except for methionine. In addition, the chemical score of the SCP shows that lysine, methionine, and phenylalanine are the most limiting amino acids and that other amino acids are present at levels exceeding the requirements of juvenile common carp.