Influence and optimization of growth substrates on indigo formation by a novel isolate Acinetobacter sp. PP-2

In this study, a novel indigo-producing bacterial strain PP-2 was isolated from activated sludge. It was identified as Acinetobacter sp. according to phylogenetic similarity of 16S rRNA gene sequence. This isolate was able to produce indigo from indole by utilizing a wide range of aromatic hydrocarbons. The results of SDS–PAGE analysis showed that the enzyme system induced by phenol was more abundant than that induced by other aromatic hydrocarbons. And the effects of metal ions on indigo production were also investigated, which indicated that the activity of cells induced with phenol could be inhibited by 0.5 mM Fe3+. Response surface methodology (RSM) was applied to optimize the process of indigo bio-production. The results exhibited that the maximal yield was achieved with 157.92 mg L−1 phenol and 205.32 mg L−1 indole. Under the optimal conditions, the indigo yield and transformation efficiency of indole were 202.92 mg L−1 and 88%, respectively.