Screening of genes of secreting acetic acid from Aspergillus niger H1 to improve phosphate solubilization

A primary cDNA library of Aspergillus niger H1 was constructed using the switching mechanism at the 5′ end of the RNA transcript (SMART) technique. A total of 169 clones exhibited halos when grown on tricalcium phosphate medium, and the H-46 clone displayed a clear halo. The full-length cDNA of the clone H-46 clone was 1 407 bp in length with a complete open reading frame (ORF) of 816 bp, and it encoded a protein that contained 272 amino acids. Multiple alignment analysis revealed a high degree of homology between the ORFs of the H-46 clone and the Bax inhibitor family (BI-1-like) proteins of other fungi. Acetic acid was secreted by Escherichia coli DH5α that express the BI-1-like gene. The level attained was 492.52 mg L−1, which was associated with the release of 0.212 mg mL−1 of soluble phosphate at 28 h. These results showed that the heterologous expression of BI-1-like genes in Eschericha coli DH5α increased the secretion of acetic acid by altering the membrane permeability and enhancing the solubility of phosphate (P).