Evolutionary adaptation of Aspergillus niger for increased ferulic acid tolerance

Abstract

Aims: To create an Aspergillus niger mutant with increased tolerance against ferulic acid using evolutionary adaptation.

Methods and results: Evolutionary adaptation of A. niger N402 was performed by consecutive growth on increasing concentrations of ferulic acid in the presence of 25 mmol l^-1 d-fructose, starting from 0·5 mmol l^-1 and ending with 5 mmol l^-1 ferulic acid. The A. niger mutant obtained after six months, named Fa6, showed increased ferulic acid tolerance compared to the parent. In addition, Fa6 has increased ferulic acid consumption and a higher conversion rate, suggesting that the mutation affects aromatic metabolism of this species. Transcriptome analysis of the evolutionary mutant on ferulic acid revealed a distinct gene expression profile compared to the wild type. Further analysis of this mutant and the parent strain provided the first experimental confirmation that A. niger converts coniferyl alcohol to ferulic acid.

Conclusions: The evolutionary adaptive A. niger mutant Fa6 has beneficial mutations that increase the tolerance, conversion rate and uptake of ferulic acid.

Significance and impact of the study: This study demonstrates that evolutionary adaptation is a powerful tool to modify micro-organisms towards increased tolerance to harsh conditions, which is beneficial for various industrial applications.

Keywords: Aspergillus; adaptive evolution; aromatic metabolism; cell factory; ferulic acid tolerance; mutagenesis.