Isolation of a novel strain Aspergillus niger WH-2 for production of L(+)-tartaric acid under acidic condition

Abstract

Objectives: To isolate a novel cis-epoxysuccinate hydrolase (CESH)-producing fungus for production of L( +)-tartaric acid, before this, all strains were selected from bacteria.

Results: A CESH-producing fungus was first isolated from soil and identified as Aspergillus niger WH-2 based on its morphological properties and ITS sequence. The maximum activity of hyphaball and fermentation supernatants was 1278 ± 64 U/g and 5.6 ± 0.3 U/mL, respectively, in a 5 L fermenter based on the conditions optimized on the flask. Almost 70% of CESH was present in hyphaball, which maintained 40% residual activity at pH 4.0 and showed a good acid stability (pH 3.0-10.0), high conversion rate (> 98%), and enantioselectivity (EE > 99.6%). However, the reported CESHs from bacteria can't be catalyzed under acidic conditions.

Conclusions: The Aspergillus niger WH-2 was the first reported CESH-producing fungus, which could biosynthesize L ( +)-tartaric acid under acidic conditions and provide an alternative catalyst and process.

Keywords: Aspergillus niger; Isolation; L(+)-Tartaric acid; cis-Epoxysuccinate hydrolase.