Valorization of tannin rich triphala waste for simultaneous tannase and gallic acid production under solid state fermentation by Aspergillus niger

Abstract

This research aimed to study gallic acid production by the activity of tannase secreted by Aspergillus niger ATCC 16888 under solid-state fermentation using Triphala waste. Gallic acid is commonly extracted from Triphala using hot water. The residue contains a high number of hydrolyzable tannins. The parameters for the SSF were studied which included a nitrogen supplementary with an aeration supply. Results indicated that Triphala waste (TW) was a good substrate for valorization with tannase and gallic acid production by A. niger. When the fermentation was supplemented with 0.75% sodium nitrate that combination provided the highest biomass, tannase and gallic acid concentrations of 254.2 ± 15.4 mg g⁻¹_DS, 49.4 ± 2.0 U g⁻¹_DS and 13.3 mg g⁻¹_DS, respectively, while the aeration at 0.3 vvm (0.75% sodium nitrate supplementary) provided the highest biomass tannase and gallic productions of 445.0 ± 43.0 mg g⁻¹_DS, 53.3 ± 5.3 U g⁻¹_DS and 168.5 ± 5.0 mg g⁻¹_DS, respectively. The results indicated that the number of nitrogen atoms and the rate of aeration had significant parameters for tannase production. The carbon/nitrogen (C/N) ratio of the substrate correlated with tannase production of A. niger. The optimum C/N ratio of the substrate for tannase production was approximately 20.

Keywords:

• Aspergillus niger
• gallic acid
• solid state fermentation
• tannase
• tannin
• triphala

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Conflict of interest

The authors declare that they have no conflict of interest.

Declaration of competing interest

The authors report no declarations of interest.

Additional information

Funding

The authors would like to thank the National Research Council of Thailand for the financial support which contributed to King Mongkut’s Institute of Technology Ladkrabang [2560NRCT32069]. The authors are also grateful to the Institute of Thai Traditional Medicine, Department for Development of Thai Traditional Medicine and Alternative Medicine, Ministry of Public Health, Thailand for providing facilities to carry out this research.