Transformation of Litchi Pericarp-Derived Condensed Tannin with Aspergillus awamori.

Sen Lin,John Shi,Bao Yang,Xuewu Duan,Qing Li,Yueming Jiang,Mingwei Zhang

doi:10.3390/ijms17071067

Abstract

Condensed tannin is a ubiquitous polyphenol in plants that possesses substantial antioxidant capacity. In this study, we have investigated the polyphenol extraction recovery and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity of the extracted polyphenol after litchi pericarp is treated with Aspergillus awamori, Aspergillus sojae or Aspergillus oryzae. We have further explored the activity of A. awamori in the formation of condensed tannin. The treatment of A. awamori appeared to produce the highest antioxidant activity of polyphenol from litchi pericarp. Further studies suggested that the treatment of A. awamori releases the non-extractable condensed tannin from cell walls of litchi pericarp. The total extractable tannin in the litchi pericarp residue after a six-time extraction with 60% ethanol increased from 199.92 ± 14.47–318.38 ± 7.59 μg/g dry weight (DW) after the treatment of A. awamori. The ESI-TOF-MS and HPLC-MS2 analyses further revealed that treatment of A. awamori degraded B-type condensed tannin (condensed flavan-3-ol via C4–C8 linkage), but exhibited a limited capacity to degrade the condensed tannin containing A-type linkage subunits (C4–C8 coupled C2–O–C7 linkage). These results suggest that the treatment of A. awamori can significantly improve the production of condensed tannin from litchi pericarp.

Highlights

Litchi (Litchi chinensis Sonn.), as a subtropical to tropical fruit with high commercial value, is widely planted in south China and Southeast Asian countries, as well as in African countries
Several hydrolytic enzymes produced by A. awamori, A. sojae and A. oryzae [18,19,20] likely released non-extractable polyphenols from litchi pericarp, increasing the extract recovery of the polyphenols
The hydrophobic products after the treatment of A. awamori exhibited higher DPPH radical scavenging activity than those treated with A. oryzae or A. sojae

Summary

Introduction

Litchi (Litchi chinensis Sonn.), as a subtropical to tropical fruit with high commercial value, is widely planted in south China and Southeast Asian countries, as well as in African countries. It has attractive red-colored pericarp tissue that contains a significant amount of polyphenols [1]. Solvent extraction of polyphenols from litchi pericarp has often been used, and a large amount of polyphenols (up to 50%) remain with the litchi pericarp [7,8] These non-extractable polyphenols are often conjugated to cell walls with a glycosidic bond or other interactions, making it hard to extract using aqueous organic solvent. Using microorganisms instead of enzymes has several advantages: (1) the production of enzymes can be induced in microorganisms that contain multiple enzymes for degrading various substrates; (2) it is an economic way to process plant-derived wastes; and (3) microorganism can sustainably produce the enzymes to release the conjugated polyphenols from cell walls

Methods

Results

Conclusion