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Biomolecules. 2019 Sep 2;9(9). pii: E439. doi: 10.3390/biom9090439.

Integrated Approaches to Reveal Genes Crucial for Tannin Degradation in Aureobasidium melanogenum T9.

Author information

1
College of Chemistry & Environmental Engineering, Shandong University of Science & Technology, Qingdao 266510, China.
2
Laboratory for Marine Fisheries and Aquaculture-Qingdao National Laboratory for Marine Science and Technology, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China.
3
College of Science, China University of Petroleum, Qingdao 266580, China.
4
Development & Reform Bureau, West Coast New Area, Qingdao 266000, China.
5
Key Laboratory of Sustainable Development of Polar Fishery, Ministry of Agriculture and Rural Affairs, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China. spirit87@163.com.
6
Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310014, China.

Abstract

Tannins biodegradation by a microorganism is one of the most efficient ways to produce bioproducts of high value. However, the mechanism of tannins biodegradation by yeast has been little explored. In this study, Aureobasidium melanogenum T9 isolated from red wine starter showed the ability for tannins degradation and had its highest biomass when the initial tannic acid concentration was 20 g/L. Furthermore, the genes involved in the tannin degradation process were analyzed. Genes tan A, tan B and tan C encoding three different tannases respectively were identified in the A. melanogenum T9. Among these genes, tan A and tan B can be induced by tannin acid simultaneously at both gene transcription and protein expression levels. Our assay result showed that the deletion of tanA and tanB resulted in tannase activity decline with 51.3 ± 4.1 and 64.1 ± 1.9 U/mL, respectively, which is much lower than that of A. melanogenum T9 with 91.3 ± 5.8 U/mL. In addition, another gene coding gallic acid decarboxylase (gad) was knocked out to better clarify its function. Mutant Δgad completely lost gallic acid decarboxylase activity and no pyrogallic acid was seen during the entire cultivation process, confirming that there was a sole gene encoding decarboxylase in the A. melanogenum T9. These results demonstrated that tanA, tanB and gad were crucial for tannin degradation and provided new insights for the mechanism of tannins biodegradation by yeast. This finding showed that A. melanogenum has potential in the production of tannase and metabolites, such as gall acid and pyrogallol.

KEYWORDS:

Aureobasidium melanogenum; Tannase; gallic acid decarboxylase; tannins biodegradation

PMID:
31480670
DOI:
10.3390/biom9090439
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