## 3 Results and Discussion
### Identification of Strain YHM-G  
After growing for 48 h at 30 \({}^{\circ}\)C on WL plates, the colonies of strain YHM-G were white, raised, with dry and rough surfaces and smooth edges and not easy to pick up (Supplementary Figure S1a). The WL medium had changed from blue to yellow where the yeast had grown (Supplementary Figure S1a). The cells of YHM-G observed under a microscope were rodlike with asexual budding reproduction occurring at one end of the cells without an endospore and mycelium (Supplementary Figure S1b). Thus, strain YHM-G exhibited the morphological and cellular structure of yeast. The physiological characteristics of strain YHM-G are shown (Supplementary Table S2). The sugar fermentations showed that strain YHM-G could use most types of sugar. Acid production and aerogenesis were observed when strain YHM-G was fermented with glucose, maltose, D-galactose and sucrose. Strain YHM-G only produced acid from D-maltose and aerogenesis from D-xylose and was unable to ferment L-rhamnose monohydrate, D-arabinose and lactose, as indicated by the lack of acid or gas production. Strain YHM-G was able to utilize glucose, maltose, D-galactose, sucrose, D-maltose, D-xylose, ethanol, glycerol, inulin, L-rhamnose monohydrate, D-arabinose and lactose but not D-raffinose, D-trehalose, mannose, D-ribose and D-sorbose. All nitrogen sources tested, including urea, ammonium sulfate, sodium nitrate, potassium nitrite, L-phenylalanine and L-lysine, were able to be used as the sole nitrogen source for growth. The YHM-G strain was positive for the indole test, methyl red test, starch hydrolysis test, citrate test and urea test, indicating that it was able to produce indole from tryptophan, acid from glucose and amylase to decompose starch and make use of sodium citrate or urea as a carbon source or nitrogen source for growth (Supplementary Table S2). Additionally, the Voges-Proskauer test, hydrogen sulfide test and gelatin liquification test were negative. From these physiological and biochemical characteristics, the YHM-G strain was preliminarily confirmed as _Hylopchichia_ sp. These results were helpful in understanding its metabolic activities, so that its metabolic pathway could play its corresponding functions. After searching the NCBI database, the ribosomal large subunit 26S rRNA gene D1/D2 domain fragment amplificated from YHM-G showed a 100% sequence similarity with a partial 26S rRNA gene sequence from _H. burtonii_ (CP024760.1, MH867400.1, KY107885.1, KY107883.1, KY107882.1, KY107877.1, HF952839.2, KC192660.1 and MK373312.1). According to branch clustering, strain YHM-G was closest to _H. burtonii_ CBS:2352 (KY107882.1) and _H. burtonii_ CBS:232.37 (MH867400.1) in the phylogenetic tree constructed using MEGA 7.0.14 software ([[https://www.megasoftware.net](https://www.megasoftware.net)]([https://www.megasoftware.net](https://www.megasoftware.net)), accessed on 17 July 2022) based on the neighbor-joining statistical method (Supplementary Figure S1c). Overall, strain YHM-G was identified as _H. burtonii_, according to the analysis of morphological, physiological and biochemical characteristics, and phylogenetic analysis. Although there is relatively little research on this strain, it has been reported to exist in the production process of many fermented foods, such as _Baijiu_[28], _Huangjiu_[28], ham [29], _Douchi_[30], Douban sauce [31], Kombucha [32], wine [33], traditional sourdough starters [34] and cocoa beans [35] through the use of traditional screening and high-throughput sequencing methods. Its presence has most often been reported in _Baijiu_, and there have been few studies on the role of this strain