## 1 Introduction  
Malolactic fermentation (MLF) plays a vital role in winemaking [1, 2, 3]. It is completed by a kind of malolactic bacteria (MLB) that can metabolize L-malic acid to L-lactic acid. MLF can be started by MLB, which, from the surface of the grape, it is not always successful [4]. This is due to wine's poor and complex habitat conditions (high ethanol, low pH, high SO\({}_{2}\)). It results in the inhibition or even inactivation of wild LAB, thus affecting the progress of MLF. Based on the highly genetic polymorphisms and mutants of _Oenococcus oeni_, the starter of commercial MLB is mostly _O. oeni_[5]. Usually, _O. oeni_ is the dominant flora in wine at the beginning of spontaneous MLF. However, due to the influence of climate change, the ethanol of wines is getting higher and higher. _O. oeni_ strains cannot survive well in high-ethanol wines, which make the start and finish of MLF become more and more difficult. More and more research found that _Lactiplantibacillus plantarum_ can strongly tolerate high ethanol [6, 7, 8]. Therefore, isolating and screening some potential _L. plantarum_ strains have great significance for the wine industry.  
_L. plantarum_ is a common MLB in wines. For its good fermentation and safety characteristics, _L. plantarum_ is widely used in food fermentation [9, 10, 5]. _L. plantarum_ has good resistance to environment stress, such as salt, acid, and ethanol stress [12]. _L. plantarum_ may survive in wine environments with up to 17% (\(v/v\)) ethanol, and it has numerous benefits to MLF and wines compared with _O. eeni_, including fewer nutritional needs and faster growth rate and bacteriocin metabolism [6; 7; 13; 14; 15]. It helps improve wine color and is an anti-browing agent for wine [16; 17]. _L. plantarum_ is rich in various enzymes, including esterase, citrate lyase, \(\beta\)-glucosidase, proline aminopeptidase, and phenolic acid decarboxylase (PAD), and due to the enzyme activity, some strains alter the chemical composition of wine by metabolizing synthetic aroma precursors [18]. This brings more possibilities for MLF. Esterases can help synthesize or hydrolyze esters and can contribute to wine aroma [19]. \(\beta\)-Glucosidase promotes glycoside hydrolysis and enriches wine aroma substances. PAD is associated with phenolic acid formation. The presence of \(\beta\)-glucosidase and phenolic acid decarboxylase could allow this species to be used in the future to alter the aroma profile of wine [20]. Tannase can hydrolyze substrates to produce caffe acid and quinic acid. It also has substances for chemical stabilization [21]. At the same time, numerous research results show that _L. plantarum_ has certain antibacterial activities. Some organic acids and proteins produced by metabolism can act as antibacterial molecules to antagonize other harmful microorganisms [22; 23; 24; 25]. Therefore, as a new type of MLF starter, _L. plantarum_ has important value for MLF in winemaking.  
In this research, high-ethanol-tolerant _L. plantarum_ strains were isolated and identified. Stress tolerance, \(\beta\)-D glycosidase activity, enological characteristics, and the biogenic amines produce of the isolates were tested to screen potential MLF starters for high-ethanol wines.