*Lactobacillus plantarum***, a New Biological Tool to Control Malolactic Fermentation: A Review and an Outlook**

#### **Sibylle Krieger-Weber 1,\*, José María Heras 2 and Carlos Suarez 2**


Received: 26 February 2020; Accepted: 1 April 2020; Published: 7 April 2020

**Abstract:** Malolactic fermentation (MLF) in wine is an important step in the vinification of most red and some white wines, as stands for the biological conversion of l-malic acid into l-lactic acid and carbon dioxide, resulting in a decrease in wine acidity. MLF not only results in a biological deacidification, it can exert a significant impact on the organoleptic qualities of wine. This paper reviews the biodiversity of lactic acid bacteria (LAB) in wine, their origin, and the limiting conditions encountered in wine, which allow only the most adapted species and strains to survive and induce malolactic fermentation. Of all the species of wine LAB, *Oenococcus oeni* is probably the best adapted to overcome the harsh environmental wine conditions and therefore represents the majority of commercial MLF starter cultures. Wine pH is most challenging, but, as a result of global warming, *Lactobacillus* sp. is more often reported to predominate and be responsible for spontaneous malolactic fermentation. Some *Lactobacillus plantarum* strains can tolerate the high alcohol and SO2 levels normally encountered in wine. This paper shows the potential within this species for the application as a starter culture for induction of MLF in juice or wine. Due to its complex metabolism, a range of compositional changes can be induced, which may positively affect the quality of the final product. An example of a recent isolate has shown most interesting results, not only for its capacity to induce MLF after direct inoculation, but also for its positive contribution to the wine quality. Degrading hexose sugars by the homo-fermentative pathway, which poses no risk of acetic acid production from the sugars, is an interesting alternative to control MLF in high pH wines. Within this species, we can expect more strains with interesting enological properties.

**Keywords:** malolactic fermentation; *Lactobacillus plantarum*;*Oenococcus oeni*; facultative hetero-fermentative; starter cultures
