Oenococcus oeni UNQOe19 is a native strain isolated from a Patagonian pinot noir wine undergoing spontaneous malolactic fermentation. Here, we present the 1.83-Mb genome sequence of O. oeni UNQOe19, the first fully assembled genome sequence of a psychrotrophic strain from an Argentinean wine.

Malolactic fermentation (MLF) is a biological process of deacidification of wines that may also help to increase the microbiological stability of the product and to enhance its sensorial attributes, in particular its aromatic profile. MLF can occur spontaneously due to the presence of indigenous bacteria in the environment of fermented beverages such as wines and ciders. However, the inoculation of lactic acid bacteria (LAB) starter cultures could prevent potential losses and standardize the process. The industrial-scale production of these starter cultures requires cost-effective, sustainable, and feasible approaches. A possible approach to acquire bacterial biomass, while addressing waste disposal concerns, is the use of by-products from the apple juice industry, such as apple pomace. Moreover, to ensure the long-term viability and activity of starter cultures, appropriate preservation methodologies need to be developed. Thus, the aim of the present study was to evaluate the growth of two Lactiplantibacillus plantarum strains, UNQLp11 and UNQLp155, in supplemented apple pomace and to optimize the preservation conditions. Cultures were either frozen or freeze dried (trehalose (20% m/v) as a protective agent, potassium phosphate buffer (pH 7), and a combination of trehalose and buffer), and then cell viability and malolactic activity were analyzed under wine stress conditions. Notably, the combination of phosphate buffer at pH 7.0 and trehalose emerged as the most effective preservation strategy for freeze drying, exhibiting enhanced viability and malic acid consumption for the two strains evaluated. These findings underscore the inexpensive and sustainable viability of using a semi-solid medium formulated with apple pomace for LAB biomass production and subsequent preservation.

The Lacticaseibacillus paracasei UNQLpc 10 strain was isolated from a Malbec wine produced in North Patagonia, Argentina, and identified by 16S rRNA gene sequencing. The aim of this work was to obtain the fully assembled genome of the UNQLpc 10 strain, analyze its structure, and evaluate the possible functions of the predicted genes with regard to its oenological potential as a malolactic starter. UNQLpc10 is the first whole assembled genome of an oenological strain of Lcb. paracasei reported in databases. This information is of great interest inexpanding the knowledge of diversity of oenological lactic acid bacteria and in searching for new candidate species/strains to design starter cultures. The in silico genome-wide analysis of UNQLpc 10 confirms the existence of genes encoding enzymes involved in the synthesis of several metabolites of oenological interest, and proteins related to stress responses. Furthermore, when UNQLpc 10 was incubated in synthetic wine, it exhibited a very good survival and L-malic acid consumption ability.

The by-products of the food industry are an economic alternative as a source of nutrients to obtain biomass. At the same time, theiruse could solve the environmental problem related to their disposal, which is highly polluting due to their elevated biochemical oxygen demand. In this work, we seek to optimize the production of cellular biomass of two native Patagonian strains of Lactiplantibacillus plantarum (UNQLp 11 and UNQLp155), selected for its oenological and technological properties, using apple pomace (AP), a residue from the juice and cider industry. The supplementation of AP with yeast extract, salts, and Tween 80 (sAP), proved to maintain the growth of the Lpb. plantarum strains, similar to the commercial medium used to grow LAB (De Man, Rogosa, Sharpe, MRS). Cultures grown in sAP medium showed good tolerance to wine conditions (high ethanol content and low pH), demonstrated by its ability to consume L-malic acid. The subsequent inoculation of these cultures in sterile wines (Merlot and Pinot noir) was carried out at laboratory scale, evaluating cell viability and L-malic acid consumption for 21 days at 21 °C. Cultures grown in sAP media showed a similar performance to MRS media. Thus, sAP media proved to be a suitable substrate to grow oenological Lpb. plantarum strains where cultures (with high size inoculums) were able to drive malolactic fermentation, with an L-malic acid consumption higher than 90%.