Gabriel Alejandro Rivas

Malolactic fermentation conducted by lactic acid bacteria is essential for enhancing wine’s sensory qualities. Although this process can occur spontaneously through the action of native lactic acid bacteria (LAB) from the grapes and cellar, it carries risks such as increased volatile acidity, consumption of residual sugars, and the formation of undesirable metabolites like biogenic amines. This study evaluated the oenological potential of three innovative native malolactic fermentation starters (MLFS) on a pilot scale, aiming to offer local wineries cost-effective MLFS with native LAB strains. Alcoholic fermentation of Malbec grapes was carried out using a commercial yeast starter, followed by a sequential inoculation of native malolactic starters formulated with (i) mesophilic Lactiplantibacillus plantarum UNQLp11 and Oenococcus oeni UNQOe73.2, both from the Province of Río Negro; (ii) psychrotrophic Lentilactibacillus hilgardii UNQLh1.1 and Oenococcus oeni UNQOe19, both from the Province of Río Negro; (iii) mesophilic Lactiplantibacillus plantarum UNQLp1001, from the Province of Buenos Aires; and (iv) a commercial malolactic started, which served as a control. Malic acid was consumed by all starters. RAPD-PCR using M13 primer showed the native LAB’s capability for implantation in wine. A sensory analysis revealed distinct profiles for each formulation, despite having been inoculated at the end of the same alcoholic fermentation. These MLFS could replace imports, enhancing the region’s unique terroir.

Beer lees (BL), a by-product of beer production, consist mainly of dead yeast cells with potential nutritional value. On the other hand, yeast extract (YE), obtained through the lysis of yeast cells, is commonly used as a nutrient-rich supplement for the growth of fastidious microorganisms such as lactic acid bacteria (LAB). However, YE is a high-cost ingredient. Therefore, the aim of this study was to optimize the use of BL as a low-cost alternative source of YE through different lysis treatments, evaluating its suitability to support the growth of UNQLpc 10 and UNQLp 11 strains in a whey permeate (WP)-based medium. Growth kinetics and cell viability were compared with those obtained in MRS broth. The best results were observed with sonicated BL, up to 10 logarithmic units, which supported LAB growth comparable to MRS. Although autolyzed BL promoted lower bacterial growth than sonicated BL, it showed greater cell disruption and higher levels of nitrogen, proteins, and amino acids (5.32%, 26.0%, and 277 nM, respectively). Additionally, autolyzed BL exhibited lower concentrations of reducing sugars and a higher presence of Maillard reaction products, as indicated by colorimetric analysis. These changes, which may be related to the formation of Maillard reaction products during the autolysis process, could have negatively affected the nutritional quality of the extract and, thus, reduced its effectiveness as a bacterial growth promoter.

Argentina ranks worldwide among the top ten wine producers, known for its diverse terroirs and Malbec as its emblematic varietal. Typically, the winemaking process involves alcoholic fermentation, led by yeasts, and malolactic fermentation (MLF), primarily driven by lactic acid bacteria (LAB). Oenococcus oeni and Lactiplantibacillus plantarum are recognised as the best-adapted LAB species for this process. Our previous research focused on a winery located in the southwest of Buenos Aires Province, a scarcely studied re-emerging region of Argentina, which showed a low relative abundance of LAB and incomplete MLF in various vintages. The current study involved the isolation, identification, typing, and use of native strains from the above-mentioned region to formulate a malolactic fermentation starter (MLFS) and to evaluate the strains’ malolactic performance at pilot-scale, implantation capacity and impact on wine aromatic profiles using HS-SPME-GC-FID/MS. Two selected autochthonous strains (Lpb. plantarum UNQLp1001 and a O. oeni UNQOe1101) from the re-emerging region successfully implanted in Malbec wine, achieving faster and more efficient MLF compared to spontaneous MLF. Moreover, the MLFS seems to have influenced the aromatic profile, reducing relative concentrations of alcohols, contributing to the decrease in the bitter and herbaceous notes, and increasing some esters (ethyl acetate, 2-phenethyl acetate, ethyl octanoate), that could enhance floral and fruity, notes. Expanding the availability of candidate strains to formulate native MLFS is a crucial technological tool for the wine industry. Thus, we propose the use of Lpb. plantarum UNQLp1001 and O. oeni UNQOe1101 as potential MLFS in Malbec wines from somewhat similar wine-producing regions. Additionally, the local winery can access a cost-effective MLFS with native LAB strains, enabling a more controlled MLF that preserves regional typicity. Moreover, these strains could enable technology transfer, potentially becoming the first malolactic starters in the region.

Argentina se ubica entre los países “top 10” del planeta en lo referido a industria vitivinícola, siendo el 7º productor mundial de vino, el 8º exportador, y el 9º consumidor. Las regiones vitivinícolas tradicionales han sido extensamente estudiadas mediante técnicas que dependen del cultivo de microorganismos en el laboratorio, y en menor medida por técnicas independientes del mismo. Sin embargo, regiones que han estado relegadas por razones políticas, económicas y sociales, hoy son reconocidas como re-emergentes a nivel productivo, pero se encuentran estudiadas muy pobremente o permanecen sin estudiar. La provincia de Buenos Aires se ubica como una región re-emergente de interés socio-económico y cultural debido a su crecimiento en vitivinicultura durante los últimos 20 años. El objetivo del presente trabajo consistió en estudiar por técnicas dependientes e independientes de cultivo, una muestra de mosto de la vendimia 2018 de una bodega bonaerense, con especial énfasis en la comparación de las bacterias del ácido láctico (BAL) detectadas mediante ambos tipos de estudios. Se lograron obtener 6 cepas de BAL: 4 cepas de Lactiplantibacillus plantarum, 1 cepa de Enterococcus mundtii y 1 cepa de Enterococcus durans. La caracterización inicial de las cepas de Lpb. plantarum mediante el estudio de sus cinéticas de crecimiento y resistencia al etanol, permitió sugerirlas como posibles candidatos para la futura formulación de iniciadores de fermentación maloláctica (FML). Por otra parte, mediante la secuenciación masiva del gen 16S rRNA, se observó que los filos más abundantes fueron Proteobacterias, Actinobacterias y Firmicutes, sin embargo, no se lograron encontrar miembros del orden Lactobacillales, al que pertenecen las BAL. Los resultados del presente trabajo refuerzan la necesidad de realizar análisis integrales que permitan incrementar la sensibilidad de detección de BAL en muestras de mosto y vino de estas regiones vitivinícolas re-emergentes. Estudios como el presente, podrían resultar relevantes para nuestro país, ya que pueden contribuir con los productores a identificar y resolver inconvenientes, y aportar con sugerencias para mejorar el proceso fermentativo a fin de obtener vinos de mayor calidad e incrementar su valor agregado.

The spontaneous malolactic fermentation (MLF) in a centenary winery from Patagonia, Argentina, is conducted by predominantly mesophilic Oenococcus oeni and Lactiplantibacillus plantarum. In this region, MLF takes place from 14 to 4 °C, leading to heat cellars incurring in higher costs and non-sustainable practices. Previously, psychrotrophic strains of O. oeni had been obtained from a Patagonian wine. The goal of this work was to identify the Lactobacillaceae microbiota related to low-temperature MLF and assess their contribution. Nine sychrotrophicc Lentilactibacillus hilgardii strains were identified by sequencing the 16S rRNA gene, and the strains typified by RAPD-PCR. All strains consumed L-malic acid at 4 and 10 °C in sterile wine. The selected UNQLh1.1 strain revealed implantation capacity and L-malic acid consumption at 4 and 10 °C in the presence of the native microbial consortium. Furthermore, the histidine decarboxylase (hdc) gene was not detected in any of the Len. hilgardii strains. The prevalence of Len. hilgardii under low-temperature conditions represents a novelty compared to previous findings of LAB diversity in the MLF of Patagonian wines. The native Patagonian psychrotrophic Len. hilgardii strains are a new player in fermentations conducted at low temperatures with the potential to be used as a sustainable MLF starter.

Winemaking is a complex process involving two successive fermentations: alcoholic fermentation, by yeasts, and malolactic fermentation (MLF), by lactic acid bacteria (LAB). During MLF, LAB can contribute positively to wine flavor through decarboxylation of malic acid with acidity reduction and other numerous enzymatic reactions. However, some microorganisms can have a negative impact on the quality of the wine through processes such as biogenic amine production. For these reasons, monitoring the bacterial community profiles during MLF can predict and control the quality of the final product. In addition, the selection of LAB from a wine-producing area is necessary for the formulation of native malolactic starter cultures well adapted to local winemaking practices and able to enhance the regional wine typicality. In this sense, molecular biology techniques are fundamental tools to decipher the native microbiome involved in MLF and to select bacterial strains with potential to function as starter cultures, given their enological and technological characteristics. In this context, this work reviews the different molecular tools (both culture-dependent and -independent) that can be applied to the study of MLF, either in bacterial isolates or in the microbial community of wine, and of its dynamics during the process.

Argentina is the fifth world-wide wine producer, with an area of emerging importance in the Southwest of Buenos Aires Province, where climatic conditions are rather challenging. We studied the variations in soil and wine bacterial diversity through three consecutive vintages, and how climatic conditions affected said diversity. During the years of our study there were two harsh climatic events, a prolonged drought that extended over two vegetative periods, and an unseasonable spring frost in 2017. We found that the bacterial diversity reacted to these climatic events, given that there was a shift in the taxa exclusive to soil and wine, and shared by both, through time. Our results show a core of microorganisms in soil as well as in wine, belonging to different phyla that are conserved across the vintage years. A trend to an enrichment in Actinobacteria was detected in soil samples, whereas a high relative abundance of the Acetobacteraceae family and a scarcity of Lactic Acid Bacteria (LAB) were detected in the wine samples. We believe our results contribute to a better understanding of the impact of climatic conditions on the soil and wine microbiota, and can provide vintners with valuable knowledge for improving their wine production.