Microbial Diversity of Marula Wine during Spontaneous Fermentation

Marula wine is produced from ripe fruits of the <i>Sclerocarya birrea</i> subspecies <i>caffra</i> tree through spontaneous fermentation. A few culture-based studies have shown that the fermentation is largely driven by yeasts, although, in the early stages, some lactic acid bacteria (LAB) and acetic acid bacteria may be detected. Some of the microbes may produce undesirable metabolites that lead to the spoilage and short shelf life of the wine. However, there is generally limited information on the microbial composition and its contribution to the chemical characteristics of the resultant marula wine. The aim of this study was to characterise the microbial population of marula wine from different localities in the Limpopo province, South Africa. MALDI-TOF and amplicon sequencing technique were used to identify microbial strains and to determine their diversity and changes in the different stages of fermentation. The phylogenetic relationships of LAB and <i>S. cerevisiae</i> were analysed using multilocus sequence typing. Bacterial species that were common in the different marula wines included <i>Gluconobacter oxydans</i>, <i>Lactiplantibacillus plantarum</i>, <i>Levilactobacillus brevis</i>, <i>Lacitilactobacillus nagelii</i>, <i>Lentilactobacillus kefiri</i> and <i>Lentilactobacillus parabuchneri</i>, and the yeasts were <i>Hanseniaspora guiliermondii</i>, <i>Saccharomyces cerevisiae</i>, <i>Rhodotorula mucilaginosa</i> and <i>Pichia kudriavzevii</i>. The MLST data indicated common microbiota from different marula wines with low intraspecific diversity, suggesting that the LAB and <i>S. cerevisiae</i> strains that are mainly responsible for the spontaneous fermentation of marula wine are similar irrespective of the geographical differences and production preferences.