A validated strategy to design efficient fermentation-industrial processes: agave spirit production

Enhancing Mezcal Production Efficiency by Adding an Inoculant of Native Saccharomyces cerevisiae to a Standardized Fermentation Must

All traditional mezcal producers use artisan methods to produce mezcal. The low technological development in the elaboration processes results in low yield and high residual sugar concentration. First, this work optimized the concentration of initial sugars and yeast-assimilable nitrogen (YAN) in Agave durangensis juice fermentation at the laboratory level. A yield near 0.49 g EtOH/g sugar and a productivity of 1.54 g EtOH/L*h was obtained with an initial sugar concentration of 120 g/L and a YAN concentration of 0.227 g/L. Only Saccharomyces cerevisiae was found after 24 h of incubation at laboratory level, using MALDI-TOF identification. Agave durangensis heads crushed by the artisan process were used to test the inoculant performance. A mezcal yield of 11.6 kg agave/L of mezcal was obtained using the S cerevisiae inoculant and nitrogen addition, which was significantly different (p < 0.05) from other treatments. The population dynamics during fermentation were analyzed through isolation and identification using MALDI-TOF. Several yeast species (Pichia kluyveri, Torulaspora delbrueckii, Zygosaccharomyces bailii, and Saccharomyces cerevisiae) were found at the beginning of fermentation. Nonetheless, only S. cerevisiae was found at the end of fermentation. The implantation of the inoculant used was confirmed through the comparative analysis of amplification patterns of the GTG5 microsatellite of the strains identified as S. cerevisiae, finding that the inoculated strain proportion was greater than 80% of the yeast population. A technological alternative to increase the efficiency of the process is combining the addition of YAN and the inoculation of the native S. cerevisiae, which was isolated from artisan alcoholic fermentation of agave to produce mezcal.

A novel strategy to construct multi-strain starter cultures: an insight to evolve from natural to directed fermentation

Some biotechnological strategies have succeeded in the attempt to imitate natural fermentation, and bioprocesses have been efficiently designed when the product is the result of a unique biological reaction. However, when the process requires more than one biological reaction, few bioprocesses have been successfully designed because the available tools to construct multi-strain starter cultures are not yet well defined. In this work, a novel experimental strategy to construct multi-strain starter cultures with selected native microorganisms from natural fermentation is proposed. The strategy analyses, selects, and defines the number and proportion of each strain that should form a starter culture to be used in directed fermentations. It was applied to evolve natural fermentation to directed fermentation in distilled agave production. The results showed that a starter culture integrated by Kluyveromyces marxianus, Clavispora lusitaniae, and Kluyveromyces marxianus var. drosophilarum in proportions of 35, 32, and 33%, respectively, allows obtaining fermented agave juice containing a 2.1% alcohol yield and a distilled product with a broad profile of aromatic compounds. Hence, the results show, for the first time, a tool that addresses the technical challenge for multi-strain starter culture construction, offering the possibility of preserving the typicity and genuineness of the original traditional product.