Sherry wine is a pale-yellowish dry wine produced in Southern-Spain which features are mainly due to biological aging when the metabolism of biofilm-forming yeasts (flor yeasts) consumes ethanol (and other non-fermentable carbon sources) from a previous alcoholic fermentation, and produces volatile compounds such as acetaldehyde. To start aging and maintain the wine stability, a high alcohol content is required, which is achieved by the previous fermentation or by adding ethanol (fortification). Here, an alternative method is proposed which aims to produce a more economic, distinctive Sherry wine without fortification. For this, a flor yeast has been pre-acclimatized to glycerol consumption against ethanol, and later confined in a fungal-based immobilization system known as “microbial biocapsules”, to facilitate its inoculum. Once aged, the wines produced using biocapsules and free yeasts (the conventional method) exhibited chemical differences in terms of acidity and volatile concentrations. These differences were evaluated positively by a sensory panel. Pre-acclimatization of flor yeasts to glycerol consumption was not successful but when cells were immobilized in fungal pellets, ethanol consumption was lower. We believe that immobilization of flor yeasts in microbial biocapsules is an economic technique that can be used to produce high quality differentiated Sherry wines.

Reticulitermes grassei is a subterranean termite species that forages on woody structures of the Iberian Peninsula, and is often a building and crops pest. A total of 23 microorganisms associated with the activity of R. grassei were isolated from colonized ecosystems in southern Spain. They were morphologically and molecularly characterized, with fungi being the most prevalent ones. The fungi showed high values of optimum growth temperature, suggesting that they could be able to survive and develop in warm regions. Their cellulolytic activity was tested in carboxymethylcellulose (CMC) agar, concluding that all fungal isolates produce cellulases, and the enzymatic index (EI) was revealed in CMC agar with Gram’s iodine solution, with Penicillium citrinum showing the highest EI and Trichoderma longibrachiatum the highest mycelial growth rate on CMC. A preliminary microorganism dispersion assay was carried out with the termites, concluding that these insects may have a positive influence on fungal dispersion and the subsequent colonization of new substrates. Our study suggests that fungi associated with R. grassei may potentially be of interest in biotechnological fields such as biofuel production and the food industry.

Non-Saccharomyces yeasts play a significant role in winemaking, offering unique benefits and contributing to wine complexity and varied and desirable aromatic profiles. This work focuses on the sensory improvement of Pedro Ximénez white wines using selected strains of Wickerhamomyces anomalus isolated from biologically aged wines. Chemical and microbiological analyses confirmed the implantation of W. anomalus; these yeast strains appear to displace indigenous non-Saccharomyces species in the must and produce large amounts of ethyl acetate and lower ethanol content. Wines made with W. anomalus strains were judged negatively by the tasting panel due to a nail polish/varnish odor and a strong, bitter taste; however, when these wines were blended with wine normally produced by spontaneous fermentation, the judges rated them positively, highlighting fruity aromas not detected under other conditions. These results conclude that W. anomalus strains isolated from biologically aged wines could be useful for modulating the sensory profile of white wines. Moreover, their use in combination with other yeasts or in immobilized form could improve the results obtained and avoid the blending process. The high yield of ethyl acetate produced by these strains could be of interest as an alternative to current methods of producing this compound, including the use of these wines for the production of quality vinegar.

This work focuses on the production of a white wine with a specific organoleptic profile by means of sequential fermentation using immobilized yeast in a system known as “microbial biocapsules”. Three fermentation conditions were created: sequential fermentation with immobilized yeast (SqFMB) employing a matrix composed by Aspergillus oryzae (pellet-forming fungus recognized as GRAS), sequential fermentations with non-immobilized yeast cells (SqF), and a control of spontaneous fermentation (SpF). To carry out these fermentations, Pedro Ximénez grape must was used and two non-Saccharomyces yeast strains, Debaryomyces hansenii LR1 and Metschnikowia pulcherimma Primaflora, and the Saccharomyces cerevisiae X5 strain were used. The wines produced were subjected to microbiological and chemical analyses in which metabolites that positively influence the wine profile, such as 1,1-diethoxyethane and decanal, are only produced in the SqFMB condition, and others, like nonanal, were detected in higher concentrations than in SqF and SpF. Microbiological analyses show that less non-Saccharomyces yeasts were isolated in the SqFMB condition than in SqF, which indicates an efficiency in the inoculation and removal method proposed. These results conclude that microbial biocapsules seem to be a good yeast carrier for wine elaboration; however, modulation of some variables like yeast concentration inocula, the employment of preadaptation methods or the use of yeast species with higher fermentative power need to be tested to improve the novel methodology.

The Criaderas and Solera system represents one of the most sophisticated aging methodologies in winemaking, producing distinctive Sherry wines through dynamic blending and biological aging processes. This traditional Spanish system, combined with the unique metabolic activities of flor yeast (Saccharomyces cerevisiae), creates wines of exceptional complexity and consistency. This comprehensive review synthesizes current literature on the Criaderas and Solera system, focusing on biological aging mechanisms, flor yeast dynamics, industrial applications, and contemporary challenges. Recent advances in genomic, proteomic and metabolomic studies of flor yeasts have been analyzed, alongside modern analytical approaches to the characterization of Sherry wine. The Criaderas and Solera system enables consistent wine quality through fractional blending across multiple aging levels. Flor yeasts exhibit specialized metabolic adaptations, including enhanced ethanol oxidation capacity, biofilm formation abilities, and stress resistance mechanisms. Modern applications extend beyond traditional winemaking to include biotechnological uses, immobilization techniques, and sustainable production methods. Current challenges include climate change impacts, maintaining genetic diversity, adapting to new technologies and meeting evolving consumer preferences. The integration of traditional knowledge with modern biotechnology offers promising opportunities for optimizing Sherry production. Understanding flor yeast ecology and metabolic pathways provides insights for developing innovative applications while preserving the authenticity of this centuries-old winemaking tradition.

This study investigates nitrogen metabolism during the middle of the second fermentation in stopped bottles of sparkling wine, focusing on two flor Saccharomyces cerevisiae yeast strains (G1 and N62) isolated from the velum of biologically aged wine. Nitrogen compounds, including amino acids, biogenic amines, and ammonium chloride, were quantified, revealing strain-specific differences in nitrogen utilization and production. Proteomic analysis identified 1053 proteins, with 127 showing significant differences between strains. Strain G1 demonstrated enhanced cell wall remodeling and prioritized nitrogen conservation via arginine and lysine biosynthesis, while strain N62 exhibited increased translational activity and alternative carbon utilization pathways. Notably, strain N62 produced higher concentrations of biogenic amines (putrescine and tyramine), likely due to its greater decarboxylation capacity. Principal Component Analysis (PCA) highlighted clear differentiation in the nitrogen compound profiles across the base wine and wines inoculated with the two strains. The proteome of strain N62 showed increased mitochondrial activity and TCA cycle involvement, facilitating faster fermentation (27 days vs. 52 days for G1), growth (46 × 10⁶ cells/mL vs. 21 × 10⁶ cells/mL for G1) and cell viability (4 × 10⁶ cells/mL vs. 0.7 × 10⁶ cells/mL for G1). These findings suggest that yeast strain selection significantly influences nitrogen metabolism and potentially aroma profiles and and fermentation dynamics in sparkling wine production. Understanding these metabolic adaptations provides valuable insights for optimizing yeast performance to enhance wine quality and preserve regional characteristics.