Yeast Immobilization Systems for Alcoholic Wine Fermentations: Actual Trends and Future Perspectives

Abstract

Yeast immobilization is defined as the physical confinement of intact cells to a region of space with conservation of biological activity. The use of these methodologies for alcoholic fermentation (AF) offers many advantages over the use of the conventional free yeast cell method and different immobilization systems have been proposed so far for different applications, like winemaking. The most studied methods for yeast immobilization include the use of natural supports (e.g., fruit pieces), organic supports (e.g., alginate), inorganic (e.g., porous ceramics), membrane systems, and multi-functional agents. Some advantages of the yeast-immobilization systems include: high cell densities, product yield improvement, lowered risk of microbial contamination, better control and reproducibility of the processes, as well as reuse of the immobilization system for batch fermentations and continuous fermentation technologies. However, these methods have some consequences on the behavior of the yeasts, affecting the final products of the fermentative metabolism. This review compiles current information about cell immobilizer requirements for winemaking purposes, the immobilization methods applied to the production of fermented beverages to date, and yeast physiological consequences of immobilization strategies. Finally, a recent inter-species immobilization methodology has been revised, where yeast cells are attached to the hyphae of a Generally Recognized As Safe fungus and remain adhered following loss of viability of the fungus. The bio-capsules formed with this method open new and promising strategies for alcoholic beverage production (wine and low ethanol content beverages).

Matrices (re)loaded: Durability, viability, and fermentative capacity of yeast encapsulated in beads of different composition during long‐term fed‐batch culture

“…[26][27][28][29][30][31] Extended service life has been attributed to encapsulated cells' resistance to acids, 32,33 organic solvents, 34,35 ethanol, 36 and osmotic and thermal stress. 5 Encapsulated cells typically achieve higher product yield than planktonic cells as they divert less substrate to the formation of new biomass, 40,41 enabling them to more efficiently process feedstock. 5 Encapsulated cells typically achieve higher product yield than planktonic cells as they divert less substrate to the formation of new biomass, 40,41 enabling them to more efficiently process feedstock.…”

“…51 Continuous culture systems offer more precise control over growth conditions, and this can translate into higher yields. 41 To fill these knowledge gaps, glucose consumption and ethanol production by S. cerevisiae were monitored over the course of 7 weeks, comparing the performance of cells in planktonic culture with cells encapsulated as~4 mm "beads" composed of four different matrices. 56 Thus, while multiple studies suggest that encapsulated cells could be re-used over several weeks, few 57,58 have explored whether and how different encapsulation matrices impact fermentation capacity and related parameters over longer time periods.…”

“…37,38 These features are likely to be consequences of altered cell wall and plasma membrane composition following encapsulation, 39 and possibly also protection from shear forces afforded by the encapsulating matrix. 5 Encapsulated cells typically achieve higher product yield than planktonic cells as they divert less substrate to the formation of new biomass, 40,41 enabling them to more efficiently process feedstock.…”

“…56 Thus, while multiple studies suggest that encapsulated cells could be re-used over several weeks, few 57,58 have explored whether and how different encapsulation matrices impact fermentation capacity and related parameters over longer time periods. 41 To fill these knowledge gaps, glucose consumption and ethanol production by S. cerevisiae were monitored over the course of 7 weeks, comparing the performance of cells in planktonic culture with cells encapsulated as~4 mm "beads" composed of four different matrices. To simulate industrial fermentation, a fed-batch system was used instead of the continuously fed system like that described by Nagarajan et al We evaluated parameters related to bead resilience (Young's modulus, viscosity, size, and mass) and biological parameters related to fermentation capacity (ethanol yield, cell number/viability, and thermotolerance).…”

Physical confinement impacts cellular phenotype within living materials

“…The previous studies on effects of physical confinement in a calcium alginate matrix indicate changes in cellular physiology of yeast. 31,32 Though, a molecular investigation of cells was not in the scope of the present study, it would be very valuable to understand underlying molecular mechanisms responsible for phenotypic differences in LMs for their development as a technology of the future.…”