Size of Cells and Physicochemical Properties of Membranes are Related to Flavor Production during Sake Brewing in the Yeast Saccharomyces cerevisiae

Abstract

Ethyl caproate (EC) and isoamyl acetate (IA) are key flavor components of sake. Recently, attempts have been made to increase the content of good flavor components, such as EC and IA, in sake brewing. However, the functions of EC and IA in yeast cells remain poorly understood. Therefore, we investigated the effects of EC and IA using cell-sized lipid vesicles. We also investigated lipid vesicles containing EC and/or caproic acid (CA) as well as IA and/or isoamyl alcohol (IAA). CA and IAA are precursors of EC and IA, respectively, and are important flavors in sake brewing. The size of a vesicle is influenced by flavor compounds and their precursors in a concentration-dependent manner. We aimed to establish the conditions in which the vesicles contained more flavors simultaneously and with different ratios. Interestingly, vesicles were largest in a mixture of 50% of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with 25% EC and 25% CA or a mixture of 50% DOPC with 25% IA and 25% IAA. The impact of flavor additives on membrane fluidity was also studied using Laurdan generalized polarization. During the production process, flavors may regulate the fluidity of lipid membranes.

Genome Editing to Generate Sake Yeast Strains with Eight Mutations That Confer Excellent Brewing Characteristics

“…The clearest morphological changes were detected during the breeding of K7GE41. The K7GE41 cells became obviously larger ( Figure 7 C), in good agreement with the observation that the sake yeast strain producing a sweet ginjo aroma was large [ 32 ]. In addition, K7GE41 exhibited morphological changes, such as an increased proportion of cells with delocalized actin patches, increased G2 cells, and nuclear localization in mother cells ( Figure 7 C).…”

Quality Evaluation of Drinks Based on Liposome Shape Changes Induced by Flavor Molecules

“…Previously, our team had measured the concentration of such flavor molecules in sake . Therefore, the actual concentration was shown as an example of the concentration of such flavors that we reported previously; the actual concentration on the sake was 75, 16, and 100 μM for EC, IA, and IAA, respectively . This study is the first to report the dynamic shape changes induced by sake flavor molecules; 2 mM flavor solution was used with the same concentration and compared with glucose as the positive control solution.…”

“…The membrane properties are according to cell, organism, and membrane type . Studies of actual yeast cells reported that cell size differences corresponded to flavor production. ,, Morphological change of liposomes has received considerable attention recently, for example, the morphological change phase diagram is formed by the balance between the surface area and the encapsulation volume in the cell model. , It is well analyzed that the resulting excess surface area and deformation of liposomes due to osmotic pressure make the internal water escape to the surface to reduce the volume, increase the surface area of membrane lipids via isomerization, and so on. − Some studies have shown that membrane deformation occurs because the area of the membrane increases due to stimuli such as heat, and excess surface area is created while maintaining the internal volume. ,,, It has also been reported that liposome transformation is caused by a specific molecular interaction such as detergent , or polyphenol , with membrane lipid molecules. Recently, the impact of solvent selection on the microfluidic production of liposomes was reported .…”

“…Equal volumes of the lipid vesicle solution (6 μL) and flavor molecules or glucose solution (6 μL, 2 mM) were poured into a test tube and gently mixed by soft tapping. ,, The aforementioned mixed solution (6 μL) was placed in a silicon well (0.2 mm) in a glass slide and covered with a small coverslip . The changes in membrane morphology were observed using a phase-contrast microscope (Olympus BX-53, Japan) at RT …”

“…Dynamic shape changes by flavors such as EC, CA, IA, and IAA are attributed to the following reason. The reason is that the radius of flavor molecule-containing lipid vesicles is small in EC, CA, IA, and IAA, and these flavors change the fluidity of membranes. , Therefore, they may interact with membrane lipids and induce dynamic shape changes. This study investigated the dynamic shape changes of cell-sized liposomes induced by certain flavors for potential quality evaluation of drinks.…”