Influence of Ethyl Caproate on the Size of Lipid Vesicles and Yeast Cells

Abstract

Ethyl caproate (EC) is a key flavor component of sake. Recently, in sake brewing, an effort has been underway to increase the content of aromatic components such as EC. However, the function of EC in yeast cells remains poorly understood. Therefore, we investigated the effects of EC using cell-sized lipid vesicles. We found that vesicle size decreases in a concentration-dependent manner when EC is contained in lipid vesicles. Furthermore, yeast experiments showed that a strain producing high quantities of EC in its stationary phase decreased in size during EC production. Given caproic acid’s (CA) status as the esterification precursor of EC in yeast, we also compared lipid vesicles containing CA with those containing EC. We found that CA vesicles were smaller than EC vesicles of the same concentration. These results suggest that EC production may function apparently to maintain cell size.

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

“…Therefore, our established strain is considered a highly productive strain compared with normal yeast strains. The growth curves and cell diameters have been reported before [ 5 ] and are now discussed in relation to the present data ( Figure 3 ).…”

“…Several different types of lipid vesicles (giant unilamellar vesicles and model membranes/liposomes) were prepared. A slightly modified version of the method of natural swelling from dry lipid films was used as outlined in our previous research [ 5 , 14 , 15 , 16 ]. Mixtures of lipids and flavors (i.e., DOPC, EC, CA, IA, and IAA) were dissolved in chloroform in a glass test tube under nitrogen gas.…”

“…As lipid vesicles have properties similar to cell membranes, artificial cell-sized lipid vesicles have been used as cell model membranes to reveal physicochemical properties of membranes that are important for life processes. Therefore, we have used a vesicle system formed by a single phospholipid component to study the physical—chemical effects of the flavor components [ 5 ]. Of note, good flavor components and their precursors influenced the behavior of the lipid vesicles, i.e., their size and fluidity, in a concentration-dependent manner.…”

“…Recently, we produced lipid vesicles containing EC and its precursor CA and found that these vesicles were small [ 5 ]. The diameter of vesicles affects several physicochemical properties [ 22 , 23 ].…”

“…The diameter of vesicles affects several physicochemical properties [ 22 , 23 ]. According to previous research, EC and CA should interact with lipid membranes [ 5 ]. We have postulated that different membrane properties correspond to different flavors; this could enable rapid detection and quantification of flavors in the future.…”