Jellyfish Aequorea victoria green fluorescent protein (GFP) and its variants are widely used in many biological studies. A lot of reports related in GFP has been appeared in this decade as a useful probe. For example, to prove a protein localization, transcriptional level, molecular interactions, etc. On the other hand, there are not so many reports using GFP in applicational reports like bioprocess. In late years, enhanced GFP (EGFP) was able to be displayed as active form on the surface of yeast Saccharomyces cerevisiae. This "arming yeast" is expected to be used in practical study and industry. However, it had better to be improved that fluorescence of displayed EGFP is not stable because cell surface contacts medium whose pH is changed drastically depending on growtb phase. We aimed to inhibit the photobleaching of EGFP on the cell surface as long as possible and it was succeeded by using HEPES in the medium.