Glutathione fermentation by Millerozyma farinosa using spent coffee grounds extract and seawater

Abstract Large amounts of spent coffee grounds are produced daily and represent a global agricultural waste issue. Therefore, conversion of spent coffee grounds to fine chemicals by microorganisms is an attractive biorefinery approach. The valuable tripeptide, glutathione, because of its antioxidant activity, is typically produced in industrial processes by Saccharomyces cerevisiae. However, S. cerevisiae growth is inhibited by caffeine present in spent coffee grounds. In this report, a caffeine-resistant glutathione-producing yeast Millerozyma farinosa was identified. M. farinosa was originally obtained from miso paste and has not been used previously to produce glutathione. M. farinosa cell growth and cellular glutathione synthesis were enhanced by the addition of a spent coffee grounds extract to the culture medium. The addition also showed two-fold increase in overall glutathione production with an equal cell growth by M. farinosa cultured in artificial seawater because this yeast is salt tolerant.