Extraction of Glutathione Involved in Yeast Fermentation as Co-product of Second Generation Bioethanol from Oil Palm Empty Fruit Bunch

Abstract

The production of second-generation bioethanol in general consists of four steps: pretreatment, hydrolysis, sugar fermentation, and purification. In part of fermentation, yeast Saccharomyces cerevisiae is commonly used to convert glucose into ethanol. After fermentation process, solid-phase is still obtained in fermentation broth. This solid contains yeast extract that has an antioxidant compound, called glutathione. Glutathione can reduce oxidative stress and is widely used in pharmacies and cosmetics as an antioxidant agent. Therefore, this study aims to obtain antioxidant compounds by solid-phase extraction in bioethanol fermentation broth. The variation of substrate amount (10% and 15% w/v of EFB) and yeast amount (1% and 2% w/v) was used in bioethanol production through separate hydrolysis and fermentation (SHF) methods. After fermentation, the solid phase was separated from liquid phase using centrifugation process. Then, the antioxidant compound was extracted by maceration and sonication using 100% methanol. Antioxidant activity of glutathione was tested with DPPH method using Spectrophotometer UV-Vis. The results showed that the highest ethanol content was 49.94 g/L from a variation of 1% yeast and 15% pretreated EFB and the antioxidant activity (IC¬50) was 203.08 mg/L from 1% yeast and 10% pretreated EFB. The results indicated that antioxidants can be obtained as co-product in bioethanol production, thus, it could provide added value to the biorefinery of lignocellulosic bioethanol.