2016 Volume 95 Issue 7 Pages 599-604
Chlorella is single-cell green algae which has the photosynthetic pigments chlorophylls. Through photosynthesis, it multiplies rapidly, requiring only carbon dioxide, water, sunlight, and a small amount of minerals. Since dried chlorella is composed of about 45% protein, 20% fat, 20% carbohydrate, and others, ethanol yield is low through saccharification and fermentation of chlorella. Therefore, hydrogen production from chlorella was examined through enzymatic hydrolysis and photocatalytic reaction over a Pt-loaded TiO2 photocatalyst (Pt/TiO2). Enzymatic hydrolysis of chlorella (10.0 g) was performed in phosphate buffer (60 mL) using hydrolytic enzyme (1.0 g) such as protease, cellulase, and xylanase. After hydrolysis, the precipitates were removed by centrifugation to give the supernatant aqueous enzymatic hydrolyzed solution (EH). It was found that the EH solution obtained from protease-hydrolysis contained large amounts of hydrolyzed materials as a consequence of freeze-drying. Main component in EH solution was found to be amino acids by colorimetric analysis using ninhydrin The EH solution was subjected to the sacrificial hydrogen production over a Pt/TiO2 under UV irradiation by a high-pressure Hg lamp. Hydrogen (57.9 mg) was obtained from 1.0 g of dried chlorella through protease-hydrolysis and photocatalytic hydrogen production over Pt/TiO2. This is the first report on sacrificial H2 production from chlorella.