Production of Ethanol and Feed by High Dry Matter Hydrolysis and Fermentation of Palm Kernel Press Cake

• Published in: Applied biochemistry and biotechnology 2010-05, Vol.161 (1-8), p.318-332
• Main Authors: Jørgensen, Henning, Sanadi, Anand R, Felby, Claus, Lange, Niels Erik Krebs, Fischer, Morten, Ernst, Steffen
• Format: Article
• Language: English
• Subjects: beta-mannosidase; beta-Mannosidase - metabolism; Biochemistry; Biofuels; Biological and medical sciences; Biorefineries; Biotechnology; cellulases; Cellulases - metabolism; Chemistry; Chemistry and Materials Science; Dry matter; dry matter content; enzymatic hydrolysis; Ethanol; Ethanol - metabolism; ethanol production; feed processing; Feed supplements; feeds; Fermentation; Fundamental and applied biological sciences. Psychology; Glucose - metabolism; hexoses; hydrolysates; Hydrolysis; Mannose - metabolism; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; palm kernel oil; Palm Oil; palm oils; Plant Oils - chemistry; Proteins; saccharification; Saccharomyces cerevisiae; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - metabolism; Sugar; Yeast; yields
• ISSN: 0273-2289; 1559-0291
• DOI: 10.1007/s12010-009-8814-6

Palm kernel press cake (PKC) is a residue from palm oil extraction presently only used as a low protein feed supplement. PKC contains 50% fermentable hexose sugars present in the form of glucan and mainly galactomannan. This makes PKC an interesting feedstock for processing into bioethanol or in other biorefinery processes. Using a combination of mannanase, β-mannosidase, and cellulases, it was possible without any pretreatment to hydrolyze PKC at solid concentrations of 35% dry matter with mannose yields up to 88% of theoretical. Fermentation was tested using Saccharomyces cerevisiae in both a separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) setup. The hydrolysates could readily be fermented without addition of nutrients and with average fermentation yields of 0.43 ± 0.02 g/g based on consumed mannose and glucose. Employing SSF, final ethanol concentrations of 70 g/kg was achieved in 216 h, corresponding to an ethanol yield of 70% of theoretical or 200 g ethanol/kg PKC. Testing various enzyme mixtures revealed that including cellulases in combination with mannanases significantly improved ethanol yields. Processing PKC to ethanol resulted in a solid residue enriched in protein from 17% to 28%, a 70% increase, thereby potentially making a high-protein containing feed supplement.