Production of ethanol and feed by high dry matter hydrolysis and fermentation of palm kernel press cake.
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, beta-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.
Forest and Landscape Denmark, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg, Denmark. hnj@life.ku.dk
Henning
H
Jørgensen
Anand R
AR
Sanadi
Claus
C
Felby
Niels Erik Krebs
NE
Lange
Morten
M
Fischer
Steffen
S
Ernst
D056804:Biofuels; D044602:Cellulases / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006868:Hydrolysis; D008358:Mannose / Q000378:metabolism; D000073878:Palm Oil; D010938:Plant Oils / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D044902:beta-Mannosidase / Q000378:metabolism
D056804:Biofuels; D010938:Plant Oils; D029701:Saccharomyces cerevisiae Proteins; D000431:Ethanol; D000073878:Palm Oil; D044602:Cellulases; D044902:beta-Mannosidase; D005947:Glucose; D008358:Mannose