DETAILED DESCRIPTION OF THE INVENTION Waste materials containing cellulose which have previously been disclosed as potential sources for degradation to simple organic molecules with the concurrent manufacture of a protein useful in animal feed are also useful as adsorbants for an enzyme recycling process.
Sources of this waste material include municipal waste, paper mill waste, saw mill waste, cotton gin waste, and the like.
Of particular utility are waste paper and cardboard which can be pre-swelled or pulped and will form a loosely packed plug useful for filtration or for slurry adsorption and which contains sufficient surface sites for enzyme adsorption.
Alternatively, a purified cellulose product can be used as an adsorbent which is then added to the starting materials.
Such a purified cellulose is sold by American Viscose Division, FMC Corporation, Newark, Del.
, under the trade name Avicel.
Upon completion of a simultaneous saccharification-fermentation reaction, that is, upon reaction to substantial equilibrium, the reaction medium contains unreacted cellulose, solid oligosaccharides, lignocellulosic materials, and other undefined solid degradation products as well as alcohol, nutrients, cellulase enzyme components, and yeasts and yeast cells.
Filtration to remove the solid materials is usually the first step in purification of the desired ethanol product.
The filtrate is then subjected to a vacuum stripping operation to remove the ethanol.
By the method of this invention the enzymes from the saccharification reaction are saved and recycled prior to ethanol stripping.
By the method of this invention, any cellulose-containing solid material with sufficient surface area to provide binding sites for the enzyme, is contacted with the enzyme-containing filtrate from a simultaneous saccharification-fermentation reaction which has been allowed to attain substantial equilibrium of reaction.
The method of contacting can be by adding the cellulose solid to form a slurry and rapid filtration of the slurry to recover the enzyme-cellulose solid or by passing the enzyme-containing filtrate through a plug of loosely packed cellulose solid
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Molecular Biology 
