(421bh) Front-End Recovery of Protein From Wet Biomass and Effect On Pretreatments of Partially Deproteinized Fiber

Protein is one of the major components in biomass, after cellulose, hemicellulose, and lignins. Depending on type of biomass source, protein content varies from as low as 3.3% w/w in dry corn stover to 13 to 15% w/w in mature alfalfa hay. The current biomass-to-bioenergy models are based on dry biomass as feedstock and make no effort of recovering the protein, either from front-end or the tail-end of the pre-treatment/fermentation processes. High quality protein for food or feed utilization, along with pigment xanthophylls, which are sought after in poultry feed, could be removed from green or wet biomass prior to processing for bioenergy/biochemicals. Potentially less severe pretreatment might be required for partially deproteinized fiber for downstream processing via biochemical route.

The early-fall alfalfa and switchgrass, at about 80% moisture content, were macerated in blender with either aqueous potassium hydroxide (KOH), aqueous sodium dodecyl sulfate (SDS), or water to extract the juice. The partially deproteinized fiber and control biomass samples were pretreated by two different pretreatment methods; (1) dilute sulfuric acid (DSA) and (2) ammonia recycle percolation (ARP).

In this study, we report findings of front-end protein recovery and pretreatment of partially deproteinized alfalfa and switchgrass fiber. Preliminary results indicated that both the caustic and SDS treatments were effective in removing more than 50% of initial biomass protein from alfalfa and switchgrass biomass. Enzymatic digestibility test results also indicated that ARP is more effective method for both deproteinized fibers than DSA. In summary, protein was recovered from wet biomass prior to pretreatment and enzymatic digestibility tests. Addition of chemicals, e.g, KOH and SDS in extraction media significantly improved the protein recovery compared to water alone. Enzyme digestibility tests showed that deproteinization of biomass makes fibers more accessible to hydrolytic enzymes.