Project Number: 6621-41000-011-00
Project Type: Appropriated

Start Date: Jun 16, 2004
End Date: Jun 15, 2009

Objective:
Characterize the structure and functional properties of the polysaccharides present in the citrus processing waste stream. Develop new and use existing procedures including chemical, physical or enzymatic processes to modify and produce new polysaccharide materials, value added polymers, or resins with unique functional properties. Develop new industrial uses for new products produced either isolated or while still contained in the bulk waste stream residue for use as ion-exchange, building and construction materials, paper products, and other non-food related materials. Develop economically viable method for enzymatic and chemically catalyzed depolymerization of polysaccharides in citrus waste streams to monomeric sugars with subsequent fermentation of hydrolysates to value added products such as ethanol, citric and other organic acids, and similar products.

Approach:
Reactions initiated by acid, base, enzymes, and/or thermal treatments will be performed to modify polysaccharides in bulk citrus processing waste or minimally separated citrus waste stream components. Pectinmethyesterase enzymes from citrus will be characterized for their response to temperature, pH, salt, and modifications made to pectin substrates. The effect of modifications on chemical changes such as degree of esterification, fragmentation size and polymerization will be determined along with how these modifications improve water holding capacity, increase ion-exchange capacity, decrease or increase viscosity and other rheological properties. Polysaccharides in citrus residue products and pectin extracts will also be further modified using nucleophilic reagents such as amines and sulfhydryl compounds to produce substituted polymers with new functionality. New grinding, separation and/or filtration process technologies will also be evaluated for economic and environmental advantages for production of more economically attractive carbohydrate and polysaccharide products from citrus waste streams. Products with desirable properties will be produced on a pilot scale and supplied to industrial partners for testing in specific applications. Modified polysaccharides will be tested in applications such as dry strength additives for paper and building materials, metal chelation and ion exchange applications such as industrial wastewater treatment, and water binding capacity for superabsorbant applications. Commercial enzyme systems for efficient hydrolysis of polysaccharides from citrus waste will be evaluated to optimize enzyme loading, temperature and pH of reactions, ability to recycle enzymes, and degree of mixing necessary in pilot scale-up from lab scale experiments. Efficient separation of hydrolysed citrus waste will then be investigated using centrifugation, rotary and flat bed filters to allow fermentation to produce fuel ethanol and organic acids.