Coproduction of Peptic Fragments and Biofuels from Citrus Processing Waste

Pectin is, after cellulose, the second most abundant polymer on earth; but its level of utilization in industrial products is very low. High molecular weight pectin is used in food products where it suffers from stagnant markets and high production costs due to the use of organic solvents, low concentration of extracted pectin and generation of soluble sugar streams which burden the waste treatment systems. The proposed project will investigate coproduction of fragmented pectin molecules from citrus processing waste (CPW) in an integrated system with the production of limonene and fuel grade ethanol. The Citrus industry in Florida produces annually about 750,000 dry tons of CPW so there is ample low cost feedstock for both biofuel and pectic fragment production. Both products can be made from other pectin rich feedstocks. Ethanol production by simultaneous saccharification and fermentation converts neutral sugars from CPW into biofuel; decreases waste treatment problems; and provides revenues, which help offset expenses related to the overall process. Limonene contained in the extracted citrus peel oil is a valuable commodity that has to be removed prior to any anaerobic fermentation, because it inhibits or kills microorganisms. The phase I R&D effort will concentrate on stripping the limonene with steam at elevated temperatures because this approach is efficient, environmentally benign, and solubilizes pectin and hemicelluloses in the form of fragments. The fragmented pectins are soluble in water and have numerous potential uses in industry. However, the formation, extraction and recovery of these fragments need to be optimized; fragments have to be characterized; and the development of industrial products needs to be initiated. The single stage and countercurrent extraction of pectic fragments with water at different pH values will be investigated. The fragments will be recovered by precipitation and analyzed by chromatographic, enzymatic and other appropriate analytical techniques. Other components in pectic extracts will be determined as well. The development of ethanol production and recovery of limonene from CPW has been investigated for the past several years, scaled up to a large pilot plant level, and will not be a focus of the proposed project. The preliminary economic evaluation of the production of pectic fragments will be prepared and the integration of pectic fragment production with the production of ethanol from CPW will be assessed. Modification of the pectic fragments by chemical and enzymatic treatments and the development of new products from pectic fragments will be initiated later in the Phase I. The production of pectic fragments from CPW and other pectin rich feedstocks and the conversion of these fragments for industrial product application will enhance revenues and competitiveness of the domestic citrus and other industries. The R&D effort will also support increased economic opportunities in rural areas and help protect the natural resource base and the environment since it addresses conversion of wastes from the processing of existing crops in an environmentally friendly manner.