Co-production of fumaric acid and chitin using Rhizopus oryzae fermentation on a nitrogen-rich agricultural residue: Dairy manure

Animal manure treatment remains a significant challenge to the United States livestock industries. As the traditional animal manure management practice of land application faces increasing environmental and regulatory scrutiny, the concept of using animal manure as a biomass for producing value-added products offers a potential alternative. Animal manure contains a variety of components including fiber, proteins/amino acids, and minerals. Such components are ideal feedstocks for producing value-added products by either biological or chemical conversion processes. The aim of this research was to develop a new process for the utilization of both nitrogen and carbohydrate sources in dairy manure to simultaneously produce two valuable chemicals: fumaric acid and chitin. The research included: (1) liquid/solid separation to obtain a nitrogen-rich manure liquid stream and carbohydrate-rich manure fiber stream, and their characterization; (2) investigation of effects of various hydrolysis methods including acid hydrolysis and enzymatic hydrolysis on manure fiber; (3) modeling enzymatic hydrolysis kinetics of differently treated manure fiber; (4) investigation of pellet formation for the fungal strain--- Rhizopus oryzae; and (5) co-production of fumaric acid and chitin from pre-treated dairy manure using a pelletized filamentous fungus--- Rhizopus oryzae.; Several major conclusions have been obtained from the research: (1) nitrogen in dairy manure had a significant impact on the conversion of manure fiber into monosaccharides so that separation of the nitrogen-rich liquid stream must be carried out before the conversion process takes place; (2) enzymatic hydrolysis with dilute alkaline peroxide treatment was suggested to be the better pre-treatment method to complete the conversion of fiber to monosaccharides in terms of both technical and environmental concerns; (3) pelletized fungal biomass of the fumaric acid producing strain---R. oryzae 20344 was achieved using a simple and new culture method; (4) when compared to other nitrogen sources, manure liquid was shown to be a better nitrogen source for chitin accumulation during the fungal biomass cultivation step; and (5) a three-step fermentation process: pellet seed culture, biomass cultivation on liquid manure to produce the biomass and chitin, and fumaric acid production on the hydrolysate from manure fiber was found to be the optimal process to simultaneously produce the target chemicals of chitin and fumaric acid.