Date of Award

1987

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Sciences

First Advisor

Samuel P. Meyers

Abstract

Millions of pounds of readily usable and renewable byproduct are discarded yearly from the rapidly expanding Louisiana crawfish processing industry. This investigation involved utilization of crawfish waste shell to produce the biopolymers chitin and chitosan, and to utilize chitosan as a coagulant and in ligand-exchange column technology for recovery of organic compounds from seafood processing discharge stickwater. Crawfish shell was found to be an excellent source of chitin (23.49% on a dry basis) and applicable physicochemical procedures for isolation of chitin from crawfish shell and its conversion to chitosan were developed. Particular attention was given to characterization of the physicochemical properties of crawfish waste and its chitinous biopolymers. Crawfish chitosan coagulated suspended solids in stickwater obtained from the crawfish pigment extraction process as effectively, or greater, than seven commercial polymers and four inorganic salts under the test conditions. Concentration of suspended solids and turbidity were reduced 97% and 83%, respectively, by treatment with 150 mg/L chitosan at pH 6.0, with a 45% reduction in chemical oxygen demand (COD). Proximate and amino acid analyses indicate that the coagulated solids have potential as a nutritious ingredient in livestock feed formulations. Crawfish chitosan was demonstrated to be an effective ligand-exchange column material for recovery of amino acids (principal flavor precursors in shellfish) from seafood processing wastewater. In comparison with commercial chitosan, crawfish chitosan, loaded with copper or amino copper, showed higher recovery rates of amino acids. Recovery of amino acids from the amino copper-crawfish chitosan column was pH dependent. With increasing pH, recovery of amino acids was greatly reduced. Slight elution of copper by ammonia eluent occurred at pH 9, but not at pH 10 and 11. However, the eluate was completely free of copper ions when treated with a second crawfish chitosan column. In view of the increasing need for large volume sources of raw chitinous material for chitosan production and promising commercial applications of this polymer, effective exploitation of crawfish shell waste for production of chitosan, combined with extraction of carotenoid pigment, is warranted.

Pages

203

DOI

10.31390/gradschool_disstheses.4468

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