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Preliminary Evaluation of Anaerobic Production of Aminolevulinic Acid by Methanogens and Acetogens

Katherine A. Taconi and Yance L. Syarif. University of Alabama in Huntsville, 130 Engineering Building, Huntsville, AL 35899

Aminolevulinic acid (ALA) is an intermediate chemical generated and utilized for the biosynthesis of other compounds such as vitamin B12 and chlorophyll in animals, plants, algae, and bacteria. The unique properties of ALA allow it to be used as an effective, non-toxic, and biodegradable herbicide and insecticide as well as for the diagnosis and treatment of several different types of cancer. Anaerobic production of ALA using methanogens and acetogens is an attractive option for ALA production, as the substrates favored by these organisms are the primary components of many common industrial, municipal, and agricultural wastewater streams commonly treated using anaerobic digestion. Unfortunately, pure cultures of methanogens and acetogens have not been shown to produce sufficient amounts of ALA when compared to processes using other microorganisms.

The goal of this research is to evaluate ALA production by a mixed culture of acetogens and methanogens based on the hypothesis that together these two types of anaerobes can produce more ALA than either could generate alone. Preliminary work focuses on two important factors for facilitating ALA production: the type of organism used and the presence of an inhibitor that prevents degradation of the ALA. Experiments utilize different combinations of substrates, including glucose, acetic acid, and methanol, to promote and quantify ALA production by methanogens and acetogens, both individually and in a mixed culture. Experiments also evaluate the effect of several inhibitors known to improve either methanogenic or acetogenic ALA production, including levulinic acid, dioxoheptanoic acid (DOH), and oxoglutaric acid. Results will be evaluated to determine the concentration of inhibitor and substrate composition that shows the most promise for generating higher yields of ALA and to determine whether this process merits further investigation and optimization as a feasible alternative for ALA production.