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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Research » Publications at this Location » Publication #35638
Title: THE ROLE OF AN NAD-INDEPENDENT LACTATE DEHYDROGENASE AND ACETATE IN THE UTILIZATION OF LACTATE BY CLOSTRIDIUM ACETOBUTYLICUM P262

Author
item DIEZ-GONZALEZ FR - CORNELL UNIVERSITY
item Russell, James
item HUNTER JANE B - CORNELL UNIVERSITY

Submitted to: Archives of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Acid whey from cheese making is a major source of environmental pollution that has not been easy to remedy. The material is too dilute to ship, too acidic to be used as an animal feed, and not valuable enough to dehydrate. One possible mechanism of disposal would be bioconversion. We have identified a strain of Clostridium acetobutylicum that is able to utilize the lactic acid from acid whey. This bacterium has a very high rate of lactic acid metabolism, but it needs acetic acid as a cofactor. Our research demonstrated that the acetic acid was serving as an electron acceptor. If hydrogen production could be used an alternative electron sink, C. acetobutylicum should be able to utilize only lactic acid. C. acetobutylicum currently converts lactic acid to butyric acid, but it is also able to produce butanol, a valuable solvent. If we can get C. acetobutylicum to convert all of the lactic acid to butanol, cheese making plants could have an inexpensive method for disposing of acid whey.

Technical Abstract: Clostridium acetobutylicum P262 could use lactate as an energy source for growth with acetate as co-substrate. Lactate was utilized at a rapid rate (600 nmol/mg protein-min) and the growth rate was 0.05 h-1. Butyrate, carbon dioxide and hydrogen were the end-products of lactate and acetate utilization, and the stoichiometry was 1 lactate +0.4 acetate ---> 0.7 butyrate + 0.6 H2 + 1CO2. Lactate-grown cells had 2-fold lower hydrogenase than glucose-grown cells and the lactate-grown cells used acetate as an alternative electron acceptor. The cells had a poor affinity for lactate (Ks = 1.1mM), and there was no evidence for active transport. Lactate utilization was catabolized by an inducible NAD- independent lactate dehydrogenase (iLDH) that had a pH optimum of 7.5. The iLDH was 5-fold more active with D-lactate than L-lactate, and the Km for D-lactate was 3.2 mM. Lactate-grown cells had little butyraldehyde dehydrogenase activity, and this defect did not allow the conversion of lactate to butanol.