|DIEZ GONZALEZ, FRANCISCO|
Submitted to: Archives of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/1996
Publication Date: N/A
Interpretive Summary: Acid whey from cheese making is major source of environmental pollution that has not been easy to remedy. The material is too dilute to ship, too acidic to use as an animal feed and not valuable enough to dehydrate. One possible mechanism of disposal could be bioconversion. We have identified a bacterium, Clostridium acetobutylicum, that is able to utilize elactate from acid whey. This paper describes the enzymatic regulation of C acetobutylicum. Lactate utilization by C. acetobutylicum may provide a means of converting acid whey into industrial solvents.
Technical Abstract: Clostridium acetobutylicum strain P262 could use either glucose, pyruvate or lactate and acetate as an energy source for growth. All of these substrates were converted to acetate or butyrate, but the ratio of acetate to butyrate varied from 0 to 8. Butyrate producing enzymes (butyryl-CoA dehydrogenase and butyrate kinase) could explain the fermentation changes, but acetate kinase activity and butyrate production were negatively correlated (R2=0.99). Butyrate formation was highly correlated with the log NADH to NAD ratio of the cells, and log NADH to NAD and acetate kinase activity of cell-free extracts were negatively correlated (r2=1.00). Based on these results, it appeared that reducing equivalents were regulating the relative flux of acetyl-CoA to acetate or butyrate. Cells of P262 produced a single acetate kinase that had a pH optimum of 8.0, a Km for acetate of 160 mM and a Vmax of 200 umol mg protein-1 min-1. The enzyme had a native molecular weight of 78 kDa, but a size of only 42 kDa on SDS PAGE indicate that the acetate kinase of P262 was probably a dimer.