Enteric Bacteria and Biodiesel Byproduct in Undergraduate Research

Graves, James., Tone. Shamon, and Vincent. Vuljaj

Escherichia coli and Klebsiella species have become

important in biofuel research because strains have

been engineered that produce ethanol, butanol or

microdiesel. These bacteria which naturally utilize pure

glycerol were assessed for potential to utilize biodiesel

glycerol byproduct made by transesterification or

catalyst column. To determine if byproduct contained

inhibitory components E. coli was cultured in nutrient

broth to which byproduct had been added. Culture

optical density (OD) was measured by use of a Klett –

Summerson colorimeter. Growth in culture containing

byproduct from transesterification was slightly

decreased while that in culture containing byproduct

from catalyst column was increased. Bacteria were

grown in minimal broth to evaluate byproduct as an

individual carbon source. Byproduct made by

transesterification was pH adjusted due to high

alkalinity. There was not a considerable difference

between culture ODs produced from glycerol and

byproduct from catalyst column. Byproduct from

transesterification did not support growth as well

as that from catalyst column. K. pneumoniae appeared

to utilize glycerol and byproduct better than E. coli. Both

organisms grew significantly better on glucose than

glycerol. A rapid solid phase glucose oxidase and

peroxidase based assay (Precision Labs, Inc.) was

used to detect glucose in cultures. Both E. coli and K.

pneumoniae lowered added glucose to an

undetectable level. A rapid solid phase alcohol oxidase

and peroxidase based assay (AlcoScreen) was used

to detect alcohol. E. coli showed a positive test for the

presence of alcohol in cultures produced from glucose

or glycerol. It was unknown if alcohol was made from

byproduct because stock solutions showed a positive

test for the presence of alcohol. These observations

indicate that enteric bacteria may be able to utilize

biodiesel glycerol byproduct as an industrial feedstock.