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.