Factors affecting use of sorbitol as a carbon source by exponentially growing Gluconobacter oxydans ATCC 19357

Gluconobacters are known for their rapid oxidation of large quantities of sorbitol (SL) and quantitative conversion to sorbose (SE). Whether SL is assimilated into cell material has not been examined before and was investigated in this study. The effect of changing growth and oxidation rates on use of SL as a carbon source was also examined. Cells were first grown in Standard Medium containing 5% SL, 1% peptone (PE), 1% yeast extract (YE) and 20 µCi/flask of U-¹⁴C-SL. Cells were harvested, washed and fractioned with cold trichloroacetic acid (TCA) to separate the soluble low molecular weight metabolites (TCAs) and the insoluble polymers (TCAi). After 6 h (5 generations) of exponential growth at a rate of 0.094 mg dry cell weight (DCW)/ml/hr and an oxidation rate of 4.91 mg 51/ml/hr, 97% of the radioactivity remained in the growth medium as SL or SE. The TCAi fraction from these cells contained 0.4 mg SL equivalents (eq)/mg DCW and the TCAs fraction contained 0.24 mg SL eq/mg DCW (avg). Removing PE and reducing YE concentration from the Standard Medium decreased growth rate to 0.031 mg DCW/ ml-hr and oxidation rate to 2.79 mg SL/ml-hr. The TCAi fraction contained 0.09 mg SL eq/mg DCW and the TCAs fraction contained 0.266 mg SL eq/mg DCW. Reducing the sorbitol concentration of the Standard Medium from 5% to 1% decreased the growth rate to 0.066 mg DCW/ml-hr and the oxidation rate to 1.92 mg SL/ml-hr. The TCAi fraction contained 0.025 mg SL eq/ mg DCW and 0.079 mg SL eq/mg DCW was present in the TCAs fraction. The amount of SL incorporated was not directly coupled to growth rate, oxidation rate or metabolite pool size. SL is used as a carbon source during growth, and accounts for as much as 40% of the dry cell mass.

Name thesis:degree_name

M.S.

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Microbiology

Department dc:contributor.department

Microbiology

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1983

Author dc:creator

• Feshami, Barbara H.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10919/118340

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/118340