Title page for ETD etd-53261753976940


Type of Document Dissertation
Author Nassif, Lana Amine
Author's Email Address lnassif@vt.edu
URN etd-53261753976940
Title The Production of 2-Keto-L-Gulonic Acid by Different Gluconobacter Strains
Degree Master of Science
Department Biology
Advisory Committee
Advisor Name Title
Krieg, Noel R.
McNair, Harold M.
Wolfe, James F.
Claus, G. William Committee Chair
Keywords
  • mixed culture
  • sorbose
  • 2-keto-L-gulonic acid
  • thin layer chromatography
  • Gluconobacter
  • high performance liquid chromatography
Date of Defense 1997-02-14
Availability unrestricted
Abstract
Vitamin C is industrially produced by the Reichstein

method, which uses gluconobacters to oxidize sorbitol

to sorbose then a chemical process to convert

sorbose to 2-keto-L-gulonic acid (2-KLG). The

establishment of a more extensive microbial process

for 2-KLG production translates into a less expensive

and more efficient production of vitamin C. I

examined pure strains and mixed cultures for their

ability to produce 2-KLG using thin layer and high

performance liquid chromatography. The DSM 4027

mixed culture produced the highest yield, 25 g/L, of

2-KLG from 100 g/L of sorbose, while the

gram-negative rods isolated from DSM 4027

produced 8.8 g/L, and B. megaterium isolated from

DSM 4027 produced 1.4 g/L. Thus, the

gram-negative rods in the mixed culture were the

primary 2-KLG producer, but B. megaterium in the

DSM 4027 mixture enhanced this synthesis. Authentic

pure cultures of Gluconobacter oxydans IFO strain

3293 and ATCC strain 621 produced 3.4 g/L and

5.7 g/L, respectively. Attempts to co-culture the

isolated B. megaterium with the isolated

gram-negative rods and authentic Gluconobacter

strains did not increase 2-KLG production, nor did

growing the cultures on B. megaterium spent media.

Bacillus megaterium produced an unidentified

keto-compound detected on the TLC

chromatograms, which suggested that B. megaterium

converted sorbose to an intermediate that may then be

converted by the gram-negative rods in DSM 4027 to

2-KLG. Limited phenotypic tests suggested that the

gram-negative rods in the DSM 4027 mixture are not

gluconobacters.

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