Date of Award
Doctor of Philosophy
Food Science and Human Nutrition
Bonita A. Glatz
A method for semi-continuous fermentation using a propionic acid tolerant mutant of Propionibacterium acidipropionici was developed that increased the yield of propionic acid. This strain was able to grow in medium containing up to 8% propionic acid. Propionic acid yields of approximately 5% were obtained within 5 days of fermentation in a semi-continuous process. Uncoupling of growth and acid production occurred during fermentation with the mutant strain, carbohydrate continued to be metabolized though growth and acid production had ceased;A new method for more efficient production of protoplasts was developed. By growing strain P104 in sodium lactate broth supplemented with 1% threonine and treating these cells with a combination of lysozyme and protease enzymes, osmotically sensitive cells were produced able to regenerate on hypertonic medium to walled cells;Attempts to transfer transposons and plasmid DNA into propionibacteria by polyethylene glycol-induced protoplast transformation, electroporation, and conjugation were made. Antibiotic-resistant cells often appeared during these experiments, but autonomous plasmid DNA was never isolated in recipients. However, DNA hybridization of putative protoplast transformants indicated possible chromosomal integration of the plasmids.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Steven A. Woskow
Woskow, Steven A., "Improved production of propionic acid by strains of Propionibacterium " (1991). Retrospective Theses and Dissertations. 9788.