Degree Type

Dissertation

Date of Award

1991

Degree Name

Doctor of Philosophy

Department

Food Science and Human Nutrition

First Advisor

Bonita A. Glatz

Abstract

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.

DOI

https://doi.org/10.31274/rtd-180813-9357

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Steven A. Woskow

Language

en

Proquest ID

AAI9212204

File Format

application/pdf

File Size

151 pages

Included in

Microbiology Commons

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