This study investigated the use of sweet potatoes (Ipomoea batatas ) as a basic component to develop a medium for cultivation of lactic acid bacteria (LAB). Extract from baked sweet potatoes was used to form a sweet potato medium (SPM). SPM was supplemented with 4 g/L of each nitrogen source (beef extract, yeast extract, and proteose peptone #3). Lactobacilli MRS was used as a control medium. Ten LAB strains were used to determine the suitability of SPM serving the growth of LAB. Our results showed no significant (p < 0.05) differences in the optical density, maximum specific growth rates, and bacterial populations between MRS and SPM. SPM also maintained higher pH values throughout the incubation period compared to that in MRS. The cost of SPM was 47% less than the cost of MRS. Further step was taken to determine the suitability of SPM serving LAB enzymatic activity. LAB strains growing in SPM showed relatively higher β-glucosidases, acid phosphatase, and phytase activities and lower &agr;-glucosidase compared to that in MRS. Strains of L. reuteri showed the highest enzymatic activities of &agr;-glucosidase, acid phosphatase, and phytase whereas L. delbrueckii subsp. bulgaricus showed the highest β-glucosidases activity. Thus the enzymatic activity of L. reuteri growing in SPM was enhanced using six different metal ions. The response of L. reuteri strains to metal ions found to be strain dependent. The addition of Mg2+ and Mn2+ followed by the addition of Ca2+ showed the highest enhancement effect on all tested enzymes. These findings indicated that SPM is a suitable medium serving the growth and bioactivities of LAB and thus could be used as an alternative low cost medium.
|Advisor:||Ibrahim, Salam A.|
|Commitee:||Schimmel, Keith, Shahbazi, Abolghasim, Song, Danfeng, Walker, Jane, Worku, Mulumebet|
|School:||North Carolina Agricultural and Technical State University|
|Department:||Energy and Environmental Systems|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 75/01(E), Dissertation Abstracts International|
|Subjects:||Food Science, Microbiology|
|Keywords:||Bacterial population, Enzymatic activity, Growth rate, Lactic acid bacteria, Metal ions, Sweet potato medium|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be