HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Vakil, J. R. Articles by Shahani, K. M. Search for Related Content PubMed PubMed Citation Articles by Vakil, J. R. Articles by Shahani, K. M.

Carbohydrate Metabolism of Lactic Acid Cultures. V. Lactobionate and Gluconate Metabolism of Streptococcus lactis UN¹

Deparment of Food Science and Technology, University of Nebraska, Lincoln 68503

ABSTRACT

Using lactose-1-¹⁴C, evidence is presented indicating that the formation of lactobionate constituted an initial intermediate in the lactose metabolism of Streptococcus lactis UN. The lactobionate thus formed seemed to be further hydrolyzed to gluconate and galactose via the enzyme lactobionase (ß-galactosidase) and then metabolized. During the lactobionate and glucose fermentations, the organism produced varying amounts of lactic, formic, and acetic acids, carbon dioxide, ethanol and glycerol, and their concentrations were comparable to those produced during the lactose fermentation. These observations and the fact that it possessed the enzyme systems of the Embden Meyerhof and hexose-monophoshate shunt pathways confirmed that S. lactis is a facultative homofermenter.

Penicillin, streptomycin, aureomycin, and terramycin inhibited mildly the lactobionase activity of S. lactis as well as the production of the enzyme by the organism. Penicillin and streptomycin inhibited almost completely the growth of the organism, the utilization of lactobionate and gluconate, and the production of various metabolites for the initial 18 to 24 hr. However, upon extended incubation up to 48 hr, the organism grew, metabolized carbohydrate substrates, and produced various metabolites at a reduced rate. In general, both penicillin and streptomycin inhibited the fermentation of lactobionate more than that of gluconate.

¹ Supported in part by a grant from the U.S. Public Health Service (National Institutes of Health), E-2486. Published with the approval of the Director as paper no. 2577, Journal Series, Nebraska Agricultural Experiment Station, Lincoln.