ARS | Publication request: LACTOBACILLUS CASEI METABOLIC POTENTIAL TO UTILIZE CITRATE AS AN ENERGY SOURCE IN RIPENING CHEESE: A BIOINFORMATICS APPROACH

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 2006
Publication Date: N/A

Interpretive Summary: Selected strains of lactic acid producing bacteria are present in cheese as the result of contamination. Despite multiple efforts to identify the contamination route for selected lactic acid producing bacteria in cheese, it is still unknown. Growth of these bacteria in cheese influences cheese flavor development. Therefore, it is important to control their growth in cheese. Citric acid is an energy source for growth of lactic acid producing bacteria in cheese. Utilization of citric acid as an energy source means that this molecule is converted into smaller molecules refer to as end-products. This research revealed that end-products of citric acid utilization by a lactic acid producing bacterium include flavor compounds, and flavor compound precursors such as diacetyl, acetoin, and butanediol. Other end-products of citric acid utilization identified are formic acid, ethanol, acetic acid, and off course lactic acid. Diacetyl is the source for butter-like flavor, and a precursor of other flavor compounds. Acetic acid is commonly used in the food industry for the acidification of foods. Lactic acid is the source of the characteristic flavor in cheese. Additionally, this research identified potential metabolic routes for the conversion of citric acid into all the end-products mentioned above. The results obtained in this study will help researchers in the design of strategies for better controlling growth of these lactic acid producing bacteria or contaminants in cheese, and to better control and/or enhance cheese flavor development.

Technical Abstract: This research describes a unique PCAC for Lactobacillus casei. Additionally, it describes the citric acid catabolism end-product by this non-starter lactic acid bacteria during growth, and under conditions similar to those present in ripening cheese. It provides insights on pathways preferably utilized to derive energy in the presence of limiting carbohydrates by this microorganism.