Presenter: Kate Sorensen, College of Science, Microbiology
Authors: Kate Sorensen, Craig Oberg, Matthew Domek, Michele Culumber, Taylor Oberg, and Donald McMahon
Faculty Advisors: Craig Oberg, College of Science, Biology; Michele Culumber, College of Science, Microbiology
Institution: Weber State University
Paucilactobacillus wasatchensis, a nonstarter lactic acid bacteria, can cause late gas production, and splits and cracks in aging cheese when it metabolizes 6-carbon sugars in cheese, particularly galactose, to a 5-carbon sugar, resulting in the release of CO2. Previous studies have not explained late gas production in aging cheese when no galactose is present. Based on the genome sequence of Plb. wasatchensis WDC04, genes for potential metabolic pathways were mapped using Knowledgebase Predictive Biology software. This metabolic modeling predicted Plb. wasatchensis WDC04 could use gluconate. Gluconate contains 6 carbons and Plb. wasatchensis WDC04 contains genes to convert it to ribose-5-P using phosphogluconate dehydrogenase by a decarboxylating step, producing CO2 during its metabolism. The goal of this study was to determine if sodium gluconate, often added to cheese to reduce calcium lactate crystal formation, could be metabolized by Plb. wasatchensis WDC04 resulting in gas production. Carbohydrate restricted MRS (CR-MRS) was mixed with varying ratios of ribose, sodium gluconate or D-galactose (total sugar content of 1%). Oxyrase® (1.8% v/v) was also used to create an aging cheese environment in selected tubes. Tubes were inoculated with a 4 d culture of Plb. wasatchensis WDCO4 and results recorded over 8 d. When inoculated into CR-MRS containing only sodium gluconate, Plb. wasatchensis WDC04 grew, confirming gluconate utilization. Of the ten ratios used, Plb. wasatchensis WDC04 produced gas in six with the most gas production resulting from the ratio of 100% sodium gluconate with no added ribose or galactose. Results showed that Plb. wasatchensis WDC04 can utilize sodium gluconate to produce CO2 gas, which could cause late gas formation in aging cheese. The presence of sodium gluconate in cheese thus becomes another risk factor for unwanted gas production, and formation of splits and cracks.