Energy sources of non-starter lactic acid bacteria isolated from Cheddar cheese

Abstract

Abstract The range of carbon sources available in cheese curd during maturation that could be used as energy and growth substrates by 60 cultures of non-starter lactic acid bacteria isolated from Cheddar cheese was determined by the detection of tetrazolium salt reduction in Biolog MT1 microplates ™ . There were marked inter-species and strain differences in the range of carbon substrates catabolized by the 11 Lactobacillus spp. and 2 Weissella spp. examined. Sugars were used widely among the NSLAB with 90, 100 and 85% of the isolates metabolizing lactose, glucose and galactose, respectively. In addition, ribose, N -acetyl-galactosamine and sialic acid, potentially derived from nucleic acid and casein deglycosylation, were catabolized by 58, 48 and 22% of the isolates, respectively. Lactic acid was also a potential substrate for 15% of the isolates but Tween 80 was not an effective substrate. Although 50% of the NSLAB removed citric acid from the growth medium it was not an independent energy source. Peptides and amino acids were also catabolized by up to 27% of the NSLAB provided that an exogenous source of α -ketoglutaric acid was present to facilitate the aminotransferase-mediated transamination degradative pathway. The MT1 microplate method facilitates the rapid screening for isolates able to establish in the cheese curd and for the detection of specific metabolic activities in isolates undergoing evaluation for use as adjunct cultures in cheesemaking trials.