Proteolytic and other hydrolytic enzyme activities in non-starter lactic acid bacteria (NSLAB) isolated from cheddar cheese manufactured in the United Kingdom

Abstract

The populations of non-starter lactic acid bacteria (NSLAB) in a selection of 15 good-quality UK-manufactured Cheddar cheeses that had been matured for 6–9 months ranged from 105 to 107 bacteria g-1. Fifteen different species of lactic acid bacteria were identified using commercially-available identification systems. The species isolated most frequently were Lactobacillus paracasei subsp. paracasei and Lb. plantarum; 10 other species were isolated from two or more cheeses and three species were recovered from only a single cheese. There were marked differences in the NSLAB populations of the cheeses produced by different UK manufacturers, and differences were also apparent in the populations of two cheeses produced on different occasions at the same creamery. Forty-one isolates, selected to include all the species identified and the dominant strains present in cheeses produced at several different creameries, were screened for activities of 34 proteolytic, five glycoside hydrolase and five esterolytic enzymes. All the NSLAB possessed a wide range of hydrolytic enzymes and therefore had the potential to contribute at some stage to the development of cheese flavour during the maturation and ripening period. Inter-species and strain differences in enzyme profiles and levels of activity were apparent and were determinants for the non-random selection of NSLAB for use as adjunct cultures in subsequent cheese-making trials. The breakdown of diagnostic substrates was indicative of the presence of multiple proteinase, tripeptidase, dipeptidase (including prolinase-and prolidase-like), dipeptidyl peptidase, prolyl, proline, aspartyl, pyroglutamyl (pyrrolidonecarboxyl) and general aminopeptidase activities.