Evaluation of growth and hydrolytic enzyme activities in Enterococcus faecium PB1, a probiotic bacterium with potential for application in dairy waste water treatment

Jugami Boro, Mintu Medhi, Asahan Ali, Tovikali Zhimo, Jyotirmoy Bhattacharya

Science Vision 25 (1), 10-18 | Published on 27 August 2025 | 10.33493/scivis.25.01.03

Abstract

Enterococcus faecium PB1 is a gram-positive, round-shaped, commercially important (probiotic) lactic acid bacterium. The present study was aimed to evaluate the ability of this bacterium to utilize the complex disaccharide lactose as a source of carbon for growth, and its enzymatic potential to hydrolyze lactose, proteins, and lipids. The results revealed that E. faecium PB1 can grow in the presence of a range of lactose concentrations (1-5%) with optimum growth at 2%. As with lactose, the bacterium was able to grow well in the presence of simple sugars glucose and galactose and, utilize various other carbohydrates. E. faecium PB1 exhibited β-D-galactosidase activity (an intracellular lactose-hydrolyzing enzyme) at all the concentrations of lactose tested; the maximum being observed at 2%. A neutral to moderate alkaline pH range (7.0-8.5) and mesophilic temperature (37°C) was optimum for β-D-galactosidase activity in E. faecium PB1. Ethylene diamine tetraacetic acid (EDTA, a metal ion chelator), glucose and galactose (the breakdown products of lactose) inhibited this activity. E. faecium PB1 also displayed extracellular protein-degrading protease activity in cells grown with lactose and galactose. Although no extracellular lipid-degrading lipase activity could be detected in cells grown with lactose, this activity was present in cells grown with glucose and galactose. Taken together, the ability of the probiotic bacterium E. faecium PB1 to grow at a range of lactose concentrations and its potential to hydrolyze lactose, proteins, and lipids may be suitably exploited for biological treatment of dairy waste waters rich in similar types of organic nutrients.

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