Biochemical characterization of Bacillus paramycoides DW1, a bacterial isolate from dairy waste water

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

Science Vision 25 (1), 26-33 | Published on 27 August 2025 | 10.33493/scivis.25.01.05

Abstract

Bacillus paramycoides DW1 (hereafter B. paramycoides DW1), an isolate from dairy waste water is a gram-positive, rod-shaped, endo-spore forming bacterium. The aim of this study was to assess the ability of this bacterium to hydrolyze lactose, proteins, and lipids (major organic constituents of dairy waste water), and its potential to grow using lactose, glucose, and galactose as sources of carbon, and ability to utilize other complex carbohydrates. The results suggest that lactose is a good source of carbohydrate for B. paramycoides DW1 growth. Although the best growth of the bacterium was observed in the presence of 2% lactose, it was able to grow even at higher concentration of lactose (5%) usually encountered in dairy waste water, and could also utilize a variety of other carbohydrates, such as xylose, cellobiose, saccharose, trehalose, glucose, and galactose. Concomitant with its growth using lactose, B. paramycoides DW1 displayed lactose-hydrolyzing intracellular β-D-galactosidase activity irrespective of concentrations of lactose with the highest being at 2%. This activity was inhibited in bacterial cells grown in the presence of glucose and galactose and by a metal ion chelator ethylene diamine tetraacetic acid (EDTA) suggesting that the enzymatic reaction is catabolite repressible and requires metal ions for its activity. Further biochemical characterization revealed that a neutral pH (7.0) and mesophilic temperature (37°C) was optimum for β-D-galactosidase activity in B. paramycoides DW1. Additionally, the bacterium was also endowed with extracellular protease (caseinolytic) and lipase activities. Overall, the findings reveal that the potential to hydrolyze lactose, protein, and lipid probably enables B. paramycoides DW1 to grow and survive in nutritionally complex dairy waste water environment and implies that such a bacterium may be a significant contributor to reduction of organic pollutant load in dairy waste water.

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