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Biotechnology and Applied Biochemistry (2002) 36, (1–6) (Printed in Great Britain)

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Production and characterization of a thermostable b-galactosidase from Bacillus coagulans RCS3

Navneet Batra*, Jagtar Singh*, Uttam C. Banerjee†, Pratap R. Patnaik‡ and Ranbir C. Sobti*¹

*Department of Biotechnology, Panjab University, Chandigarh, India, †Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Mohali, India, and ‡Institute of Microbial Technology, Sector 39-A, Chandigarh, India

Key words: lactose hydrolysis, inhibition, thermostability.

Abbreviations used: ONP, o-nitrophenol; ONPG, o-nitrophenyl b-D- galactopyranoside.

¹To whom correspondence should be sent (e-mail rcsobti@panjabuniv.chd.nic.in).

A strain of Bacillus coagulans RCS3 isolated from ahot-water spring produced significant b-galactosidase activity at 10 days of growth in a flask. While enzyme production was maximum at 50 °C, the highest activity was at 65 °C, where the half-life was 2 h. A 2 °C decrease in temperature increased the half-life to 15 h without significantly changing the activity, suggesting that 63 °C is the temperature of preference compared with 65 °C for a combination of good activity and stability. The b-galactosidase was also stable over pH 5–8, with peak activity at pH 6–7. It was strongly and competitively inhibited by the hydrolysis product galactose. Bivalent cations (Cu²⁺, Ni²⁺ and Hg²⁺) in the concentration range of 0.5–2.0 mM also inhibited enzyme activity. Both lactose solution and whey could be hydrolysed substantially within 36 h at 50 °C. The thermostability and pH-stability and good hydrolytic capability make this enzyme potentially useful in the dairy industry.

Received 8 November 2001/25 February 2002; accepted 11 March 2002

Portland Press Ltd © 2002