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Production and characterization of a milk-clotting enzyme from Aspergillus oryzae MTCC 5341

Kurutahalli, S. Vishwanatha and Appu Rao, A. G. and Sridevi Annapurna, Singh (2010) Production and characterization of a milk-clotting enzyme from Aspergillus oryzae MTCC 5341. Applied Microbiology and Biotechnology, 85. p. 1849.

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Abstract

Microbial milk-clotting enzymes are valued as calf rennet substitutes in the cheese industry. Aspergillus oryzae MTCC 5341 was identified to produce the highest milk-clotting activity during screening of 16 fungal strains. Solid state fermentation using wheat bran along with 4% defatted soy flour and 2% skim milk powder as substrate was optimal for growth of A. oryzae and production of the enzyme. Nearly 40,000 U/g bran of milk-clotting activity was present at the end of 120 h. The enzyme could be recovered by percolating the bran with 0.1 M sodium chloride for 60 min at 4°C. The decolorized enzyme preparation had high ratio of milk clotting to proteolytic activity. Affinity precipitation with alginate and subsequent elution with 0.5 M sodium chloride containing 0.2 M CaCl2 resulted in an enzyme preparation with specific activity of 3,500 U/mg and 72% yield. Optimum pH and temperature for activity of the enzyme were characterized as 6.3 and 55°C, respectively. Milk-clotting enzyme showed differential degree of hydrolysis on casein components. High ratio of milk clotting to proteolytic activity coupled with low thermal stability strengthens the potential usefulness of milk-clotting enzyme of A. oryzae MTCC 5341 as a substitute for calf rennet in cheese manufacturing.

Item Type: Article
Uncontrolled Keywords: Microbial rennet . Aspergillus oryzae . Solid state fermentation . Thermal stability . Immobilization . Casein components
Subjects: 500 Natural Sciences and Mathematics > 07 Life Sciences > 04 Microbiology > 04 Fungi
600 Technology > 08 Food technology > 16 Nutritive value > 05 Enzymes
500 Natural Sciences and Mathematics > 07 Life Sciences > 04 Microbiology
Divisions: Protein Chemistry and Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 25 Feb 2010 10:55
Last Modified: 01 Jul 2015 11:52
URI: http://ir.cftri.com/id/eprint/9340

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