Abstract
Three strains, Bacillus subtilis B1, B. subtilis B18 and Bacillus thuringiensis B12,were screened from wheat bran to produce milk-clotting enzyme. Among them, B. subtilis B1 exhibited considerable milk-clotting activity with low proteolytic activity. After response surface methodology optimization, milk-clotting activity wasimproved from 782 SU ml-1 to 1129.05 ± 74.55 SU mL-1 with a small inoculum size (0.130%, v/v). The optimized medium contained glucose (16.2 gL-1), wheat bran (30 gL-1), NaCl (5 gL-1), MgSO4·7H2O (5 gL-1), KH2PO4 (2 gL-1) and CaCO3 (3 gL-1). The milk-clotting enzyme from B. subtilis B1 has the optimum pH 5.5 and CaCl2concentration 50 mmol L-1. It is completely inactivated after 5 min at 70°C. The result showed that B. subtilis B1 was a promising strain for industrial milk-clotting enzyme production. Key words: Milk-clotting enzyme, Bacillus subtilis, submerged fermentation, wheat bran.
Highlights
Rennet (E.C. 3.4.24.4) from calf stomach is the largest single proteolytic enzyme in food processing
Since wheat bran is the main part of koji in China, the enzymeproducing bacteria from glutinous rice wine seems to come from wheat bran (Wang et al, 2009)
B. subtilis B1 was considered as a promising safe producer due to its high milk-clotting activity (MCA) with low proteolytic activity (PA) and B. subtilis was generally regarded as safe by Food and Drug Adiministration (Schallmey et al, 2004)
Summary
Rennet (E.C. 3.4.24.4) from calf stomach is the largest single proteolytic enzyme in food processing. Only few research work on bacteria are reported, wild bacteria with a high milk-clotting activity (MCA) in submerged fermentation show a great potential, due to shorter fermentation period, larger capacity of extracellular secretion and higher material utilization ratio (Dutt et al, 2008) Some bacteria, such as Bacillus subtilis, Bacillus licheniformis and Enterococcus faecalis, have been suggested as potential rennet substitutes (Sato et al, 2004; Ageitos et al, 2007; Dutt et al, 2008). The isolated strains were further inoculated in nutrient broth medium to detect MCA They were grown and maintained at 35 ± 0.5 and 4°C, respectively, on agar slant (glucose, 20 g L-1; yeast extract, 10 g L-1; agar, 20 g L-1).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
