APPLICABILITY OF WOOL COVALENT BONDED Bacillus circulans 25 CELLS FOR MILK-CLOTTING ENZYME PRODUCTION BY BATCH, REPEATED BATCH AND CONTINUOUS PROCESS

Abstract

The production of milk-clotting enzyme (MCE) by free and immobilized Bacillus circulans 25 cells was investigated. The investigation evaluates cell immobilization through entrapment and covalent binding to different carriers. B. circulans 25 cells immobilized covalently via glutaraldehyde (cross-linker) to natural wool exhibited higher effectiveness factor (0.76) compared to other carriers. Immobilized cells produce maximum level of MCE and highest ratio of milk-clotting activity/proteolytic activity (MCA/PA) after 24 h using 0.4g wet weight cells/g wool. In batch operation, decreasing biomass loading to 0.2 g enhanced the MCA/PA ratio and specific productivity by 5.94 and 59.88%, respectively. Immobilized cells on natural wool as an effective and suitable carrier were able to produce the same level of MCA, productivity and MCA/PA ratio for 9 repeated cycles (216 h). Under continuous operation immobilized cells in a packed-bed bioreactor were able to keep producing MCA with MCA/PA ratio for about 7 days at the same level. Moreover, continuous operation demonstrates a very good productivity of 0.385 KU/L/h, which is higher than the other production systems by 7.0-11.7 fold. Immobilized B. circulans 25 cells proved to be fully capable of continuous MCE production in a packed-bed bioreactor.

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“…MCE from B.circulans 25 has been produced according to the previous work (Ahmed et al, 2018). The medium used for MCE production had the following composition (g/L): lactose 20, yeast extract 1, peptone 1, K2HPO4 2 and MgSO4.7H2O 0.25, and the pH was adjusted to 6.0 prior to sterilization.…”

Kinetic, Catalytic and Thermodynamic Properties of Immobilized B.Circulans 25 Milk Clotting Enzyme on Activated Chitosan Polymer and Its Ability to Form Milk Curds

“…MCE from B.circulans 25 has been produced according to the previous work (Ahmed et al, 2018). The medium used for MCE production had the following composition (g/L): lactose 20, yeast extract 1, peptone 1, K2HPO4 2 and MgSO4.7H2O 0.25, and the pH was adjusted to 6.0 prior to sterilization.…”

Kinetic, Catalytic and Thermodynamic Properties of Immobilized Milk Clotting Enzyme on Activated Chitosan Polymer and its Application in Cheese Making

“…Milk clotting enzyme from Bacillus circulans 25 has been produced according to the previous work (Ahmed et al 2018). The medium used for MCE production had the following composition (g/L): lactose 20, yeast extract 1, peptone 1, K 2 HPO 4 2 and MgSO 4 .7H 2 O 0.25.…”

“…Various carriers have been used for immobilization e.g. polyacrylic (Esposito et al 2016), alginate-pectate (Narwal et al 2016), wool (Ahmed et al 2018), basalt (Ahmed et al 2019) and magnetic chitosan (Abdella et al 2020).…”