Article

Thermostable α-amylase production by Bacillus subtilis entrapped in calcium alginate gel capsules

Department of Chemistry, Faculty of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
Enzyme and Microbial Technology (Impact Factor: 2.97). 08/2006; 39(4):690-696. DOI: 10.1016/j.enzmictec.2005.12.002

ABSTRACT Bacillus subtilis cells were immobilized by entrapment in calcium alginate gel capsules and the immobilized biocatalyst was used for the semi-continuous production of α-amylase. The α-amylase yield and operational stability of the immobilized system were increased by tailoring the capsules’ characteristics. Capsules prepared from 2% (w/v) sodium alginate and 3.5% (w/v) CaCl2 were the best support for cell immobilization, providing 2.5-fold higher α-amylase production in comparison to the freely suspended cells. Immobilized biocatalysts sustained 90% of their initial productivity over five sequential batches in a 10-day period, while amylase production by free cells declined sharply after the second use. Even higher operational stability was achieved when the capsules were treated with 2% (w/v) CaCl2 for 30 min before each batch. In this case the appearance of free cells in the medium was minimized and the immobilized system retained more than 85% of its initial efficiency after 15 fermentation batches, producing more than 1,450,000 units of extracellular α-amylase during this period.

Download full-text

Full-text

Available from: Maria Liakopoulou-Kyriakides, Jun 29, 2015
1 Follower
 · 
375 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The α-amylase (α-1-4-D-glucan glucanohydrolase; EC 3.2.1.1) secreted by Geobacillus stearotermophilus was purified and characterized. Maximum enzyme production was achieved after 24 h cultivation at pH 7.0 and 55°C. The enzyme was active in a broad temperature range, between 50 and 80°C, with an optimum at 70°C; and maximum activity was at pH 7.0. The enzyme was purified using 80% ammonium sulfate precipitation, dialysis, Sephadex G-100 gel filtration, and DEAE-cellulose column chromatography, with a 46-fold and 65% recovery and showed a MW of 63 kDa by SDS-PAGE. It was determined that the purified enzyme was stable at 50 and 60°C, and pH 7.0. It was determined that the purified enzyme was stable at 50 and 60°C at the end of 2 h. The enzyme retained 100% activity pH 7.0 at the end of 3 h. The enzyme was activated by Ca2+, Mn2+, and Triton X-100, but strongly inhibited by Cu2+, Zn2+, Fe2+, and Hg2+. The enzyme follows Michaelis–Menten kinetics with Km and Vmax values of 0.051 mM and 1.424 μmol/min, respectively.
    Starch - Starke 01/2014; 66(1-2). DOI:10.1002/star.201200279 · 1.40 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: α-amylase is an enzyme that has extensive applications in various industries, including starch liquefaction, brewing, food, paper, textile and pharmaceuticals. Among various sources of α-amylase, several microorganisms including fungi and bacteria have been shown to produce highly thermo stable α-amylase which holds significant industrial importance. In the present investigation, we have isolated and purified a novel halophilic α-amylase from Bacillus cereus MS6 bacteria from the effluent of a local paper industry. The bacterial growth conditions were optimized for the production of α-amylase by the fermentation process. The α-amylase thus produced was purified and then immobilization was carried out by the entrapment method in 2% sodium-alginate beads. The catalytic properties of the immobilized α-amylase were compared with that of the free enzyme. The optimum pH of the free enzyme was found to be 9.0, while that of immobilized enzyme was 10.0. The optimum temperature for the free and immobilized enzyme was 45oC and 50oC, respectively. The optimum substrate concentration for both free and immobilized enzyme was found to be 2.5%. The activity yield of the free and immobilized enzyme was 40% and 61.5%, respectively. The overall characterization data reveals an increase in the stability of the immobilized enzyme as compared to free α-amylase.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Extracellular α-amylase mass produced by Fusarium solani using mango kernel as substrate was immobilized in calcium alginate beads through entrapment technique. Maximum enzyme immobilization efficiency was achieved in 2mm size beads formed by 6.5 % (w/v) of sodium alginate in 2% (w/v) calcium chloride. The catalytic properties of the immobilized α-amylase were compared with that of free enzyme (soluble). The activity yield of the immobilized enzyme was 81±2% of the free enzyme. The immobilized enzyme showed optimum activity at pH 4.5-6.0 and temperature 40 ºC, in contrast to the free enzyme at 5.5 and 30ºC, respectively. Thermal stability of the immobilized enzyme was found to be more than the free enzyme over a longer time interval. The immobilized enzyme retained activity upto 20% of optimum even after 180 min. While the free enzyme lost its 80% activity after 60 min and lost total activity down to zero by 120 min. The kinetic constants, viz., KM (Michaelis constant), Vmax and activation energy were affected by immobilization. However, the immobilized α-amylase in calcium alginate beads supports its long term storage which has immense industrial applications.
    Journal of Environmental Biology 11/2012; 33(6):1021-1025. · 0.55 Impact Factor