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 01/2006; 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.

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