Production of acid-stable and high-maltose-forming α-amylase of Bacillus acidicola by solid-state fermentation and immobilized cells and its applicability in baking.

Among matrices used for immobilizing Bacillus acidicola cells [calcium alginate, chitosan + alginate, scotch brite, and polyurethane foam (PUF)], α-amylase production was highest by PUF-immobilized cells (9.1 U ml(-1)), which is higher than free cells (7.2 U ml(-1)). The PUF-immobilized cells could be reused over seven cycles with sustained α-amylase production. When three variables (moisture, starch, and ammonium sulfate), which significantly affected enzyme production in solid-state fermentation (SSF), were optimized using response surface methodology, 5.6-fold enhancement in enzyme production was attained. The enzyme production in SSF is 3.8-fold higher than that in submerged fermentation. The bread made by supplementing dough with α-amylase of B. acidicola scored better than those with the xylanase of Bacillus halodurans and thermostable α-amylase of Geobacillus thermoleovorans.