LAUSR

Abstract α-amylase is a starch hydrolyzing enzyme which has many industrial applications. In the present study, α-amylase producers were isolated from farm soil in Egypt (Sadat City). Screening was done by iodine test, based on the clear zone around the sample in starch agar plates. The most potent isolate MK1 was identified (morphologically and biochemically) and confirmed by 16S rRNA gene sequence method. This sequence was deposited to the GenBank under accession number, B. subtilis strain-MK1 (MF614924). α-Amylase production parameters were optimized using one-factor-at-a-time (OFAT) and Response Surface methodology (RSM). The result obtained from OFAT showed 72.4U/ml of amylase activity which was 1.8- fold higher as compared to unoptimized conditions (40.3 U/ml). The most significant factors were identified and its values were optimized using Plackett-Burman (PB) and Central Composite (CC) design, respectively. Among thirteen independent variables tested in PB design, beef extract, MgSO4·7H2O, K2HPO4 and incubation time were the most significant on α-amylase production and showed positive effect. Whereas MnCl2·4H2O, soluble starch and culture pH showed negative effect on α-amylase production. The model validation was clear up on comparing the statistical predicted yield (140.14 U/ml) with the actual experimental yield (145.4 U/ml) of α-amylase which was closely related. The model showed higher amylase activity of 3.6 and 7.5-fold as compared to the basal and the initial media, respectively. Optimized medium by OFAT and RSM enhanced enzyme production by 7.5-folds confirming the need to optimize the production parameters to achieve maximum yield.