Abstract
In the present study, 20 different strains of Alkalibacillus flavidus were isolated from soils of industrial, agricultural and mountainous ranges of salt affected areas. After preliminary and secondary screening, isolate Isl-3 was selected as a better producer (5.25 ± 0.52 IU/g) of acetyl xylan esterase (AcXE). The wild-type Isl-3 was mutated to improve its hydrolytic potential by treating it with different EMS concentrations (0.25–1.5 mM). A relatively better enzyme activity (18.95 ± 0.95 IU/g) was observed at 0.5 mM EMS conc. The mutagenic exposure time was varied from 5 to 30 min, and a mutant strain (EMS-t3 was selected as it provided maximum enzyme activity (19.47 ± 0.97 IU/g) in 15 min. The resistance in EMS-t3 was developed by adding low-levels of l-cysteine HCl as a repressing agent. The enzyme activity of wild-type Isl-3 was compared with the putative mutant strain EMS-cys2 in semi-solid culture of linseed meal. The maximum enzyme activity (21.15 ± 1.05 IU/g) was obtained at substrate conc. of 7.5 g/50 ml of MSS by the mutant strain EMS-cys2. An increase in enzyme activity was noticed by both the strains when physical parameters including moisture content (100 ml), time of incubation (48 h), initial pH (9.5) and temperature (45 °C) were optimized. Overall, there was up to 6.8-fold increase in enzyme activity of mutant strain than that of wild-type. The substantial enhancement in enzyme activity by the mutant strain A. flavidus EMS-cys2 (34.65 ± 1.53 IU/g) is highly significant (HS, p ≤ 0.05) and could be a viable alternative (LSD ~ 0.046) for the routine batch culture process.
Published Version
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