Amylase alcaline de Bacillus issus des sols arides : potentiel enzymatique de Bacillus thuringiensis B16 et application dans la détergence et l’agroalimentaire.

Abstract

This work is part of the biotechnological valorization of Bacillus strains isolated from various Algerian soils, with the objective of producing alkaline amylases stable under harsh physicochemical conditions. Thirty-nine strains (n = 39) were screened on starch agar at pH 10, among which six (B16, B21, D13, D7, Ba7, Ba9) exhibited the highest enzymatic index values. Quantitative assays in liquid medium revealed enzyme activities ranging from 48 to 67 U/ml, with good residual stability, particularly in strains B21, B16, and D13.The stability of the enzyme was further investigated under various abiotic stresses, including extreme temperatures (30–80 °C), pH variations (6–12), and chemical agents (H₂O₂, SDS, NaCl, EDTA). Multivariate analysis identified strain B16 as the most robust, maintaining residual activity above 90% under most of the tested conditions. The addition of specific metal ions (Co²⁺, Zn²⁺, Ca²⁺) significantly enhanced amylase activity at pH 10, reaching up to 72 U/ml in the presence of cobalt. Finally, the enzymatic extract from strain B16 demonstrated promising applications, including detergent activity against starchy stains, juice clarification, and improvement of bread organoleptic properties. These findings confirm the industrial potential of alkaline amylases produced by Bacillus, particularly in the detergent, food processing, and starch waste treatment sectors.