Chitinases de Bacillus isolés de milieux arides : Applications et perspectives en bioremédiation et biocontrôle

Abstract

This study investigates the chitinolytic potential of Bacillus species strains for the biodegradation of chitin and their broader biotechnological applications. A total of 39 bacterial isolates, collected from the rhizosphere of wheat and barley grown in arid regions of Algeria, were screened on chitin agar medium at pH 6. Six strains exhibited high enzymatic indices (ranging from 2 to 5), with Bacillus thuringiensis D1 and Bacillus subtilis D11 showing the highest chitinolytic activities in liquid culture (139.45 U/mL and 150.92 U/mL, respectively). Abiotic stress factors (pH, temperature, and salinity) revealed that both strains are neutrophilic, mesophilic (optimal at 37 °C), and in non-saline medium (less than 400 mM NaCl). Their enzymatic activity remained stable over a broad pH range (3–9), and was enhanced in the presence of Mn²⁺ and Fe²⁺ ions, highlighting their industrial potential. Furthermore, crude enzymatic extracts from D1 and D11 showed promising biotechnological applications. In vivo tests demonstrated partial inhibition of Fusarium graminearum and Botrytis cinerea infections in wheat seeds and strawberries. The enzymatic extracts also exhibited strong insecticidal activity against Anobiinae Vrillette on coriander (over 80% mortality). Additionally, significant degradation of shrimp waste was achieved, with weight loss reaching 50% and a notable release of N-acetylglucosamine. These findings highlight the potential of Bacillus D1 and D11 as strong candidates for industrial and ecological applications, particularly in biocontrol, organic waste valorization, and environmentally friendly enzyme production.