Screening for chitin degrading bacteria in the environment of Saudi Arabia and characterization of the most potent chitinase from Streptomyces variabilis Am1

• Published in: Scientific reports 2023-07, Vol.13 (1), p.11723-11723, Article 11723
• Main Authors: Kotb, Essam, Alabdalall, Amira H., Alghamdi, Azzah I., Ababutain, Ibtisam M., Aldakeel, Sumayh A., Al-Zuwaid, Safa K., Algarudi, Batool M., Algarudi, Sakina M., Ahmed, Asmaa A., Albarrag, Ahmed M.
• Format: Article
• Language: English
• Subjects: 631/1647/2230; 631/1647/2234; 631/326/2522; 631/45/607; Antifungal activity; Bacteria; Biodegradation; Biotechnology; Carbon sources; Catalysis; Cellulose; Chitin; Chitinase; Chitinolytic bacteria; Chitosan; Edetic acid; Galactose; Humanities and Social Sciences; Ions; Microorganisms; multidisciplinary; pH effects; Phytopathogenic fungi; Reagents; Science; Science (multidisciplinary); Streptomyces; Streptomyces variabilis; Thermal stability; Yeasts
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-023-38876-2

Forty-six promising chitinolytic isolates were recovered during a screening for chitinolytic bacteria in the environment of Saudi Arabia. The top three isolates belonged to the genus Streptomyces . Streptomyces variabilis Am1 was able to excrete the highest amount of chitinases, reaching the maximum at 84 h with 0.5% yeast extract and nitrogen source and 2% galactose as a carbon source. Purification of chitinase by DEAE-Cellulose and Sephadex G 75 improved the specific activity to 18.6-fold and the recovery to 23.8% and showed a mass at 56 kDa. The optimal catalysis of the purified chitinase was at 40 °C and pH 8 with high thermostability and pH stability as reflected by a midpoint temperature value of 66.6 °C and stability at pH 4–9. The protein reagents SDS, EDTA, and EGTA significantly inhibited the enzyme and the EDTA-chelated chitinase restored its activity after the addition of Fe 2+ ions suggesting a metallo-chitinase type with ferric ions as cofactors. Chitinase exerted high antifungal activity against some phytopathogenic fungi. Interestingly, the tested Streptomyces were able to produce chitosan nanocubes along with chitosan from chitin degradation which may be an additional power in their antifungal activity in nature. This work also reveals the importance of unexplored environments as a pool of promising microorganisms with biotechnological applications.