Abstract
Chitosanase plays a vital role in bioactive chitooligosaccharide preparation. Here, we characterized and prepared a potential GH46 family chitosanase from Bacillus atrophaeus BSS. The purified recombinant enzyme Csn-SH showed a molecular weight of 27.0 kDa. Csn-SH displayed maximal activity toward chitosan at pH 5.0 and 45°C. Thin-layer chromatography and electrospray ionization–mass spectrometry indicated that Csn-SH mainly hydrolyzed chitosan into (GlcN)2, (GlcN)3, and (GlcN)4 with an endo-type cleavage pattern. Molecular docking analysis demonstrated that Csn-SH cleaved the glycoside bonds between subsites −2 and + 1 of (GlcN)6. Importantly, the chitosan hydrolysis rate of Csn-SH reached 80.57% within 40 min, which could reduce time and water consumption. The hydrolysates prepared with Csn-SH exhibited a good antifungal activity against Magnaporthe oryzae and Colletotrichum higginsianum. The above results suggested that Csn-SH could be used to produce active chitooligosaccharides efficiently that are biocontrol agents applicable for safe and sustainable agricultural production.
Highlights
Chitin is the second largest natural polysaccharide after cellulose and exists widely in arthropods exoskeletons, fungi, and insect intestinal mucosa
According to the sequence alignments and phylogenetic tree analysis, the chitosanases of GH46 family were grouped into five clusters A, B, C, D, and E, and almost all chitosanases in cluster B were derived from Bacilli (Viens et al, 2015)
The phylogenetic tree analysis results indicated that Csn-SH was a novel member of cluster B (Figure 1A) and showed higher homology with the chitosanase from Bacillus amyloliquefaciens MJ-1 (Hong and Kang, 2006)
Summary
Chitin is the second largest natural polysaccharide after cellulose and exists widely in arthropods exoskeletons, fungi, and insect intestinal mucosa. Chitosan exhibits good biodegradability and biocompatibility and is nontoxic and soluble in weak acid. It has been widely used in gene therapy, drug delivery, wound repair, and microbial growth inhibition (Yang et al, 2020). COSs are Antifungal Chitooligosaccharides Prepared With Csn-SH nontoxic, water-soluble, and biocompatible and have been widely used as antitumor (Jiang et al, 2020), drug-delivery (Wang et al, 2021a), antimicrobial (Silva et al, 2021), antifungal (Zhou et al, 2020), immune-activating (Zhang et al, 2021), and food preservation agents (Dutta et al, 2012)
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