Marine chitinase BtChi disrupts cell wall integrity in Candida albicans and non-albicans species by chitin targeting and release of chitooligosaccharides

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Abstract Increasing resistance to conventional antifungal drugs against Candida species, along with the limited availability of drug targets due to similarities between fungal and human cellular processes, necessitates alternative antifungal strategies. Chitin, a key polysaccharide component of the fungal cell wall, represents an attractive antifungal target. In this study, a chitinase ( Bt Chi) derived from a marine bacterium was expressed and purified and evaluated for antifungal activity against Candida species by targeting cell wall chitin. The purified Bt Chi (71 kDa) with a total activity of 438.6 U exhibited broad species specific antifungal activity, with MIC ranging from 7.8 to 250 µg/mL. Notably, Candida auris showed increased susceptibility, with MIC 50 and MIC 90 values of 3.9 µg/mL and 7.8 µg/mL, respectively. Bt Chi demonstrated fungicidal like activity, achieving ≥ 3 log 10 CFU/mL reductions from 12 to 20 h for most species except for C. parapsilosis and C. auris , which showed lower reductions of 1.67 and 0.4 log 10 CFU/mL, respectively. Microscopic analysis revealed cell wall damage, while HPLC noted the release of monomeric, dimeric, and trimeric chitooligosaccharides, suggesting chitin degradation. Key points ∙ BtChi chitinase exhibited species specific antifungal activity ∙ BtChi showed species-specificspecies dependent fungicidal effects in killing kinetics against Candida albicans and non-albicans species ∙ BtChi targets chitin in the Candida cell wall, releasing chitooligosaccharides

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