Enzymatic Degradation of Cryptosporidium spp. Oocysts: A Combined In Silico and In Vitro Study

Proteases are widely studied hydrolases as "green technologies" for degrading structures within complex matrices, although combining different classes poses challenges for catalytic stability. To the best of our knowledge, this is the first study to specifically evaluate the biochemical control of Cryptosporidium spp. oocysts using plant- and microbial-derived proteases. This study evaluated the compatibility and sanitizing potential of the microbial serine protease subtilisin Carlsberg (HPF-1SCA) and the plant cysteine protease papain (1PPP), both individually and in a 15% (w/v) combination, hypothesizing a synergistic effect due to their distinct catalytic specificities, as a potential biochemical approach to reduce contamination by these zoonotic protozoa of global importance, which are highly resilient to conventional disinfectants. The experimental design comprised five distinct treatment groups: a negative control (distilled water), a positive chemical control (0.04% v/v NaClO), treatment with isolated papain (15% w/v), treatment with isolated microbial HPF formulation (15% w/v), and a combined treatment using both enzymes simultaneously (15% w/v each). Concurrently, an in silico molecular docking investigation was conducted to elucidate the predicted binding scores, structural compatibility, and preferential binding mechanisms of these enzymes toward the Cryptosporidium Oocyst Wall Protein (COWP). In vitro compatibility assays revealed an immediate antagonistic effect due to mutual proteolysis, reducing overall proteolytic activity by 45% after 72 h. Despite this antagonism, the enzyme mixture (G5) and the isolated microbial protease (G4) achieved a 93% reduction in oocysts, equivalent to the conventional 0.04% NaClO treatment (G2), while papain (G3) achieved 65%. All these results represented statistically significant efficacy (p < 0.01) compared to the negative control (G1). In silico molecular docking studies provided a structural predictive basis for the experimental data, suggesting that subtilisin Carlsberg (HPF-1SCA) exhibits more favorable predicted binding scores and structurally compatible interfaces, compared to papain, particularly toward the major oocyst structural proteins COWP8 (estimated ΔG = -15.2 kcal·mol^-1) and COWP6 (estimated ΔG = -13.3 kcal·mol^-1). This provides robust evidence for initial target recognition and molecular anchoring, although these static models do not definitively confirm catalytically productive cleavage conformations. In summary, this in vitro proof-of-concept demonstrates that microbial proteases show promise for the biochemical destabilization of oocysts without generating toxic chlorinated byproducts. While these baseline findings align with the One Health concept, future field-scale validations assessing enzyme stability under variable environmental conditions and in vivo infectivity assays are required before practical application in sanitation protocols.