Sulfation of Sugarcane-Bagasse Xylan: Process Optimization, Physicochemical Properties and In Vitro Anticoagulant Activity

Xylan sulfates are established anticoagulant polysaccharides, but their preparation requires balancing sulfate substitution and product recovery. Sugarcane-bagasse xylan was sulfated using sulfur trioxide–pyridine complex (SO3·Py), 4-dimethylaminopyridine (DMAP), and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDCI). An entropy-weighted five-factor Box–Behnken design jointly optimized degree of substitution (DS) and isolated, DS-adjusted yield, assigning respective weights of 0.570 and 0.430. Pareto analysis identified a trade-off between increasing DS and decreasing yield, while accounting for model uncertainty produced little change in the selected optimum. Validation used adjusted reagent-to-xylan mass ratios of 0.2, 3.2, and 2.2 g/g for DMAP, SO3·Py, and EDCI, respectively, at 50.7 °C for 3.8 h. Three independent batches yielded DS = 1.53 ± 0.01, yield = 78.0 ± 0.1%, and a composite score of 0.792 ± 0.008, within the model’s 95% prediction interval. Operational water solubility increased from 21.2 to 96.8–130.4 mg/mL after sulfation, alongside changes in aqueous aggregation and rheology. In citrated sheep plasma, the derivatives prolonged activated partial thromboplastin time and thrombin time with increasing concentration. Responses increased across the derivative series, in which DS and the reported apparent molar mass covaried. These results provide a basis for balancing substitution and product recovery and comparing the water solubility and in vitro anticoagulant responses of the resulting derivatives.