Digestate-Based Liquid Growth Medium for Production of Microbial Chitosan
2025
Silvia Crognale | Cristina Russo | Eleonora Carota | Ilaria Armentano | Federico Di Gregorio | Alessandro D’Annibale | Alessio Cimini | Maurizio Petruccioli
This study investigated the feasibility of using both the solid and the liquid fractions of waste from the anaerobic digestion process—the digestate—as a possible liquid growth medium for fungal production of chitosan. An enriched liquid phase (ELP), combining both fractions, and derived from mild acid hydrolysis treatment at 120 °C with 6% H<sub>2</sub>SO<sub>4</sub> (w/v) for 70 min, was screened for its ability to support biomass and chitosan production by 17 fungal strains. The best results were obtained with <i>Absidia blakesleeana</i> NRRL 2696 and <i>Rhizopus oryzae</i> NRRL 1510 cultures, which yielded chitosan volumetric productions of 444 and 324 mg L<sup>−1</sup>, respectively. The chitosan preparations of the former and the latter strain, characterized by infrared spectroscopy, elemental analysis, viscosimetry and thermogravimetric analysis, showed deacetylation degrees of 79% and 84.2%, respectively, and average viscosimetric molecular weights of around 20 and 5.4 kDa, respectively. Moreover, both fungal chitosan samples exerted significant antibacterial activity towards Gram-negative (i.e., <i>Pseudomonas syringae</i> and <i>Escherichia coli</i>) and Gram-positive (i.e., <i>Bacillus subtilis</i>) species.
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