Biological pretreatment of Eichhornia crassipes (water hyacinth) by Alternaria alternata ANF238 and optimization of growth factors for enhanced delignification

The current study investigated the biological pretreatment of water hyacinth by the fungus Alternaria alternata ANF238 with the analysis of delignification level within the water hyacinth biomass as the focal point. Additionally, an effort to enhance the efficiency of lignin degradation was also done by optimizing various growth factors including temperature, moisture content, carbon sources, inducers as well as their concentrations. The highest level of lignin reduction, amounting to 77.14%, was achieved at 35 °C following 35 days of pretreatment. This was obtained when the basal medium supplemented with 1.0% mannitol as a carbon source and 3 mM MnSO₄ as inducer and moistening agent was applied under solid-state fermentation conditions. Structural profiling of water hyacinth biomass by SEM, XRD, and FTIR, both pre and posttreatment, revealed significant microstructural changes obtained during the biological pretreatment process. Thus, our findings demonstrate the lignin-degrading capabilities of Alternaria alternata ANF238 making it an industrially suitable microbe for delignification of both water hyacinth as well as other sustainable feedstocks.