The global use of chemical fertilizers has risen dramatically, resulting in serious issues concerning environmental pollution and human health. Consequently, it is crucial to replace chemical fertilizers with organic alternatives. Utilizing organic fertilizers in agriculture not only enhances soil fertility but also positively impacts the physical characteristics of the soil. Key sources of organic matter in the soil include animal manure, plant residues, sewage sludge, and compost derived from urban waste, which have garnered increased attention due to the significance of organic farming. Biomass from agricultural by-products, grasses, wood, forest debris, and municipal solid waste is recognized as renewable, sustainable, and cost-effective resources in lignocellulosic conversion industries. The enzymes cellulase and xylanase represent two primary categories of holocellulase enzymes that facilitate the hydrolysis of lignocellulosic materials. Fungi from the Trichoderma genus are among the most effective producers of these enzymes. Sugarcane bagasse serves as an excellent substrate for the production of humic acid and various enzymes through fermentation processes. In this research, a biological system utilizing Trichoderma fungi was employed to generate humic acid from sugarcane bagasse, an agricultural waste product. To assess the enzymatic activity of different Trichoderma isolates and their interactions, a total of 210 isolates were analyzed. Qualitative assessments revealed that these isolates exhibited cellulase and xylanase activities exceeding 90%. Quantitative eva‎luations showed that the xylanase activities for isolates T7-7 and M55-2 were 1.86 U/mL and 1.78 U/mL, respectively, while the cellulase activities for isolates GL67-2 and T5-3 were 0.528 U/mL and 0.526 U/mL, respectively. The isolate GL93 demonstrated the lowest enzyme activity, with 0.052 U/mL xylanase and 0.002 U/mL cellulase. The results suggested that Trichoderma isolates capable of producing cellulase and xylanase on a sugarcane bagasse substrate could positively influence the biological process of humic acid production. selected strains were utilized for the extraction of humic acid. Findings indicated that the treatment inoculated with strain GL67-2 yielded the highest levels of humic acid at pH 7 over a 28-day period when compared to control samples. The quality of the extracted humic acid samples was eva‎luated using infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and elemental analysis for comparison with a commercial sample. The FTIR results indicated a significant correlation between the extracted samples and the commercial one.

حسين شريعتمداري , مژگان كوثري

حسين قنواتي

محمدعلي حاج عباسي جورتاني , حميدرضا عشقي زاده