Abstract: The search for a polygalacturonase suitable for fallen leaf hydrolysis is crucial for accelerating the natural nutrient cycle. This study involved collecting corresponding samples to increase the possibility of obtaining target microorganisms, determining enzymatic characteristics to assess the adaptability of polygalacturonase, and hydrolyzing fallen leaves to measure the application potential of the isolated strain. In the study, a polygalacturonase-producing strain, F21-5, was isolated from decaying fallen leaves and identified asAspergillus fumigatusbased on morphological characteristics and internal transcribed spacer sequence analysis. The obtained F21-5 crude polygalacturonase showed an optimal pH of 5.5, retained more than 80% of its activity within the pH range of 4.0－6.0, and remained stable across pH 3.0－11.0. Furthermore, the enzyme exhibited maximum activity at 60－65 ℃ and maintained stability at 40 ℃. The activity of F21-5 crude polygalacturonase was markedly inhibited by Ca2+ and Cu2+ at the tested concentrations. Hydrolysis of fallen leaves increased the reducing sugar concentration by 503.47%±37.26% in leaves ofMagnolia denudata, 416.07%±0.48% inTectona grandisL.f., 227.03%±0.46% inArtocarpus heterophyllusLam., and 105.60%±0.27% inDracontomelon dao. These results demonstrate thatA. fumigatusF21-5 produces a robust polygalacturonase with strong hydrolytic activity, indicating its potential role in leaf degradation and natural nutrient cycling. Furthermore, polygalacturonase produced byA. fumigatusF21-5 represents a high-potential biocatalyst for industrial-scale pectin bioconversion applications.

Key words: polygalacturonase, fallen-leaf hydrolysis;Aspergillus fumigatus, strain isolation and identification, enzymatic characteristics