Response of Portulaca oleracea biomass and its rhizospheric microbiome to the application of solid and liquid slumgum from beekeeping industry transformed with Penicillium chrysogenum

Abstract Background and aims Slumgum, a by-product of the beeswax-rendering process, is a nutrient-rich organic waste with potential as a sustainable fertiliser. Unlike chemical fertilisers, which can degrade soil health and contribute to environmental pollution, slumgum may improve soil structure, enhance microbial activity, and support long-term soil fertility. This study assessed, for the first time, the effects of both solid and liquid slumgum, either transformed with Penicillium chrysogenum and non-transformed, on purslane ( Portulaca oleracea ) biomass and soil rhizosphere microbial communities. Methods The experiment involved applying different slumgum treatments to purslane plants, followed by the analysis of shoot biomass and foliar phosphorous content. Soil enzymatic activities related to carbon, nitrogen, and phosphorus cycles were measured. Additionally, bacterial and fungal community composition, diversity, and functional guilds in the rhizosphere were described. Results Both transformed solid and liquid slumgum along with untransformed liquid slumgum treatments increased purslane shoot biomass (by 60–77%) and foliar phosphorous content (by 87–100%) compared to the control. Slumgum treatments modified the microbial community composition, increasing saprotrophic fungi and reducing plant pathogens. Transformed solid slumgum also enhanced enzymatic activities involved in nutrient cycling, whereas the untransformed solid slumgum treatment promoted bacterial genes associated with denitrification. Conclusion Our findings highlight the potential of slumgum, particularly in its transformed forms, as a sustainable alternative to chemical fertilisers. Its application may improve soil fertility and crop productivity while reducing environmental impact. Further studies should investigate its long-term effects under field conditions and evaluate its economic feasibility.