Microbial-Enhanced Peel and Seed Wastes of Dimocarpus longan Bokashi Fertilizers: Unlocking Soil Health and Bioactive Constituents in Trigonella foenum-graecum

Abstract

Abstract This study evaluates a modified Bokashi fermentation system utilizing a specific microbial consortium ( Saccharomyces cerevisiae , Lactococcus lactis , and Rhodopseudomonas palustris ) to bio-transform Dimocarpus longan (longan) fruit peels and seeds into bio-fertilizer. The fermentation stability was assessed via total organic matter (OM) and carbon-to-nitrogen (C/N) ratios. The resulting bio-compost teas, Longan Peel (LP), Longan Seed (LS), and a 1:1 mixture (LP: LS), were applied at 1% (w/v) to Trigonella foenum-graecum (fenugreek) in a pot experiment. The 15-day-old seedlings were collected for analysis. All fermented treatments significantly enriched soil nutrients and optimized the C/N ratio compared to the control. The LS treatment yielded the highest nutrient concentrations, while the LP: LS treatment resulted in the highest microbial activity, specifically increasing fungal counts (e.g., Aspergillus , Cladosporium , and Penicillium spp.) and bacterial/actinomycete populations. Physiologically, LP: LS-treated fenugreek exhibited the highest increases in chlorophyll pigments, carbohydrates, protein content, and secondary metabolites (phenolics and flavonoids contents). Furthermore, RT-PCR analysis confirmed the up-regulation of key biosynthetic genes, including MVK , PAL , and FLS (polyphenolic/terpenoid pathways) and CHLH (chlorophyll biosynthesis). Oxidative stress, measured via malondialdehyde (MDA) levels, remained within control ranges, indicating no phytotoxicity. These data demonstrate that the S. cerevisiae , L. lactis , and R. palustris Bokashi system effectively stabilizes longan waste into a nutrient-rich bio-fertilizer. The up-regulation of metabolic genes and improved soil microbial profiles provide a technical basis for using this waste-to-resource strategy as a measurable alternative to synthetic chemical inputs in sustainable agriculture. Graphical Abstract