Hermetia illucens L. (Diptera: Stratiomyidae) has been considered as a biological backbone of the environment for bioconversion of organic waste to useful bioproducts, such as insect protein for animal feed and bioactive compounds. The bioconversion processes by this insect include all types of organic waste, except cellulosic material, which remains unpalatable for this insect. Manure is one of the natural substrate for H. illucens, however, its lower bioconversion efficiency is the main limitation. Thus, the objective of this study was to partially hydrolyze the cellulosic materials using different microbial fermentation approaches to make them useable by the insect for nutrition and higher biomass yield. The mixed microbial fermentation processes involve fungi and whey as sources of probiotics, amino acids, vitamins, and various microbial growth factors has been implemented. Manure was supplemented with whey and effective microorganisms derived from bokashi to optimize its nutritional value. Different agricultural wastes fermented with various fungi and whey industrial products were tested as nutritional substrates for insect rearing, as revealed by biological, histological, biochemical, and molecular parameters. The taxonomic identity of the insect was confirmed based on its mo lecular barcode of cytochrome oxidase (COI) sequence, as deposited in GenBank with accession # PP813749. The results indicated that media treated with whey proteins produced the highest measurements compared to other media regarding larval and prepupal biomasses. The highest protein (265.9 mg/ml), lipid (771.1 mg/ml), and carbohydrate (1905.5 mg/ml) contents of the insect biomass were reported on wheat straw and onion waste. From the histochemical analysis, the highest intensities of proteins, carbohydrates, and lipids were 44.1 %, 50.1 %, and 47.1 %, respectively, that closely matched the biochemical criteria. The highest activity of ALT, AST and protease were 144.4 U/ml, 90.2 U/ml, and 8.6 U/ml, respectively, in larvae fed on wheat straw fermented with whey. The activities of amylase and lipase were 125.7 U/ml and 74 U/ml for larvae fed on onion waste and wheat straw, respectively, fermented with whey. The biomass of the insect was confirmed by RT-qPCR analysis of selected rate-limiting growth markers. The highest amino acid contents in larvae were observed in those fed on onion waste fermented with whey. The antioxidant activity of the larvae was significantly increased when grown on onion waste fermented with whey, as indicated by FRAP and DPPH analyses. The chicken manure amended with bokashi, and pigeon manure supplemented with whey recorded the highest larval and prepupal biomass by 13 % increment, the protein, carbohydrate, and lipid content were increased by 2 %, 5 %, and 42 %, respectively.