Fermentation of Lignocellulosic Substrates Enhances the Safety and Nutritional Quality of Flake Soil for Rhinoceros Beetle Rearing.

The rhinoceros beetle (Xylotrupes gideon) requires safe and nutritious flake soil substrate for commercial rearing in northern Thailand, yet optimal lignocellulosic formulations remain undefined. This study evaluated five flake soil formulations substituting lignin-rich cadamba sawdust (0-100%) with cellulose-rich corn stover, plus cattle manure and rice bran, fermented for 90 days. Fermentation engineered the cellulose-lignin-hemicellulose matrix, reducing lignin from 25.07% to 7.30% while enriching cellulose from 29.73% to 33.83% and hemicellulose from 6.67% to 17.42%. Increasing corn stover enhanced crude protein (5.46-7.53%) and nitrogen-free extract (24.17-34.14%), creating T1 (25% substitution) as the optimal cellulose-based composite for X. gideon rearing. Microbial analysis showed T1-T2 supported highest α-diversity and lactic acid bacteria enrichment, suppressing pathogens like Escherichia coli and Salmonella enterica. Fermentation degraded >99% glyphosate residues (from 106 mg/kg to <0.25 mg/kg or undetectable). T1 is recommended as the optimal, sustainable flake soil for X. gideon rearing, balancing nutrition, microbiology, and safety while valorizing agricultural wastes.