Hydrocarbon-Degrading Consortium ZL for Oily Sludge Remediation: A Blueprint for Microbial Consortia Design

Rational design of specialized microbial consortia for targeted bioremediation remains a challenge, often relying on empirical screening rather than predictable principles. To bridge this gap, an innovative consortium design framework based on "specialized alkane degraders-multifunctional strains-biosurfactant (dirhamnolipid and surfactin) producers," was proposed. This framework was derived from the systematic deconstruction of a hydrocarbon-degrading consortium, ZL, comprising bacterial strains with high individual degradative capabilities. Under optimized conditions with glucose (20 g/L), monosodium glutamate (20 g/L), and trisodium citrate (10 g/L) as co-metabolic substrates, ZL achieved a hydrocarbon degradation rate of 66.22% in oily sludge within 15 days. ZL exhibited a wide range of hydrocarbon degradation capabilities, with C10-C40 degrading more efficiently than polycyclic aromatic hydrocarbons (86.19% > 55.80%). ZL rapidly and spontaneously produced biosurfactants within the first three days (E24 = 72%). During the remediation process, surface tension was reduced from 58.85 to 35.16 mN/m, emulsification activity (E24 > 65%) was comparable to the performance of 5% exogenous rhamnolipid alone (E24 = 67%). Microbial diversity analysis showed that ZL had more hydrocarbon-degrading strains and higher related metabolic and gene abundances than the indigenous microbiota. Metatranscriptomic analysis revealed the overall response of ZL and the functional division among its member strains. By comparing the functions of individual strains in single-strain culture and in ZL, a microbial consortium design framework and some suggestions were proposed. This study provides a mechanistic blueprint for designing microbial consortia for efficient oily sludge remediation.