Isolation, Characterization, and Byproducts Analysis of Six Oil-Degrading Strains for Rural Food Waste Treatment

The composting of food waste (FW) in rural areas can be enhanced by utilizing effective oil-removing strains. This study investigates the screening process, oil removal performance, and byproducts of efficient soybean oil-degrading microbial strains. The initial strain sources were collected during the high-temperature phase of aerobic FW composting. After six stages of gradient domestication with oil concentrations ranging from 1.6 to 16 g/L, the oil removal efficiency (RE) of the mixed strains exceeded 90% within 4 days. Through gradient dilution and separation, three fungi and three bacteria with effective oil-removing capabilities were identified. At an oil concentration of 10 g/L, the oil RE of four strains (Simplicillium cylindrosporum, Fusarium proliferatum, Agrobacterium tumefaciens, and Pseudomonas geniculata) exceeded 93% within 6 days. Notably, Pseudomonas geniculata achieved the high 95% oil RE within 4 days, demonstrating the highest efficiency among the six strains tested. Additionally, F. proliferatum and Luteibacter rhizovicinus exhibited the strongest surfactant production capabilities among the fungi and bacteria, respectively. The byproducts of the degradation process were analyzed in detail using gas chromatography for the first time, revealing six types of volatile fatty acids. Both propionic acid and n-valeric acid were completely degraded by all six strains, while acetic acid requires careful management to prevent environmental pollution. Except for acetic acid, A. tumefaciens was able to completely degrade the other five acids, making it an environmentally friendly option. The strains identified in this study hold significant potential for improving processes such as rural FW composting, oil-containing wastewater treatment, and other oil-containing waste management.