Artificially obtained humic-like substances from chicken manure and symbionts in in vitro and in situ improvement of oil degradation in soil

Alkaline hydrolysate of chicken manure (HCM) containing artificially formed humic-like substances (HLSs) was investigated in combination with specially loaded cells (bacteria and microalgae) for oil degradation in soil. After 7 days in the laboratory experiment, the oil biodegradation efficiency in the polluted soil (50 g oil/kg soil) was 5–78% in 11 soil samples depending on the soil characteristics and used combination of additives. Higher level of oil-degradation corresponded to soil with high initial concentration of humic substances (HSs) (85–107 g/kg of dry matter). The best result in bioremediation (degradation of 82% of oil for 7 days) was achieved in experiment under field conditions with the similar initial oil pollution in the soil, when the HCM was used as additive (up to 220 mg HLSs/kg dry soil) in combination with an artificial symbionts composed of Rhodococcus erythropolis and Chlorella vulgaris cells. The introduction of HCM into oil-polluted soil with the mentioned cells led to an increase in all controlled enzymatic activities (peroxidase, dehydrogenase, phosphatase, protease, amylase, and urease) in the soil. The observed effects testified to activation of cell metabolic processes in the soil. As a result, the introduction of HCM in combination with artificial symbionts into the soil increased the rate of oil biodegradation under environmental conditions up to 1.8 times.

Graphical Abstract