Genetic characterization of bacteria in bioremediation of soil polluted by waste motor oil: safe vegetal consume

Abstract

Waste motor oil (WMO) is a mixture of insoluble aliphatic hydrocarbon molecules with chains between C11-C20 and C20-C35, as well as of aromatic, polycyclic and halogenated compounds. In Mexico, this mixture is classified as hazardous waste, according to the “General Law of Ecological Balance and Environmental Protection". WMO is generated in mechanical workshops due to use in agricultural machinery and its inadequate final disposal that occasion an environmental problem. WMO in soil has negative effects that limit agricultural production including health problem in humans. An alternative solution is biostimulation, first with biodetergents that emulsified them, followed of enrichment with a mineral solution that contents nitrogen, phosphorus, and potassium. The effective mineralization of WMO is based in the fact that soil is a source of diversity of bacteria able to eliminate WMO. The aims of this research were: i) to isolate and select bacteria capable oxidate WMO due that biodetergent and lipolytic activity and ii) the genetic identification of these soil bacteria involved in oxidation WMO. Results show that some microorganisms were isolated from soil contaminated by two concentrations of WMO, from soil contaminated by 60,000 WMO: Achromobacter denitrificans, a short Gram-negative rod, two species of the sporulated genus Gram-positive Bacillus, B. horneckiae and B. subtilis, and an actinomycete Gordonia amicalis, a Gram-positive coccobacillus. From soil contaminated by 80,000 ppm and WMO, another member of the Bacillus genus, B. cereus strain 2, was isolated and according to the molecular identification that places them as part of a metagenome it has the capacity to synthesize detergents and with ist lipolytic activity to oxidant WMO. These results support that in agricultural soils contaminated by waste motor oil there is a diversity of bacteria, which synthesize biodetergents simultaneously with lipolytic activity, both useful tools for soil bioremediation and the recovery of healthy plant productive capacity, safe for human and animal consumption.