Plant assisted bioremediation of petroleum hydrocarbon contaminated soil is considered an effective green technology whereby accelerated degradation occurs due to converged effect of microorganisms and plants. However, survival and growth of microbes and plants under stress conditions is challenging task for success of the technology. In this study, plant growth promoting bacteria containing 1-aminocyclopropane-1-carboxylate (ACC)-deaminase activity and tolerance to petroleum hydrocarbon contamination were used in association with alfalfa for bioremediation of petroleum hydrocarbon contaminated soil. Eight pre-isolated bacterial isolates from soil having previous history of petroleum contamination were used in convergence with alfalfa on sand soil which was artificially contaminated (10 g crude oil per kg-1 of coarse textured soil). Combined effect of bacteria and plants on the degradation of petroleum hydrocarbons under controlled conditions of light and temperature was observed for a period of 60 days. The results of the study revealed that four bacterial isolates Bacillus subtilis strain PM32Y, Bacillus cereus strain WZ3S1, Bacillus sp. strain SM73 and Bacillus sp. strain WZ3S3 in association with alfalfa significantly degraded petroleum hydrocarbons. The most significant biodegradation (47%) of petroleum hydrocarbons was recorded in the experimental unit receiving PM32Y inoculation in association with alfalfa. Biodegradation of petroleum hydrocarbons was 33% with alone inoculation (without alfalfa) of PM32Y. The study revealed that combined use of bacteria and alfalfa plant is more efficient than alone application of either bacteria or plants for degradation of petroleum hydrocarbons.
Keywords: ACC-deaminase; Alfalfa; petroleum hydrocarbons; plant growth promoting bacteria.
This study provides the evidence for phytoremediation and significant degradation of petroleum hydrocarbons by using plant growth promoting bacteria (PGPB), containing 1-aminocyclopropane-1-carboxylate deaminase (ACC-deaminase) in association with alfalfa (Medicago sativa L.). The most significant biodegradation of petroleum hydrocarbons was recorded with a new combination of Bacillus subtilis strain PM32Y in association with alfalfa.