Enhanced Growth of Mungbean and Remediation of Petroleum Hydrocarbons by Enterobacter sp. MN17 and Biochar Addition in Diesel Contaminated Soil

Abstract

Petroleum hydrocarbon (PHC) contamination of soil is a widespread global environmental concern due to the persistence and recalcitrant nature of PHCs. The PHCs are highly toxic and their removal from the terrestrial ecosystem is necessary to maintain soil as well as human health. Here, a pot experiment was performed to examine the impact of Enterobacter sp. MN17 and biochar addition on the growth of mungbean plants and PHCs removal from diesel-polluted soil. For this purpose, soil was contaminated artificially with diesel to achieve a final concentration of 5000 mg kg−1. Untreated and Enterobacter sp. MN17 treated mungbean seeds were sown in pots. Sugarcane bagasse biochar was applied as an amendment in respective pots along with the recommended levels of essential nutrients. Results showed that PHCs significantly suppressed the seedling emergence as well as agronomic and physiological attributes of mungbean as compared to un-contaminated controls. However, the co-application of Enterobacter sp. MN17 and biochar significantly reduced the phytotoxicity of PHCs to mungbean plants and effectively increased the seedling emergence, shoot and root length, shoot fresh and dry biomass, root fresh and dry biomass of plants up to 24%, 54%, 52%, 52%, 54%, 55% and 60%, respectively as compared to controls. Similarly, 30%, 57%, 64%, 36% and 57% increase in chlorophylls contents, transpiration rate, stomatal conductance, sub-stomatal conductance, and photosynthetic rate, respectively were observed in their combined application as compared to respective controls. Furthermore, the co-addition of biochar and Enterobacter sp. MN17 could remove 69% and 85% higher PHCs from unplanted and planted pots, respectively, than that of their respective controls. Our results suggest that the co-application of biochar and Enterobacter sp. MN17 may be useful in enhancing plant growth and eliminating PHCs from contaminated soil.

Isolation and Characterization of Oil-Degrading Enterobacter sp. from Naturally Hydrocarbon-Contaminated Soils and Their Potential Use against the Bioremediation of Crude Oil

“…This impact may be due to disturbances in water and nutrient absorption caused by oil in the soil, as well as soil nitrogen, and phosphorus depletion [46]. These results are in accordance with previous published studies [1,38,47] reporting that root morphology and plant biomass were reduced in soil contaminated with petroleum hydrocarbons. Plant growth and photosynthesis pigments-i.e., chlorophyll contents-may have been hindered by the presence of toxic petroleum hydrocarbon compounds [10].…”

Biochar and Bacillus sp. MN54 Assisted Phytoremediation of Diesel and Plant Growth Promotion of Maize in Hydrocarbons Contaminated Soil

“…The microbial optical density (OD) was determined by using a spectrophotometer, and the OD value was adjusted to 0.5 (i.e., 10 8 -10 9 CFU mL −1 ) [23]. Maize seeds were surface-sterilized by following the protocol described by Ali et al [20]. The surface-sterilized seeds were then immersed in Bacillus sp.…”

“…Agronomic attributes such shoot and root lengths, fresh and dry weights of shoot and root were determined and recorded using suitable instruments following standard protocols [20]. Different physiological parameters including photosynthetic rate (A), stomatal conductance (Gs), substomatal conductance (Ci) and transpiration rate (E) were taken using portable infrared gas analyzer (IRGA) (LCA-4, Germany).…”

“…Several isolated microbes of genera Achromobacter, Bacteroides, Acinetobacter, Microbacterium, Actinobacteria, Pseudomonas, Arthrobacter, Cellulomonas and Azobacter are known to be effective for PHCs degradation [15,18,19]. They produce a variety of enzymes to regulate the degradation pathways through different oxidations reactions [15,18,20] and lead to mineralization of PHs to produce CO 2 and H 2 O [15,21]. Additionally, the microbial actions such as phosphorus solubilization, ACC-deaminase activity and siderophores production also improve the plants health in the PHs contamination [19,22,23].…”

“…Additionally, the microbial actions such as phosphorus solubilization, ACC-deaminase activity and siderophores production also improve the plants health in the PHs contamination [19,22,23]. In return, plant roots release massive amounts of hormones, vitamins, amino acids, organic acids, sugars, mucilage and other related compounds that encourage the microbial activities in the rhizosphere [20,22,24]. Many aromatic fractions of PHs have structural similarity with most of the root exudates, that is why microbial communities use them as a carbon source and increase their biomass coupled with PHs removal from the soil [25][26][27][28].…”