Microorganism-assisted phytoremediation is being developed as an efficient green approach for management of toxic metals contaminated soils and mitigating the potential human health risk. The capability of plant growth promoting Actinobacteria (Streptomyces pactum Act12 - ACT) and Firmicutes (Bacillus subtilis and Bacillus licheniformis - BC) in mono- and co-applications (consortium) to improve soil properties and enhance phytoextraction of Cd, Cu, Pb, and Zn by Brassica juncea (L.) Czern. was studied here for the first time in both incubation and pot experiments. The predominant microbial taxa were Proteobacteria, Actinobacteria and Bacteroidetes, which are important lineages for maintaining soil ecological activities. The consortium improved the levels of alkaline phosphatase, β-D glucosidase, dehydrogenase, sucrase and urease (up to 33%) as compared to the control. The bacterial inoculum also triggered increases in plant fresh weight, pigments and antioxidants. The consortium application enhanced significantly the metals bioavailability (DTPA extractable) and mobilization (acid soluble fraction), relative to those in the unamended soil; therefore, significantly improved the metals uptake by roots and shoots. The phytoextraction indices indicated that B. juncea is an efficient accumulator of Cd and Zn. Overall, co-application of ACT and BC can be an effective solution for enhancing phytoremediation potential and thus reducing the potential human health risk from smelter-contaminated soil. Field studies may further credit the understanding of consortium interactions with soil and different plant systems in remediating multi-metal contaminated environments.

The Bacillus licheniformis strain YX2, a novel nitrobenzene-degrading halophilic bacterium, was isolated from active sludge obtained from a pesticide factory. Strain YX2 can withstand highly acidic and alkaline conditions and high temperatures. Degradation of nitrobenzene (200mgL−1) by YX2 exceeded 70% after 72h in lysogeny broth medium (pH 4–9). Under optimal degradation conditions (33°C, pH 7 in LB medium) YX2 degraded 50, 100, 200, and 600mgL−1 nitrobenzene within 36, 36, 72, and 156h, respectively. Even in the presence of benzene, phenol or aniline, strain YX2 efficiently degraded nitrobenzene. Furthermore, strain YX2 completely degraded 600mgL−1 nitrobenzene in 7% NaCl (w/w). Thus, our data show that strain YX2 may have promise for removing nitrobenzene from complex wastewaters with high salinity and variable pH.

Petroleum hydrocarbon pollution in marine waters has been an extremely significant environmental and health issue worldwide. This study aims at constructing an efficient indigenous bacterial consortium to biodegrade Tapis Light Crude Petroleum Oil (TLCO). The local agro-industrial wastewater of palm oil mill effluent final discharge (POME FD) was used as biostimulant to enhance the biodegradation efficiency. In this study, three TLCO degrading bacteria were isolated from seawater samples collected. Molecular identification using 16S rRNA genes sequencing was done and results show that these isolated strains belong to: Bacillus tropicus, Bacillus licheniformis and Bacillus subtilis. Bacterial consortium tested using four different concentrations of POME FD (0.1, 0.25, 0.5, and 1%) as biostimulant and TLCO (0.5 and 1.0%) degradation capability was investigated. The residual TLCO in culture medium after 40 days was analysed. The results confirmed that POME FD dosage of 0.25% is optimum for the bacterial consortium and can degrade 99.85% of TLCO at 0.5%. However, TLCO degradation with POME FD dosage (0.25%) in TLCO (1.0%) was found optimum, with biodegradation reaching up to 95.23% in 40 days. This study is a beginning for the future development of a consortium of petroleum hydrocarbon degrading bacteria to mitigate oil spills in the Malaysian shoreline.

In our previous research, a petroleum degrading bacteria strain Bacillus licheniformis Y-1 was obtained in Dagang Oilfield which had the capability of producing biosurfactant. This biosurfactant was isolated and purified in this work. The biosurfactant produced by strain Y-1 had the capability to decrease the surface tension of water from 74.66 to 27.26mN/m, with the critical micelle concentration (CMC) of 40mg/L. The biosurfactant performed not only excellent stabilities against pH, temperature and salinity, but also great emulsifying activities to different kinds of oil, especially the crude oil. According to the results of FT-IR spectrum and 1H NMR spectrum detection, the surfactant was determined to be a cyclic lipopeptide. Furthermore, through the addition of surfactant, the effect of petroleum contaminated soil remediation by fungi got a significant improvement.

In this work, a hydrocarbon-degrading bacterium Y-1 isolated from petroleum contaminated soil in the Dagang Oilfield was investigated for its potential effect in biodegradation of crude oil. According to the analysis of 16S rRNA sequences, strain Y-1 was identified as Bacillus licheniformis. The growth parameters such as pH, temperature, and salinity were optimised and 60.2% degradation of crude oil removal was observed in 5days. The strain Y-1 showed strong tolerance to high salinity, alkalinity, and temperature. Emplastic produced by strain Y-1 at high temperatures could be applied as biosurfactant. Gas chromatography analysis demonstrated that the strain Y-1 efficiently degraded different alkanes from crude oil, and the emplastic produced by strain Y-1 promoted the degradation rates of long-chain alkanes when the temperature increased to 55°C. Therefore, strain Y-1 would play an important role in the area of crude oil contaminant bioremediation even in some extreme conditions.

The production of a lipopeptide surfactant from the sponge-associated eubacteria Bacillus licheniformis NIOT-AMKV06 from the Andaman and Nicobar Islands was investigated. The highest production was attained with glucose and yeast extracts as the carbon and nitrogen sources (1.789mgmL−1), respectively. The surfactant was highly stable over a pH range of 5.0–10 and a temperature range of 20–70°C with high NaCl concentrations. Excellent emulsification activity was exhibited by the purified surfactant with crude oil, kerosene, and diesel. A two-fold increase in surfactant production (3.0mgmL−1) was observed using the newly formulated medium in this study. The surfactant biosynthesis gene cluster (sfp, sfpO, and srfA) from B. licheniformis NIOT-AMKV06 was heterologously expressed in Escherichia coli, and the production was increased three-fold (11.78gL−1) over the original strain. The results confirm the potential of the surfactant for use in bioremediation of hydrocarbons in a marine environment and for enhanced oil recovery. To our knowledge, this is the first report on the ability of a hydrocarbon to degrade B. licheniformis from marine sponges for the biosynthesis of a potent lipopeptide surfactant possessing characteristics of maximum stability, outstanding surfactant activity, and exceptional emulsifying capability.

The endophytic bacteria live in close nuptial relationship with the host plant. The stress experienced by the plant is expected to be transferred to the endophytes. Thus, plants thriving at polluted sites are likely to harbor pollutant-degrading endophytes. The present study reports the isolation of phenylurea herbicides assimilating Bacillus sps. from Parthenium weed growing at diuron-contaminated site. The isolated endophytes exhibited plant growth–promoting (PGP) activities. Among five isolated diuron-degrading endophytes, the most efficient isolate Bacillus licheniformis strain SDS12 degraded 85.60 ± 1.36% of 50 ppm diuron to benign form via formation of degradation intermediate 3, 4-dichloroaniline (3,4-DCA). Cell-free supernatant (CFS) obtained after diuron degradation by strain SDS12 supported algal growth comparable with the pond water. The chlorophyll content and photosynthetic efficiency of green algae decreased significantly in the presence of diuron-contaminated water; however, no such change was observed in CFS of strain SDS12, thus, suggesting that strain SDS12 can be applied in aquatic bodies for degrading diuron and reducing diuron toxicity for primary producers. Further, the use of PGP and diuron-degrading bacteria in agriculture fields will not only help in remediating the soil but also support plant growth.

This study compared the tolerance limits of selected bacterial (Bacillus licheniformis, Brevibacillus lactosporus and Pseudomonas putida) and protozoan (Aspidisca, Trachelophyllum and Peranema) species to V5+ in wastewater systems. The isolates were exposed to various concentrations of V5+ (from 10 to 240 ppm), and their tolerance limits to this heavy metal were assessed at different temperatures (25, 30, 35 and 40°C) and pHs (4, 6, 7, 8 and 10) for 5 days. Chemical oxygen demand (COD), dissolved oxygen (DO) and die-off rate of the isolates were measured using standard methods. The results indicated that test isolates were tolerant to V5+, with a gradual decrease in their colony/cell counts when V5+ concentration gradually increased. Bacterial species were found to be more significantly tolerant (MIC: 110–230 ppm V5+) to V5+ than protozoan species which showed an earlier total inhibition/die-off rate (100%) at 60–100 ppm V5+ (MIC) (p < 0.001). P. putida was the most tolerant bacterial species (MIC: 230 ppm V5+) and Aspidisca sp. the most sensitive protozoan species (MIC: 60 ppm V5+). An increase in COD and DO removal was observed throughout the experimental period. The highest COD increase (up to 237.11%) and DO removal (almost 100%) were observed in mixed liquor inoculated with P. putida after exposure to 10 ppm V5+. Changes in pH and temperature affected the tolerance limits of all isolates. This study suggests the use of these tolerant bacterial and protozoan species in the bioremediation of V5+ from domestic and industrial wastewater under the control of pH and temperature.

The chemical composition of root exudates and root extracts from Chrysopogon zizanioides (L.) Roberty cv KS-1 was determined in the presence of lead [Pb(II)]. Hitherto, no information is available in the literature concerning the phytochemical components of root exudates of C. zizanioides. Significantly higher concentrations of total carbohydrates (26.75 and 42.62% in root exudates and root extract, respectively), reducing sugars (21.46 and 56.11% in root exudates and root extract, respectively), total proteins (9.22 and 23.70% in root exudates and root extract, respectively), total phenolic acids (14.69 and 8.33% in root exudates and root extract, respectively), total flavonoids (14.30 and 12.28% in root exudates and root extract, respectively), and total alkaloids (12.48 and 7.96% in root exudates and root extract, respectively) were observed in samples from plants growing under Pb(II) stress in comparison to the respective controls. GC–MS profiling showed the presence of a diverse group of compounds in root exudates and extracts, including terpenes, alkaloids, flavonoids, carotenoids, plant hormones, carboxylic/organic acids, and fatty acids. Among the detected compounds, many have an important role in plant development, regulating rhizosphere microbiota and allelopathy. Furthermore, the results indicated that C. zizanioides exudates possess a chemotactic response for rhizospheric bacterial strains Bacillus licheniformis, Bacillus subtilis, and Acinetobacter junii Pb1.

Chlorella vulgaris and Bacillus licheniformis consortium was added to synthetic wastewater with exogenous vitamin B₁₂. In the presence of 100 ng/L vitamin B₁₂, removal efficiencies of TN, NH₃-N, PO₄³—P, and COD were 80.1%, 76.8%, 87.9%, and 76.7%, respectively. The functional groups on the cell surface of the consortium, including -NH, -CH₃, C=O, C=C, and P-O-C, increased with 100 ng/L vitamin B₁₂. These functional groups improved the biological adsorption of the consortium; however, higher concentrations of vitamin B₁₂ resulted in an occlusion of the functional groups. Furthermore, there were 5 significantly enriched protein pathways, namely carbon fixation in photosynthetic organisms; amino acid metabolic pathways; the pathway of one carbon pool by folate; nitrogen metabolism; and photosynthesis. Most proteins in these pathways were upregulated, which enhanced carbon fixation and photosynthesis in the algal cells. Simultaneously, B₁₂ promoted significant upregulation of proteins associated with the quorum-sensing pathway, which promoted the interaction between algae and bacteria.