Isolation and characterization of phenol degrading bacterium strain Bacillus thuringiensis J20 from olive waste in Palestine

Gut microbiota metagenomics and mediation of phenol degradation in Bactrocera minax (Diptera, Tephritidae)

BACKGROUND

Gut microbiota mediating insect-plant interactions have many manifestations, either by provisioning missing nutrients, or by overcoming plant defensive reactions. However, the mechanism by which gut microbiota empower insects to survive by overcoming a variety of plant secondary metabolites remains largely unknown. Bactrocera minax larvae develop in immature citrus fruits, which present numerous phenolic compounds that challenge the larvae. To explore the role of gut microbes in host use and adaptability, we uncovered the mechanisms of phenol degradation by gut microbes using metagenomic and metatranscriptomic analyses, and verified the degradation ability of isolated and cultured bacteria. Research on this subject can help develop potential strain for the environmental friendly pest management operations.

RESULTS

We demonstrated the ability of gut microbes in B. minax larvae to degrade phenols in unripe citrus. After antibiotic treatment, coniferyl alcohol and coumaric aldehyde significantly reduced the survival rate, body length and body weight of the larvae. The metagenomic and metatranscriptomic analyses in B. minax provided evidence for the presence of genes in bacteria and the related pathway involved in phenol degradation. Among them, Enterococcus faecalis and Serratia marcescens, isolated from the gut of B. minax larvae, played critical roles in phenol degradation. Furthermore, supplementation of E. faecalis and S. marcescens in artificial diets containing coniferyl alcohol and coumaric aldehyde increased the survival rate of larvae.

CONCLUSION

In summary, our results provided the first comprehensive analysis of gut bacterial communities by high-throughput sequencing and elucidated the role of bacteria in phenol degradation in B. minax, which shed light on the mechanism underlying specialist insect adaption to host secondary metabolites via gut bacteria. © 2024 Society of Chemical Industry.

New roles for Bacillus thuringiensis in the removal of environmental pollutants

For a long time, the well-known Gram-positive bacterium Bacillus thuringiensis (Bt) has been extensively studied and developed as a biological insecticide for Lepidoptera and Coleoptera pests due to its ability to secrete a large number of specific insecticidal proteins. In recent years, studies have found that Bt strains can also potentially biodegrade residual pollutants in the environment. Many researchers have isolated Bt strains from multiple sites polluted by exogenous compounds and characterized and identified their xenobiotic-degrading potential. Furthermore, its pathway for degradation was also investigated at molecular level, and a number of major genes/enzymes responsible for degradation have been explored. At present, a variety of xenobiotics involved in degradation in Bt have been reported, including inorganic pollutants (used in the field of heavy metal biosorption and recovery and precious metal recovery and regeneration), pesticides (chlorpyrifos, cypermethrin, 2,2-dichloropropionic acid, etc.), organic tin, petroleum and polycyclic aromatic hydrocarbons, reactive dyes (congo red, methyl orange, methyl blue, etc.), and ibuprofen, among others. In this paper, the biodegrading ability of Bt is reviewed according to the categories of related pollutants, so as to emphasize that Bt is a powerful agent for removing environmental pollutants.

Biodegradation modeling of phenol using Curtobacterium flaccumfaciens as plant-growth-promoting bacteria

Phenol is a major worry pollutant resulting from industrialized manufacturing and chemical reactions. The growth kinetics and biodegradation of phenol were initially investigated using C. flaccumfaciens, a recently identified plant growth stimulating bacterium. Based on the Haldane inhibition model, Haldane's growth kinetics inhibition coefficient (Ki), half-saturation coefficient (Ks), and the maximum specific growth rate (max) for phenol-dependent growth kinetics were estimated to be 329 (mg/L), 9.14 (mg/L), and 1.05 (h⁻¹), respectively. With a sum of squared error (SSR) of 1.36 × 10⁻³, the Haldane equation is well adapted to empirical data. The improved Gombertz model also accurately predicts phenol biodegradation trends. The rate of phenol biodegradation and the lag time both increased as the initial phenol concentrations were increased. C. flaccumfaciens growth and phenol biodegradation were best achieved at a pH of 7.0 at a temperature of 28 °C incubation. A phenol biodegradation mechanism by C. flaccumfaciens has been proposed. In conclusion, this study revealed the ability of C. flaccumfaciens to promote plant growth and biodegrade phenol simultaneously. This could aid in rhizoremediation and crop yield preservation in phenol-stressed conditions.

Immobilization of Halomonas halodurans and Bacillus halodurans in packed bed bioreactor for continuous removal of phenolic impurities in waste water

Phenol is an organic contaminant widely distributed in wastewater. Biodegradation is one of the suitable methods used to remove phenol from the wastewater. In this study, the bacterial laccase and pectinase were analyzed and phenol degradation potential was studied. A total of six bacterial strains were selected and their phenol degrading potentials were studied. Laccase and pectinase producers were screened on substrate agar plates and several strains produced these enzymes in submerged fermentation. Among these enzyme producing strains, strain PD8 and PD22 exhibited potent phenol degrading ability than other strains. These two bacterial strains (Halomonas halodurans PD8 and Bacillus halodurans PD22) exhibited maximum growth in phenol-supplemented culture medium. These two organisms grown well at wide pH values (pH 3.0 and 10.0), survive well between 20 °C and 50 °C, and showed growth between 1 and 10% sodium chloride concentration. The lyophilized enzyme from PD8 and PD22 were immobilized with alginate beads cross liked with divalent cations. At 1% alginate, the binding efficiency was 40.2 ± 2.9% and it improved up to 2.0% concentration (67.5 ± 4.2%) and further increase on alginate concentration affected binding efficiency. Phenol degradation was maximum within 10 h of treatment in the immobilized packed bed column reactor (83.1 ± 3.2%) and colour removal efficiency was maximum at 12 h treatment (82.1 ± 3.9%). After four successive experimental trials more than 40% efficiency was achieved.

Phenol biodegradation by immobilized Rhodococcus qingshengii isolated from coking effluent on Na-alginate and magnetic chitosan-alginate nanocomposite

Phenol is a hazardous organic solvent to living organisms, even in its small amounts. In order to bioremediation of phenol from aqueous solution, a novel bacterial strain was isolated from coking wastewater, identified as Rhodococcus qingshengii based on 16S rRNA sequence analysis and named as strain Sahand110. The phenol-biodegrading capabilities of the free and immobilized cells of Sahand110 on the beads of Na-alginate (NA) and magnetic chitosan-alginate (MCA) nanocomposite were evaluated under different initial phenol concentrations (200, 400, 600, 800 and 1000 mg/L). Results illustrated that Sahand110 was able to grow and complete degrade phenol up to 600 mg/L, as the sole carbon and energy source. Immobilized cells of Sahand110 on NA and MCA were more competent than its free cells in degradation of high phenol concentrations, 100% of 1000 mg/L phenol within 96 h, indicating the improved tolerance and performance of the immobilized cells against phenol toxicity. Therefore, the immobilized Sahand110 on the studied beads, especially MCA bead regarding its suitable properties, has significant potential to enhanced bioremediation of phenol-rich wastewaters.

Linking Increased Isotope Fractionation at Low Concentrations to Enzyme Activity Regulation: 4-Cl Phenol Degradation by Arthrobacter chlorophenolicus A6

Slow microbial degradation of organic trace chemicals ("micropollutants") has been attributed to either downregulation of enzymatic turnover or rate-limiting substrate supply at low concentrations. In previous biodegradation studies, a drastic decrease in isotope fractionation of atrazine revealed a transition from rate-limiting enzyme turnover to membrane permeation as a bottleneck when concentrations fell below the Monod constant of microbial growth. With degradation of the pollutant 4-chlorophenol (4-CP) by Arthrobacter chlorophenolicus A6, this study targeted a bacterium which adapts its enzyme activity to concentrations. Unlike with atrazine degradation, isotope fractionation of 4-CP increased at lower concentrations, from ε(C) = -1.0 ± 0.5‰ in chemostats (D = 0.090 h^-1, 88 mg L^-1) and ε(C) = -2.1 ± 0.5‰ in batch (c₀ = 220 mg L^-1) to ε(C) = -4.1 ± 0.2‰ in chemostats at 90 μg L^-1. Surprisingly, fatty acid composition indicated increased cell wall permeability at high concentrations, while proteomics revealed that catabolic enzymes (CphCI and CphCII) were differentially expressed at D = 0.090 h^-1. These observations support regulation on the enzyme activity level─through either a metabolic shift between catabolic pathways or decreased enzymatic turnover at low concentrations─and, hence, reveal an alternative end-member scenario for bacterial adaptation at low concentrations. Including more degrader strains into this multidisciplinary analytical approach offers the perspective to build a knowledge base on bottlenecks of bioremediation at low concentrations that considers bacterial adaptation.

Phenol biodegradation by plant growth promoting bacterium, S. odorifera: kinetic modeling and process optimization

One of the main organic pollutants that could result from industrial products and chemical transformations is phenol. In the current study, the kinetics of Serratia odorifera, which was isolated from arable soil, was studied by growing it on broth minimal medium spiked with phenol as only carbon source and energy. The newly isolated plant growth-promoting bacterium (PGPB), S. odorifera, was used for the first time for phenol biodegradation. The growth kinetics parameters (phenol-dependent) including maximum specific growth rate (μmax), half-saturation coefficient (Ks), and the Haldane's growth kinetics inhibition coefficient (Ki), were tested via Haldane inhibition model and resulted on the 0.469 (h ^-1), 26.6 (mgL^-1), and 292 (mgL^-1), respectively. The sum of squared error (SSR) of 4.89 × 10^-3 was fitted to the experimental data by Haldane equation. The results of phenol biodegradation were fitted into the modified Gombertz model. The increase of phenol concentrations led to increases in both the rate of phenol biodegradation and lagging time. The optimal phenol biodegradation and bacterial growth obtained by S. odorifera, were at 28 °C incubation temperature and a pH of 7.0. The pathway of phenol biodegradation by S. odorifera was proposed in the current study to provide a new insight into synchronization of phenol biodegradation and plant growth-promoting bacteria. This may play an important role in remediation of phenol-contaminated soil besides promoting the plant growth, thus lessening the plant stress.

Synchronous degradation of phenol and aniline by Rhodococcus sp.strain PB-1entrapped in sodium alginate-bamboo charcoal-chitosan beads

The biodegradation of benzene series compounds is a difficult problem in environment pollution control, which is attributed to the deficiency of high efficiency bacteria and suitable embedding materials. In this study, the immobilized cells Rhodococcussp. strain PB-1 was used to synchronously biodegrade phenol and aniline by entrapped in sodium alginate (SA)-bamboo charcoal (BC)-chitosan acetate (CA) beads. The free cells of the strain PB-1 could completely degrade 1500 mg/L phenol or 800 mg/L aniline within 48 h, while the degradation rate of 2000 mg/L phenol and 1500 mg/L aniline was 35.76% and 68.06% at 72 h, respectively. The ortho-cleavage pathway was used to degrade phenol and aniline by strain PB-1. However, after entrapped with SA-BC-CA beads,the removal rate of 2000 mg/L phenol was 100% at 108 h, 1500 mg/L aniline was 100% at 62 h and 2000-3000 mg/L total toxic compounds was over 95% at 120 h. These beads could be used four times and were more effective than SA or SA-BC beads. The SA-BC-CA beads could remarkably improve the stability and degradation efficiency of strain PB-1, and thus provide a potential application in the removal of phenol and aniline in wastewater.

Bacterial consortium biotransformation of pentachlorophenol contaminated wastewater

The aims of this study were (i) to compare PCP removal (100 mg L^-1) by two bacterial consortia B₁ and B₂ in sterile wastewater (STWW) and liquid mineral medium (MSM), (ii) PCP effect in biofilm formation and antimicrobial susceptibility. PCP removal was measured by high-performance liquid chromatography (HPLC) during 168 h at 30 °C. Biofilm formation was assessed with two approaches: Congo Red Agar and Microtiter-plate. Antimicrobial susceptibility was determined by the agar disc diffusion technique. The results showed that the PCP removal for consortium B₁ and B₂ after 168 h was 70 and 97.5% in STWW; 62.2 and 85.5% in MSM, respectively. In addition, PCP addition showed an increase in biofilm development especially for B₂ consortium around 3.5 nm in 100 mg L^-1 PCP. PCP added in the Muller Hinton (MH) medium and Gentamicin disc showed a clear increase in diameter of cell lysis around 2 to 4.5 cm.

Bioremediation of Copper-Ions by Polymer Encapsulated and Immobilized Micrococcus Luteus

Bioremediation of copper (Cu²⁺ ) with immobilized Micrococcus luteus in polymer matrices has been broadly studied for a wide range of applications including wastewater treatment. Herein, the bioremediation efficiency based on modified immobilization techniques and by the addition of Cu²⁺ is investigated. Porous composite nonwovens with living M. luteus (living polymer composites) are prepared by encapsulation of the bacterial cells in poly(vinyl alcohol) (PVA) microparticles (M. luteus/PVA microparticles) produced by spray drying method. The M. luteus/PVA microparticles are chemically cross-linked. The hydrogel microparticles with encapsulated M. luteus are embedded in a nonwoven of poly (lactic acid) (PLA) electrospun short fibers provided by wet-laid method. Two different models of composite nonwovens are reported, in which the place position of the hydrogel PVA microparticles with encapsulated M. luteus and PLA nonwoven can affect the bioremediation process.

Survivability of Alcaligenaceae and Chromatiaceae as palm oil mill effluent pollution bioindicators under fluctuations of temperature, pH and total suspended solid

Alcaligenaceae and Chromatiaceae were previously reported as the specific pollution bioindicators in the receiving river water contaminated by palm oil mill effluent (POME) final discharge. Considering the inevitable sensitivity of bacteria under environmental stresses, it is crucial to assess the survivability of both bacteria in the fluctuated environmental factors, proving their credibility as POME pollution bioindicators in the environment. In this study, the survivability of Alcaligenaceae and Chromatiaceae from facultative pond, algae (aerobic) pond and final discharge were evaluated under varying sets of temperature (25-40°C), pH (pH 7-9) and low/high total suspended solid (TSS) contents of POME collected during low/high crop seasons of oil palm, respectively. Following treatment, the viability status and compositions of the bacterial community were assessed using flow cytometry-based assay and high-throughput Illumina MiSeq, respectively, in correlation with the changes of physicochemical properties. The changes in temperature, pH and TSS indeed changed the physicochemical properties of POME. The functionality of bacterial cells was also shifted where the viable cells and high nucleic acid contents reduced at elevated levels of temperature and pH but increased at high TSS content. Interestingly, the Alcaligenaceae and Chromatiaceae continuously detected in the samples which accounted for more than 0.5% of relative abundance, with a positive correlation with biological oxygen demand (BOD₅) concentration. Therefore, either Alcaligenaceae or Chromatiaceae or both could be regarded as the reliable and specific bacterial indicators to indicate the pollution in river water due to POME final discharge despite the fluctuations in temperature, pH and TSS.