Biodegradation of phenol and m-cresol in a batch and fed batch operated internal loop airlift bioreactor by indigenous mixed microbial culture predominantly Pseudomonas sp

Natural Source Zone Depletion (NSZD) Quantification Techniques: Innovations and Future Directions

Natural source zone depletion (NSZD) is an emerging technique for sustainable and cost-effective bioremediation of light non-aqueous phase liquid (LNAPL) in oil spill sites. Depending on regulatory objectives, NSZD has the potential to be used as either the primary or sole LNAPL management technique. To achieve this goal, NSZD rate (i.e., rate of bulk LNAPL mass depletion) should be quantified accurately and precisely. NSZD has certain characteristic features that have been used as surrogates to quantify the NSZD rates. This review highlights the most recent trends in technology development for NSZD data collection and rate estimation, with a focus on the operational and technical advantages and limitations of the associated techniques. So far, four principal techniques are developed, including concentration gradient (CG), dynamic closed chamber (DCC), CO2 trap and thermal monitoring. Discussions revolving around two techniques, “CO2 trap” and “thermal monitoring”, are expanded due to the particular attention to them in the current industry. The gaps of knowledge relevant to the NSZD monitoring techniques are identified and the issues which merit further research are outlined. It is hoped that this review can provide researchers and practitioners with sufficient information to opt the best practice for the research and application of NSZD for the management of LNAPL impacted sites.

Capacity of Marine Microalga Tetraselmis suecica to Biodegrade Phenols in Aqueous Media

Phenolic compounds are toxic and dangerous to the environment and human health. Although the removal of phenols and their derivatives is very difficult, it has been achieved by applying some biological processes. The capacity of microalga to remove phenolic compounds has been demonstrated; however, few reports of the removal of these compounds in a mixture have been published. The removal of phenol, p-cresol and o-cresol was performed by batch kinetics at 50 and 100 mg L−1, and the simultaneous degradation of phenol, p-cresol and o-cresol was carried out in a mixture at 40 mg L−1 using the marine microalga Tetraselmis suecica. The kinetic study was carried out for 192 h. For concentrations of 50 mg L−1 and 100 mg L−1, phenolic compound consumption efficiencies greater than 100% and 85%, respectively, were obtained, and up to 73.6% removal in the mixture. The results obtained indicate that the marine microalga carries out a process of the oxidation of organic matter and phenolic compounds, mineralizing up to 31.4% to CO2 in the mixture. Biological treatments using the marine microalga T. suecica can be considered feasible to treat effluents with concentrations similar to those of the present study.

Effectiveness of various bioreactors for thraustochytrid culture and production (Aurantiochytruim limacinum BUCHAXM 122)

This study aimed to develop bioreactors for cultivation of thraustochytrid, Aurantiochytrium limacinum BUCHAXM 122, that are low in cost and simple to operate. Obtaining maximum biomass and fatty acid production was a prerequisite. Three bioreactor designs were used: stirred tank bioreactor (STB), bubble bioreactor (BB) and internal loop airlift bioreactor (ILAB). The bioreactors were evaluated for their influence on oxygen mass transfer coefficient (k_La), using various spargers, mixing speed, and aeration rates. Biomass and DHA production from STB, BB, ILAB were then compared with an incubator shaker, using batch culture experiments. Results showed that a bundle of eight super-fine pore air stones was the best type of aeration sparger for all three bioreactors. Optimal culture conditions in STB were 600 rpm agitation speed and 2 vvm aeration rate, while 2 vvm and 1.5 vvm aeration provided highest biomass productivity in BB and ILAB, respectively. Antifoam agent was needed for all reactor types in order to reduce excessive foaming. Results indicated that with optimized conditions, these bioreactors are capable of thraustochytrid cultivation with a similar efficiency as cultivation using a rotary shaker. STB had the highest k_La and provided the highest biomass of 43.05 ± 0.35 g/L at 48 h. BB was simple in design, had low operating costs and was easy to build, but yielded the lowest biomass (27.50 ± 1.56 g/L). ILAB, on the other hand, had lower k_La than STB, but provided highest fatty acid productivity, of 35.36 ± 2.51% TFA.

Biodegradation Kinetic Studies of Phenol and p-Cresol in a Batch and Continuous Stirred-Tank Bioreactor with Pseudomonas putida ATCC 17484 Cells

The biodegradation of phenol, p-cresol, and phenol plus p-cresol mixtures was evaluated using Pseudomonas putida ATCC 17484 in aerobic batch reactors. Shake-flask experiments were performed separately using growth medium with initial nominal concentrations of phenol (50–600 mg L−1) and p-cresol (50–600 mg L−1) as well as phenol (50–600 mg L−1) plus p-cresol (50–600 mg L−1). The complete degradation of phenol and p-cresol was achieved within 48 h and 48–56 h, respectively, for all initial concentrations of phenol and p-cresol. The maximum cell growth rate using phenol (μmax,P = 0.45 h−1) was much faster than that using p-cresol (μmax,C = 0.185−1 h). The larger Ki value for phenol (310.5 mg L−1) revealed that the P. putida cells had a higher resistance to phenol inhibition compared with p-cresol (243.56 mg L−1). A mixture of phenol and p-cresol in batch experiments resulted in the complete removal of phenol within 52–56 h for initial phenol concentrations of 50–500 mg L−1. The time needed to remove p-cresol completely was 48–56 h for initial p-cresol concentrations of 50–500 mg L−1. In the continuous-flow immobilized cells reactor, the degradation efficiency for phenol and p-cresol was 97.6 and 89.1%, respectively, at a stable condition.

Characterization of cometabolic degradation of p-cresol with phenol as growth substrate by Chlorella vulgaris

To investigate the potential application of Chlorella vulgaris in the treatment of coal gasification wastewater, the characteristics of phenol and p-cresol cometabolism by Chlorella vulgaris were studied, including phenol degradation, ammonia nitrogen removal, antioxidant enzyme activities, and phenol hydroxylase activity. The results showed that the highest tolerable concentrations of phenol and p-cresol for Chlorella vulgaris were 800 and 400 mg/L, respectively. During cometabolism, phenol at low concentrations (100 mg/L) significantly promoted the degradation of p-cresol. Meanwhile, the removal efficiency of ammonia nitrogen was approximately 60% and was not affected by variations in phenol concentration. Furthermore, the cometabolism of phenol and p-cresol was enhanced by improvement of phenol hydroxylase activity of Chlorella vulgaris after the addition of NaHCO₃ as an exogenous nutrient. Therefore, Chlorella vulgaris has a great potential for the biochemical treatment of coal gasification wastewater.

Simultaneous Diesel and Oxygen Transfer Rate on the Production of an Oil-degrading Consortium in an Airlift Bioreactor: High-dispersed Phase Concentration

The aim of this study was to simultaneously evaluate diesel transfer rate (DTR) and oxygen transfer rate (OTR) on the production of an oil-degrading consortium in a three-phase airlift bioreactor (ALB) working at high hydrocarbon phase concentration with the purpose of determine whether the oxygen transfer rate is increased or diminished by an increase in the oil-phase concentration. Increase in hydrocarbon concentration allows an increase in DTR and a consequently higher DTR/OTR ratio thus avoiding hydrocarbon mass transfer limitations. This study demonstrates evidence that at high diesel concentrations, the main carbon fate is the production of biosurfactants.

Biodegradation effects of o-cresol by Pseudomonas monteilii SHY on mustard seed germination

Cresols are ubiquitous due to industrial production and natural presence. o-cresol (2-methyl phenol) is highly toxic to both fauna and flora. It has been included in the EPA list as one of the priority pollutants. The deleterious effects of pesticides, herbicides, and many other chemical compounds on seed germination are known. However, the effect of o-cresol on seed germination is not known. Therefore, it is of interest to study the effect of o-cresol on germination of 13 different vegetable crop seeds using standard Filter Paper Method. There is no effect on germination for brinjal, red chili, and (green gram, chickpea, cucumber, tomato, fenugreek, cowpea, Green pea, coriander, and spinach, seeds even at 1500 mg/l of o-cresol However, okra and mustard were found to be sensitive to ocresol. Germination of mustard under controlled concentration of o-cresol showed similar results by soil method. It was found that germination percentage and seedling vigour (Vigour Index) was reduced by o-cresol. The percent germination was reduced to 64 and 12 at 25 and 50 mg o-cresol/kg soil as against 100% in the case of untreated control. The vigour index was reduced to 160 and 10, respectively as against of 646 that for the control. The viability of seeds by 2,3,5 - tetrazolium trichloride (TTC) test showed that a considerable reduction was observed at 200mg/l o-cresol. Reduced protease and amylase activity in o-cresol shows inhibited mustard generation. However, mustard generation inhibition was restored by the bioremediation of o-cresol using Pseudomonas monteilii SHY. Thus, the biodegradation effects of o-cresol by Pseudomonas monteilii SHY on mustard seed germination are shown.

Ammonia and phenol removal in an internal-circulate sequencing batch airlift reactor

An internal-circulate sequencing batch airlift reactor (IC-SBAR) has been developed to evaluate the efficiency of phenol and ammonia removal in treating synthetic wastewater. This study examined the effect of operation cycle on this system. Results showed that above 97.0% removal efficiencies of ammonia and phenol were achieved, which indicated that ammonia and phenol removals were not related to operation cycle. The average removal efficiency of 91.7% for chemical oxygen demand (COD) was achieved when the static/aerobic/settling time was 240 min/440 min/40 min. It was found that COD removal efficiency increased due to the time of operation cycle being prolonged. The average removal efficiencies of total inorganic nitrogen (TIN) were 65.8, 69.3 and 68.9% when average TIN concentrations were 78.0, 97.6 and 88.4 mg/L, respectively, in the influent. A cycle study showed that most phenol was degraded by aerobic microbes. Increasing the static time from 120 to 240 min resulted in the accumulation of NO2(-)-N, which indicated that the structures of the nitrifying bacterial community were changed.

Phenol biodegradation by different mixed cultures and the optimization of efficiency of the degradation

In this study, the phenol degradation capacities of four different mixed cultures, namely, Ankara Stream (AS), petroleum-contaminated soil (PS), olive mill wastewater (OMW), and drug mill wastewater (DMW) were investigated with regards to different pH levels, phenol (497.2-1183.0 mg/L) and biomass concentrations (0.5-3.0%(v/v)). The most efficient culture was selected and the optimal conditions required for its highest performance in phenol degradation were studied. We found 100% phenol degradation for DMW at nearly 1000 mg/L initial concentration. The optimum pH was 8 and the mixed culture could tolerate phenol levels up to approximately 1500 mg/L. The selected culture degraded all of the phenol concentrations ranging from 497.2 to 1183.0 mg/L with 100% efficiency after 48 h and 120 h incubation, respectively. Increasing the biomass concentration from 0.5% to 3.0% (v/v) level decreased the incubation time needed for complete degradation. The data indicate that the mixed culture used in this study can be taken as a good candidate for effective treatment of waters contaminated by phenol.

Electrochemical degradation of m-cresol using porous carbon-nanotube-containing cathode and Ti/SnO2-Sb2O5-IrO2 anode: kinetics, byproducts and biodegradability

The degradation of m-cresol solution was studied using an electrochemical oxidation system with Ti/SnO2-Sb2O5-IrO2 anode for anodic oxidation and porous carbon-nanotube-containing cathode for H2O2 electrogeneration along with Fe(3+) reduction. Organic pollutants were oxidized by hydroxyl radical (OH) formed simultaneously in the medium from electro-Fenton reaction in the presence of Fe(2+) and at the anode surface from water oxidation. The porous cathode made of graphite, carbon nanotube (CNT) and polytetrafluoroethene (PTFE) exhibited a higher catalytic activity toward O2 reduction producing H2O2 and Fe(3+) reduction for Fe(2+) regeneration, favoring organics degradation by electro-Fenton oxidation. The degradation kinetics results revealed that the reaction of m-cresol cleavage with hydroxyl radicals could be described by pseudo first-order kinetics. The progress of organics mineralization demonstrated some byproducts were formed during m-cresol degradation. Based on the byproducts identified by GC-MS and HPLC, the sequential process of m-cresol degradation was proposed. Furthermore, the aerobic biological treatment showed that the electrochemical treatment was able to evidently enhance the biodegradability of m-cresol solution.

Degradation of dimethyl-sulfoxide-containing wastewater using airlift bioreactor by polyvinyl-alcohol-immobilized cell beads

Airlift bioreactor containing polyvinyl-alcohol-immobilized cell beads was investigated for its capability of biodegradation of dimethyl sulfoxide (DMSO) in term of sludge characteristics including the strategy of acclimation with sucrose and the protection of microorganism from poisoning of DMSO by PVA cell beads. Media condition with sucrose at 50 mg L(-1) was beneficial to the biodegradation of DMSO in the fresh PVA entrapped-sludge, but became insignificant in the acclimated one as for tolerance of DMSO toxicity. The removal efficiency of DMSO had the highest rate at 1.42-kg DMSO per kilogram of suspended solid per day after series acclimation batches in the oxygen-enriched airlift bioreactor treated with the 1187.4 mg L(-1) of DMSO. Microbial consortium was required for the complete biodegradation of DMSO without any dimethyl sulfide produced. Pseudomonas sp. W1, excreting extracellular monooxygenase identified by indole, was isolated to be one of the most effective DMSO-degrading microorganism in our airlift bioreactor.

Proteomic insight into phenolic adaptation of a moderately halophilicHalomonassp. strain AAD12

A gram-negative, moderately halophilic bacterium was isolated from Çamaltı Saltern area, located in the Aegean Region of Turkey. Analysis of its 16S rRNA gene sequence and physiological characteristics showed that this strain belonged to the genus Halomonas ; hence, it was designated as Halomonas sp. strain AAD12. The isolate tolerated up to 800 mg⋅L–1phenol; however, at elevated concentrations, phenol severely retarded cell growth. The increase in lag phase with increasing phenol concentrations indicated that the microorganism was undergoing serious adaptative changes. To understand the physiological responses of Halomonas sp. strain AAD12 to phenol, a 2-dimensional electrophoresis approach combined with mass spectrometric analysis was used. This approach showed that the expression of 14 protein spots were altered as phenol concentration increased from 200 to 800 mg⋅L–1. Among the identified proteins were those involved in protein biosynthesis, energy, transport, and stress metabolism. So far, this is the first study on phenolic adaptation of a gram-negative, moderately halophilic bacteria using proteomic tools. The results provided new insights for understanding the general mechanism used by moderately halophilic bacteria to tolerate phenol and suggested the potential for using these microorganisms in bioremediation.

Dual substrates biodegradation kinetics of m-cresol and pyridine by Lysinibacillus cresolivorans

Phenols and N-heterocyclic compounds are found to co-exist in actual wastewater, especially in petrochemical and coking wastewater. Lysinibacillus cresolivorans, a bacterium capable of phenol-biodegradation was used to study the substrate interactions of m-cresol and pyridine as single and dual substrates. The cell growth and substrate biodegradation kinetics were also investigated with initial m-cresol concentrations varying from 0 to 1200 mg/L and pyridine concentrations varying from 0 to 150 mg/L. The single substrate kinetics was well described by the Haldane kinetic models. The single-substrate parameter values of m-cresol on cell growth were μ(max)=0.89 h(-1), K(s)=426.25 mg/L, K(i)=51.26 mg/L and μ(max)=0.0925 h(-1), K(s)=60.28 mg/L, K(i)=16.17 mg/L for cell growth on pyridine. Inhibitory effects of substrates were observed when cells were grown on the mixed substrates. The interaction parameter I(m,p) (0.76) was greater than I(m,p) (0.11), which indicated that m-cresol inhibited the utilization of pyridine much more than pyridine inhibited the biodegradation of m-cresol. The study showed a good potential of L. cresolivorans in degrading mixed substrates of m-cresol and pyridine.

Optimization of phenol degradation by Candida tropicalis Z-04 using Plackett-Burman design and response surface methodology

Statistical experimental designs were used to optimize the process of phenol degradation by Candida tropicalis Z-04, isolated from phenol-degrading aerobic granules. The most important factors influencing phenol degradation (p < 0.05), as identified by a two-level Plackett-Burman design with 11 variables, were yeast extract, phenol, inoculum size, and temperature. Steepest ascent method was undertaken to determine the optimal regions of these four significant factors. Central composite design (CCD) and response surface analysis were adopted to further investigate the mutual interactions between these variables and to identify their optimal values that would generate maximum phenol degradation. The analysis results indicated that interactions between yeast extract and temperature, phenol and temperature, inoculum size and temperature affected the response variable (phenol degradation) significantly. The predicted results showed that the maximum removal efficiency of phenol (99.10%) could be obtained under the optimum conditions of yeast extract 0.41 g/L, phenol 1.03 g/L, inoculum size 1.43% (V/V) and temperature 30.04 degrees C. These predicted values were further verified by validation experiments. The excellent correlation between predicted and experimental values confirmed the validity and practicability of this statistical optimum strategy. This study indicated the excellent ability of C. tropicalis Z-04 in degrading high-strength phenol. Optimal conditions obtained in this experiment laid a solid foundation for further use of this microorganism in the treatment of high-strength phenol effluents.

Functional consortia for cresol-degrading activated sludges: toxicity-to-extinction approach

The conventional roll tube and plating techniques are typically time consuming and can culture in vitro only a small fraction of microbes in natural microflora. This study utilizes a novel, simple, and rapid method, the toxicity-to-extinction approach, to obtain the minimal functional consortium that can effectively degrade meta- (m-), para- (p-), and ortho- (o-) cresols. The original sludge had 16 major bands by denaturing gradient gel electrophoresis (DGGE). Microbial diversity decreased as the cresol concentration increased. The functional strains acquired under toxic stress by dosed cresols that individually degraded m-, p-, and o-cresols were identified. Catechol 1,2-dioxygenase (C12D) and catechol 2,3-dioxygenase (C23D) activities in cell-free extracts were determined spectrophotometrically and were correlated with noted changes in microbial communities under cresol stress. The proposed toxicity-to-extinction approach is feasible for isolating a functional consortium from sludge for cresol degradation.

Biodegradation of phenol and m-cresol by mutated Candida tropicalis

The phenol and m-cresol biodegradations were studied using the mutant strain CTM 2 obtained by the He-Ne laser irradiation on wild-type Candida tropicalis. The results showed that C. tropicalis exhibited the increased capacity of phenolic compounds degradation after laser irradiation. It could degrade 2600 mg/L phenol and 300 mg/L m-cresol by 5% inoculum concentration, respectively. In the dual-substrate biodegradation system, 0-500 mg/L phenol could accelerate m-cresol biodegradation, and 300 mg/L m-cresol could be completely utilized within 46 hr at the presence of 350 mg/L phenol. Besides, the maximum biodegradation of m-cresol could reach 350 mg/L with 80 mg/L phenol within 61 hr. Obviously, phenol, as a growth substrate, could promote CTM 2 to degrade m-cresol, and was always preferentially utilized as carbon source. Comparatively, low-concentration m-cresol could result in a great inhibition on phenol degradation. In addition, the kinetic behaviors of cell growth and substrate biodegradation were described by kinetic model proposed in our laboratory.

Biodegradation of phenol using Corynebacterium sp. DJ1 aerobic granules

The single-culture Corynebacterium sp. DJ1 aerobic granules were cultivated and were utilized to degrade high-strength phenolic wastewater. These granules can degrade phenol at sufficient high rate without severe inhibitory effects up to phenol concentration of 2000 mg l(-1). Furthermore, the kinetic characteristic noted for these granules yields a zero-order phenol degradation behavior with 500-1500 mg l(-1) phenol, which facilitates reactor design and scale up. With added acetate to promote cell growth, this single-culture aerobic granular system yields the highest phenol degradation rate reported in granular literature.

Treatment of phenolics containing synthetic wastewater in an internal loop airlift bioreactor (ILALR) using indigenous mixed strain of Pseudomonas sp. under continuous mode of operation

The scope of this study is to evaluate the performance of internal loop airlift bioreactor (ILALR) in treating synthetic wastewater containing phenol and m-cresol, in single and multi component systems. The microbe utilized in the process was an indigenous mixed strain of Pseudomonas sp. isolated from a wastewater treatment plant. The reactor was operated at both lower and higher hydraulic retention times (HRTs) i.e., 4.1 and 8.3 h, respectively, by providing an inlet feed flow rate of 5 and 10 mL/min. Shock loading experiments were also performed up to a maximum concentration of 800 mg/L for phenol at 8.3 h HRT and 500 mg/L for m-cresol at 4.1 h HRT. The study showed complete degradation of both phenol and m-cresol, when they were degraded individually at a HRT of 8.3 h. Experiments with both phenol and m-cresol present as mixtures were performed based on the 2(2) full factorial design of experiments.