Coal Biodegradation Research Articles

Investigating functional mechanisms in the Co-biodegradation of lignite and guar gum under the influence of salinity

The biodegradation of guar gum by microorganisms sourced from coalbeds can result in low-temperature gel breaking, thereby reducing reservoir damage. However, limited attention has been given to the influence of salinity on the synergistic biodegradation of coal and guar gum. In this study, biodegradation experiments of guar gum and lignite were conducted under varying salinity conditions. The primary objective was to investigate the controlling effects and mechanisms of salinity on the synergistic biodegradation of lignite and guar gum. The findings revealed that salinity had an inhibitory effect on the biomethane production from the co-degradation of lignite and guar gum. The biomethane production declined with increasing salinity levels, decreasing from 120.9 mL to 47.3 mL. Even under 20 g/L salt stress conditions, bacteria in coalbeds could effectively break the gel and the viscosity decreased to levels below 5 mPa s. As salinity increased, the removal rate of soluble chemical oxygen demand (SCOD) decreased from 55.63% to 31.17%, and volatile fatty acids (VFAs) accumulated in the digestion system. High salt environment reduces the intensity of each fluorescence peak. Alterations in salinity led to changes in microbial community structure and diversity. Under salt stress, there was an increased relative abundance of Proteiniphilum and Methanobacterium, ensuring the continuity of anaerobic digestion. Hydrogentrophic methanogens exhibited higher salt tolerance compared to acetoclastic methanogens. These findings provide experimental evidence supporting the use of guar gum fracturing fluid in coalbeds with varying salinity levels.

Biodegradations of three different rank coals by a newly isolated bacterium Bacillus sp. XK1

Biodegradation of coal was closely related to coal rank. In this study, three kinds of coals whose coal ranks from high to low were Zhundong coal (ZDC), Hongshaquan coal (HSQC) and Heishan coal (HSC) were degraded by Bacillus sp. XK1 isolated from mine water. The degradation experiment results indicated that the degradation rate increased with the decrease of coal rank, and the highest degradation rate of HSC (low-rank coal) was 78.2 %, which was three times higher than that of ZDC (high-rank coal). The enzyme activity experiment showed that the alkaline protease and lignin peroxidase secreted by Bacillus sp. XK1 were key substances for coal biodegradation, and the alkaline protease activity and lignin peroxidase activity were all the highest in the presence of HSC, which were beneficial for coal biodegradation. The adsorption experiment found that HSC was more favorable to contact with Bacillus sp. XK1 than ZDC and HSQC. Furthermore, biodegradation products analysis suggested that with the decrease of coal rank, the contents of long chain alkanes in liquid products increased, among which the highest content of long chain alkane in liquid product of HSC was 86.98 %. The above experimental results demonstrated that biodegradation of low rank coal was an effective pathway.

Microbial Conversion of Sulfur-Containing Compounds Contributed the Natural Biodegradation of Bituminous Coals

Microorganisms can affect coal biodegradation by driving elemental biogeochemical cycling. A detailed description of the sulfur conversion process led by indigenous bacteria during coal degradation is important. This study obtained sulfur-containing compounds conversion bacteria through indoor enrichment and conducted anaerobic culture experiments using coal supplemented with enriched bacteria. The study showed that the addition of enriched bacteria changed the microbial composition, particularly the microbial groups within Pseudomonadota and Bacillota. In addition, the sulfur-containing compounds conversion bacteria increased the pore volume and specific surface area of micropores (<10 nm) and transition pores (10–100 nm), as well changed the content of sulfur-containing organic components including polypeptides, aromatic compounds, alkyl compounds, and thiazoles. The genera related to inorganic sulfur conversion were mainly belonging to Bacillota and Actinomycetota. Additionally, functional genera that can degrade sulfur-containing organic compounds of dibenzothiophenes through the ring-opening of benzene rings were found within Pseudomonadota, Bacillota and Actinomycetota. In summary, organic sulfur-related Pseudomonadota, Bacillota and Actinomycetota and inorganic sulfur-related Bacillota and Actinomycetota detected in this study could accelerate the sulfur-containing compounds conversion and ultimately increase micropores in coal, and this holds great significance for understanding the biogeochemical cycling process of coal.

Evidence of Coal Biodegradation from Coalbed-Produced Water - A Case Study of Dafosi Gas Field, Ordos Basin, China.

Bioconversion of coal to methane occurs in the coalbed aquifer environment. To investigate the evidence of coal biodegradation from coalbed-produced water, we collected six field water samples from the Dafosi gas field and prepared one laboratory-simulated water sample and one indoor anaerobic microbial degradation sample with the highest compound concentration as the two reference standards. Gas chromatography-mass spectrometry was used to detect the organic compound type, concentration, and differences in the biomarker compound sensitivity. Results indicate that extracted organic matter from coalbed-produced water samples can be evidence of biodegradation. Variations in range compounds (such as n-alkanes, tri- and pentacyclic terpenes, and steranes) and their sensitivity confirmed active microbial degradation in the studied area. A positive correlation between the n-alkanes content in the coalbed-produced water and the stable carbon isotope value of methane further verifies that the n-alkanes are primary substrates for maintaining microbial activity. Therefore, evidence including n-alkanes, tri- and pentacyclic terpenes, steranes, unresolved complex mixtures, and stable carbon isotope composition of methane contribute to biogenic methane generation in situ. Our limited data suggest that managing soluble organic matter in the coalbed-produced water may provide a viable route for coal biodegradation since most microorganisms survive within the coal seam water.

Influences of Four Kinds of Surfactants on Biodegradations of Tar-Rich Coal in the Ordos Basin by Bacillus bicheniformis.

The biodegradation of tar-rich coal in the Ordos Basin was carried out by Bacillus licheniformis (B. licheniformis) under actions of four kinds of surfactants, namely, a biological surfactant (Rh), a nonionic surfactant (Triton X-100), an anionic surfactant (LAS), and a cationic surfactant (DTAB). The biodegradation rates under the actions of Triton X-100, LAS, Rh, DTAB, and the control group (without surfactant) were 59.8%, 54.3%, 51.6%, 17.3%, and 43.5%, respectively. The biodegradation mechanism was studied by examining the influences of surfactants on coal samples, bacteria, and degradation products in the degradation process. The results demonstrated that Rh, Triton X-100, and LAS could promote bacterial growth, while DTAB had the opposite effect. Four surfactants all increased the cell surface hydrophobicity (CSH) of B. licheniformis, and Triton X-100 demonstrated the most significant promotion of CSH. The order of improvement in microbial cell permeability by surfactants was DTAB > TritonX-100 > LAS > Rh > control group. In the presence of four surfactants, Triton X-100 exhibited the best hydrophilicity improvement for oxidized coal. Overall, among the four surfactants, Triton X-100 ranked first in enhancing the CSH of bacteria and the hydrophilicity of oxidized coal and second in improving microbial cell permeability; thus, Triton X-100 was the most suitable surfactant for promoting B. licheniformis's biodegradation of tar-rich coal. The GC-MS showed that, after the action of Triton X-100, the amount of the identified degradation compounds in the toluene extract of the liquid product decreased by 16 compared to the control group, the amount of dichloromethane extract decreased by 6, and the amount of ethyl acetate extract increased by 6. Simultaneously, the contents of alkanes in the extracts of toluene and dichloromethane decreased, lipids increased, and ethyl acetate extract exhibited little change. The FTIR analysis of the coal sample suggested that, under the action of Triton X-100, compared to oxidized coal, the Har/H and A(CH2)/A(CH3) of the remaining coal decreased by 0.07 and 1.38, respectively, indicating that Triton X-100 enhanced the degradation of aromatic and aliphatic structures of oxidized coal. Therefore, adding a suitable surfactant can promote the biodegradation of tar-rich coal and enrich its degradation product.

The effect of organics transformation and migration on pore structure of bituminous coal and lignite during biomethane production.

Biomethane generation by coal degradation not only can increase coalbed methane (CBM) reserves, namely, microbially enhanced coalbed methane (MECBM), but also has a significant effect on the pore structure of coal which is the key factor in CBM extraction. The transformation and migration of organics in coal are essential to pore development under the action of microorganisms. Here, the biodegradation of bituminous coal and lignite to produce methane and the cultivation with inhibition of methanogenic activity by 2-bromoethanesulfonate (BES) were performed to analyze the effect of biodegradation on coal pore development by determining the changes of the pore structure and the organics in culture solution and coal. The results showed that the maximum methane productions from bituminous coal and lignite were 117.69μmol/g and 166.55μmol/g, respectively. Biodegradation mainly affected the development of micropore whose specific surface area (SSA) and pore volume (PV) decreased while the fractal dimension increased. After biodegradation, various organics were generated which were partly released into culture solution while a large number of them remained in residual coal. The content of newly generated heterocyclic organics and oxygen-containing aromatics in bituminous coal was 11.21% and 20.21%. And the content of heterocyclic organics in bituminous coal was negatively correlated with SSA and PV but positively correlated with the fractal dimension which suggested that the retention of organics contributed greatly to the decrease of pore development. But the retention effect on pore structure was relatively poor in lignite. Besides, microorganisms were observed around fissures in both coal samples after biodegradation which would not be conducive to the porosity of coal on the micron scale. These results revealed that the effect of biodegradation on pore development of coal was governed by the combined action of organics degradation to produce methane and organics retention in coal whose contributions were antagonistic and determined by coal rank and pore aperture. The better development of MECBM needs to enhance organics biodegradation and reduce organics retention in coal.

Insights into the response mechanism of Fusarium sp. NF01 during lignite biodegradation using proteomic analysis

Coal biodegradation is promising for sustainable energy development. Studying proteomics in coal biodegradation is effective for identifying different proteins and analyzing corresponding biological strategies. However, previous research on this topic is limited. Here, Fusarium sp. NF01 was proven to degrade lignite based on surface morphology, functional groups, and chemical composition for the first time. The proteomics of Fusarium sp. NF01 were then quantitatively and qualitatively analyzed using isobaric tandem mass tags and bioinformatics profiling during lignite biodegradation. The results showed that 1.8 g of lignite was biodegraded into 4.7 mL of black droplets, with microstructural changes. The abundance of 18 proteins, including eight upregulated and ten downregulated proteins (fold change, FC ≥ 1.2 or FC ≤ 0.83 and P-value ≤0.05), significantly changed during the lignite biodegradation process. These proteins were mainly involved in spermidine synthase, PM H+-ATPase, GGT, 6-HDNO, IPS, and AST. Fusarium sp. NF01 adopted multilevel protein-based strategies, such as nutrient transport and synthesis, positive plasma membrane regulation, immunity optimization, and prevention of cell damage and death to respond to the influence of the lignite environment on its growth and metabolism. These findings provide valuable bioinformation for identifying degradation-specific protein molecules and elucidating the biodegradation mechanism of coal.

Biogas production characteristics of lignite and related metabolic functions with indigenous microbes from different coal seams

To investigate the effects of different exogenous microorganisms on coal biomethanation and its related microbial metabolic functions. Bacterial sources were obtained from the mine water of the Xinsheng, Qinan, Fangzhuang, and Tianyuan coal mines, and lignite was utilized for conducting experiments to produce biomethane. The biomethane yield and statistical analysis based on KEGG metabolic pathways were used to assess the biomethane production potential and the difference of metabolic functions during anaerobic fermentation. The results showed that the accumulative production of biomethane in the anaerobic fermentation system with microorganisms from Qinan mine was 1.80 times, 1.18 times and 1.13 times that of the fermentation systems with other microbes from the Xinsheng, Fangzhuang and Tianyuan mine, respectively. Based on the geological environment of groundwater, it was observed that the moderate water-rich fractures in the coal seam fractures of Qinan Mine are relatively developed, which facilitates the transport of organic matter during microbial metabolism. On the other hand, the Fangzhuang and Tianyuan coal mines are situated in the groundwater runoff zone, their fracture development characteristics are comparatively lower than those of the Qinan mine. In contrast, the coal seam roof and floor of Xinsheng mine are characterized by a stable aquifer comprising thick mudstone and claystone, which presents difficulties for hydrogen-producing bacteria and methanogenic bacteria in obtaining liquid nutrients. This leads to a lower potential for methane production in the Xinsheng mine as compared to the other coal mines. The prediction based on 16S rRNA gene function showed that the microorganisms in Qinan mine had the largest abundance of annotated homologous genes involved in glycolysis, fatty acid synthesis, and methane metabolism, which had a significant positive correlation with methane production. An important observation was the absence of acetate-CoA ligase in the glycolytic pathway, which rules out the acetate-trophic pathway as a significant contributor to coal biodegradation and methanogenesis. Moreover, the abundance of genes related to the hydrogenotrophic methanogenesis pathway was found to be the highest during methane metabolism, indicating that the CO2 reduction pathway plays a significant role during the anaerobic fermentation of coal to produce biomethane.

Biogenic methane production from lignite in cube: Comparison of the inner and outer part of coal

The methane generation by coal biodegradation has been widely demonstrated in the laboratory. However, powder coal was mostly employed, and little is known about the methane production from coal in cube. A 2L fermenter was used here to perform the anaerobic degradation of lignite in cube by a fungi-methanogens mixed microflora. The results showed that the methane production reached 6578.51 μmol. After degradation, the contents of carbon, oxygen, hydrogen, and aromatic functional groups decreased in the inner part of residual coal (Inc) and reduced more in the outer part (ExC), suggesting that microorganisms can act inside the coal matrix although the action weakens. The specific surface area (SSA) and pore volume (PV) decreased in Inc but Increased in ExC due to the antagonistic effect of biodegradation and the retention of organics and microorganisms. Fermentative fungi and Methanosarcina dominated in fermentation broth where acids, especially fatty acids were the main intermediates. The results revealed that methane generation by biodegradation also happened inside coal matrix, laying a fundamental basis for the application of microbially enhanced coalbed methane. And further efforts are needed to enhance biodegradation to improve methane production and pore development.

Additions of esterase and rhamnolipid promote the degradation of Inner Mongolia coal by Pseudomonas japonica

The biodegradation of Inner Mongolia coal by Pseudomonas japonica (P. japonica) was investigated, showing that the biodegradability of P. japonica was related to its secretions: esterase (Es) and rhamnolipid (Rh). Therefore, the efficiencies of coal biodegradation were explored through additions of Es, Rh and the mixture of Es and Rh (Es-Rh) to the biodegradation system, respectively. It was found that the coal biodegradation rate all increased in the presence of Es-Rh, Es or Rh, among which Es-Rh significantly increased the coal biodegradation rate. When the ratio of Es-Rh was 150 mg/mL:1200 mg/mL, the coal biodegradation rate reached a maximum of 65.3% higher than the control group 18.8%, it was because the optical density and esterase activity of P. japonica were the highest, while the electronegativity and adsorption rate of coal samples were the optima. GC–MS of the degradation liquid products showed that the compositions of degradation liquid products in the presence of Es-Rh mainly contained long-chain alkanes, alcohols and ethers, of which the highest content of long-chain alkanes was 81.13%. FTIR analysis confirmed that the CH, CC and -COOR groups in Inner Mongolia coal were degraded in the presence of Es-Rh. XRD analysis demonstrated that the Lc and Nave decreased in the presence of Es-Rh, indicating that the crystallization degree of Inner Mongolia coal decreased. This study indicated that the addition of mixture of Es and Rh could significantly promote the degradation of Inner Mongolia coal by P. japonica.

Optimization of weathered coal biodegradation by Penicillium aculeatum 13-2-1 and UV-visible spectral characteristics of active degraded products

Weathered coal is widely distributed in many provinces in China. It has great potential utilization values as soil ameliorant in sustainable agriculture. To find the optimal condition for the biodegradation of weathered coal and obtain the spectral characteristics of active degraded products of coal, the bioactivation of humic acid in weathered coal is essential. In this study, a fungal strain (Penicillium aculeatum 13-2-1) capable of degrading weathered coal was isolated from the rhizosphere of Zelkova serrata. The experimental results using classical one factor at a time method showed that weathered coal of 1.0 g, inoculum of 150 µL, and sodium nitrate of 0.10 g in 100 mL broth were the optimal conditions for the biodegradation of coal, respectively. The variance analysis of orthogonal tests illustrated that the three factors had little effects on biodegradation of weathered coal, but the weathered coal significantly negatively affected the contents of soluble humic acids in liquid coal products. Different diluted solutions of liquid coal products for all orthogonal combinations promoted the growth of the seeds of Brassica napus L., especially on radicles. The UV-visible spectra of the liquid coal products for all combinations presented the differential absorbance closely associated with the quantity of sodium nitrate in medium.

Enhancements of mixed surfactants on Wucaiwan coal biodegradation by Nocardia mangyaensis

The use of surfactant to enhance the efficiency of coal biodegradation is a promising technology. In this paper, the effects of nonionic-anionic mixed surfactants TR-LAS and TW-LAS on Wucaiwan coal degradation by Nocardia mangyaensis (N. mangyaensis) were investigated, in which TR (octyl phenoxy poly ethoxy) and TW (polysorbate) were nonionic surfactants, and LAS (sodium dodecyl benzene sulfonate) was anionic surfactant. The results demonstrated the enhancement order of surfactant was TR-LAS > TW-LAS > TR > TW > LAS, and when the total mass of TR-LAS was 1000 mg/L and its ratio was 1200:800 (m/m), and the maximum biodegradation rate of Wucaiwan coal was 74.8% which increased by 23.6% than the control group (without surfactant). It was also found that nonionic surfactant TR was more effective than TW and LAS in promoting the growth of N. mangyaensis, meanwhile anionic surfactant LAS was more effective than TR and TW in increase the zeta potential of oxidized coal. The increase of bacterial growth will secrete more coal-degrading alkaline protease, and the increase of coal zata potential will make bacteria and coal contact easier, both of the above actions are conducive to biodegradation of coal. Thus, the mixed surfactants TR-LAS (1000 mg/L) achieved the strongest synergistic effect of nonionic and anionic surfactants, greatly promoting the biodegradation of coal. This study provides valuable information in designing the mixed surfactant to improve the efficiency of coal biodegradation process.

The variation of microorganisms and organics during methane production from lignite under an electric field.

The succession of microbial communities and intermediates during methane production was determined by pyrosequencing and GC-MS to investigate the mechanism of biomethanation enhancement from coal. The maximum methane production at 1.2V was significantly higher than that at 0V. Bacterial flora have been changed as a result of the addition of an electric field, e.g., the abundance of Pseudomonas significantly increased to enhance the coal degradation which improved the methane yield by facilitating the electron transfer. The fungal structure was also found stabilized by the electric field when compared to the control after 7days of cultivation. The predominance of Methanosarcina could also stimulate interspecies electron transfer. The GC-MS analysis revealed that the electric field can selectively promote the metabolism of refractory intermediates such as esters and aromatics during coal biodegradation. The application of an electric field could enhance methane production from coal by changing the structure and succession of microbial communities, improving electron transfer, and enhancing the fermentation of intermediates during coal biodegradation.

Clean utilization of lignite to produce biomethane by optimizing the microbial community

Optimization of microbial community is requisite to boost methane production from inferior coal biodegradation. Here is reported an efficient method of converting lignite into methane by microorganisms, which takes lignite as substrate and obtains efficient microbial flora from sludge by means of enrichment and domestication. The Single Factor Experiment and Response Surface Methodology were carried out to regulate the operating conditions and optimize the medium. The results showed that the optimized gas production of biodegradable lignite reached 79.29 mL (54.32% methane)/2 g coal, which is much higher than the other microbial conversions of lignite to methane reported to date. Furthermore, the combined most probable number counting method and high-throughput sequencing technique revealed that the main bacteria in the fermentation process are acid forming bacteria, sulfate-reducing bacteria and methanogenic bacteria. This study provides new insight into methanation and the clean utilization of lignite.

Biotechnology of Microorganisms from Coal Environments: From Environmental Remediation to Energy Production.

Simple SummaryDespite the wide perception that coal environments are extreme habitats, they harbor resident microbial communities. Coal-associated habitats, such as coal mine areas/drainages, spoil heaps, and coalbeds, are defined as complex ecosystems with indigenous microbial groups and native microecological networks. Resident microorganisms possess rich functional potentials and profoundly shape a range of biotechnological processes in the coal industry, from production to remediation.It was generally believed that coal sources are not favorable as live-in habitats for microorganisms due to their recalcitrant chemical nature and negligible decomposition. However, accumulating evidence has revealed the presence of diverse microbial groups in coal environments and their significant metabolic role in coal biogeochemical dynamics and ecosystem functioning. The high oxygen content, organic fractions, and lignin-like structures of lower-rank coals may provide effective means for microbial attack, still representing a greatly unexplored frontier in microbiology. Coal degradation/conversion technology by native bacterial and fungal species has great potential in agricultural development, chemical industry production, and environmental rehabilitation. Furthermore, native microalgal species can offer a sustainable energy source and an excellent bioremediation strategy applicable to coal spill/seam waters. Additionally, the measures of the fate of the microbial community would serve as an indicator of restoration progress on post-coal-mining sites. This review puts forward a comprehensive vision of coal biodegradation and bioprocessing by microorganisms native to coal environments for determining their biotechnological potential and possible applications.

Methanogenic archaea in subsurface coal seams are biogeographically distinct: an analysis of metagenomically-derived mcrA sequences.

The production of methane as an end-product of organic matter degradation in the absence of other terminal electron acceptors is common, and has often been studied in environments such as animal guts, soils and wetlands due to its potency as a greenhouse gas. To date, however, the study of the biogeographic distribution of methanogens across coal seam environments has been minimal. Here, we show that coal seams are host to a diverse range of methanogens, which are distinctive to each geological basin. Based on comparisons to close relatives from other methanogenic environments, the dominant methanogenic pathway in these basins is hydrogenotrophic, with acetoclastic being a second major pathway in the Surat Basin. Finally, mcrA and 16S rRNA gene primer biases were predominantly seen to affect the detection of Methanocellales, Methanomicrobiales and Methanosarcinales taxa in this study. Subsurface coal methanogenic community distributions and pathways presented here provide insights into important metabolites and bacterial partners for in situ coal biodegradation.

Proteomic analysis of Fusarium sp. NF01 revealed a multi-level regulatory machinery for lignite biodegradation

Proteomic analysis provides vital bioinformation for revealing the mechanisms of coal biodegradation. Yet, proteomics-based studies of coal biodegradation are generally lacking. We first studied the physio-chemical changes in lignite biodegradation by a previously isolated fungus (Fusarium sp. NF01). The strain was able to degrade lignite showing significant changes in the ultraviolet–visible absorbance, surface structure and a 40.9% increased free radical concentration of residual lignite. Subsequently, isobaric tandem mass tags (TMT) and bioinformatic analysis were used for the quantitative and qualitative analyses of Fusarium sp. NF01 secretome. The expression levels of 62 proteins were significantly altered in the lignite-supplemented medium: 20 proteins were upregulated (fold-change, FC ≥ 2; P-value ≤0.05) and 42 proteins were downregulated (FC ≤ 0.5, P-value ≤0.05). Bioinformatic analysis indicated that Fusarium sp. NF01 acclimatized to the lignite-rich environment by regulating the expression of proteins involved in defense, lignite degradation, detoxification, and cellular metabolism. These findings may help promote sustainable and value-added coal utilization.

Sequential degradations of Dananhu lignites by Nocardia mangyaensis and Bacillus licheniformis

The sequential degradation of coal by two bacterial species was one of the effective methods to improve the coal biodegradation rates. In this paper, two bacteria N. mangyaensis and B. licheniformis were selected to degrade Dananhu lignite sequentially. The biodegradation rates and products of Dananhu lignites by two degradation ways were investigated and characterized, respectively. The results indicated the best way for sequential degradation of Dananhu lignite was to use N. mangyaensis first and then B. licheniformis (represented as “N. mangyaensis → B. licheniformis” order), in which the highest degradation rate reached 82.1%. On the contrary, the degradation rate attained 75.5% with the order of “B. licheniformis → N. mangyaensis”. The compositions and structures of solid and liquid bioproducts by two ways were analyzed. The side chains in oxidized lignite were prone to be degraded by N. mangyaensis and the aromatic skeletons were attacked by B. licheniformis. Therefore, the sequential degradation order of “N. mangyaensis → B. licheniformis” was the effective way for Dananhu lignite.

Development of a saprophytic fungal inoculum for the biodegradation of sub-bituminous coal

The rhizospheres of the weeds Ageratum conyzoides, Axonopus compressus, Emilia coccinea, Synedrella nodiflora, Urena lobata and Sida acuta from a sub-bituminous coal mining site and a control site, without coal discards, were screened for new fungi with ability to degrade sub-bituminous coal in the laboratory. The isolates were identified by cultural and molecular methods. Seventeen out of the sixty-one fungal isolates tested could utilize sub-bituminous coal as an energy source. Upon further evaluation, only seven of these were promising candidates for coal biodegradation, and they were assayed for their biosolubilization and depolymerization activities to determine their mechanisms of coal biodegradation. Based on the accumulation of humic acid (HA), which is the marker for biosolubilization, Mucor circinelloides and Aspergillus tubingensis were the most active. On the other hand, Cunninghamella bertholletiae, Simplicillium subtropicum, Penicillium daleae and Trichoderma koningiopsis were the highest producers of fulvic acid (FA), the indicator of depolymerization. Purpureocillium lilacinum produced the lowest yields of both HA and FA compared to the other six coal-degrading candidates. The presence of laccase in Trichoderma koningiopsis, Penicillium daleae and Simplicillium subtropicum suggests a role for this enzyme in the enhancement of the coal biodegradation process. However, the inability to amplify the laccase gene in Cunninghamella bertholletiae indicates that another enzyme probably aids its coal bioconversion. The current investigation highlights the potentials of these strains in harnessing biotechnological processes of sub-bituminous coal conversion into value-added products, which could be extended to the bioremediation of coal-polluted soils. The fungi with the highest coal bioconversion capabilities belonged to Ascomycota and Zygomycota and were found in the rhizospheres of the weeds Emilia coccinea, Ageratum conyzoides and Axonopus compressus.

Enhancements of Mixed Surfactants on Wucaiwan Coal Biodegradation by Nocardia Mangyaensis

Enhancements of Mixed Surfactants on Wucaiwan Coal Biodegradation by Nocardia Mangyaensis