Effect of coal pretreatment on brown coal biosolubilisation by Fusarium oxysporum 1101

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1 Effect of coal pretreatment on brown coal biosolubilisation by Fusarium oxysporum 1101 Bartosz STRZELECKI, Natalia KWIATOS, Stanisław BIELECKI Keywords: brown coal pretreatment; biosolubilization; lignite Abstract: Brown coal is one of the most important sources of energy in the world, next to crude oil, natural gas and hard coal. Unfortunately, there are many factors, which disqualify the use of this material for energy production, among others: low calorific value, emissions of NOx and SOx, problems with mining, etc. Therefore, there is a need for developing technologies which will enable brown coal liquefaction. Biosolubilization is a process that uses microorganisms for this purpose. The aim of this study was to investigate the effect of coal pretreatment on the biosolubilization, using Fusariumoxysporum Pretreatment of raw material with HNO3 seems to be the most effective process. It resulted with 100% liquefaction of brown coal after 4 days of incubation with the fungi. Data obtained in infrared spectra showed changes in coal structure and confirmed a positive influence of nitric acid on coal biosolubilization performed with F. oxysporum Introduction Brown coal next to crude oil, natural gas and hard coal is one of the most important sources of non-renewable energy. It is used mainly for the production of heat and electricity. World coal resources are estimated to be 1,024.7 billion tons, but with current state of technology man is able to extract only about 207 billion tons. This amount is sufficient for about 250 years, while oil and natural gas will be exhausted within years (Thielemann et al., 2007). Despite its lower calorific value compared to other energy sources, the use of brown coal in electricity production increases and in 2008 it reached 41 %. However, such a high use of lignite is not fully acceptable due to the high carbon dioxide emissions per unit of energy obtained (94.60 kg CO2/GJ) compared to other fossil fuels, for example petroleum kg CO 2 /GJ (Tajduś and Dubiński, 2011). Another factor disqualifying the use of coal as a source of electricity is high emission of greenhouse gases (NOx and SOx) and ashes. Therefore, the so-called Clean Coal Technologies are in demand for coal conversion Institute of Technical Biochemistry, Faculty of Biotechnology and Food Sciences, Lodz University of Technology (LUT), Łódź, Poland

2 126 PhD Interdisciplinary Journal to cleaner fuels and minimization of pollution (Tajduś et al., 2011). One of such methods is thermochemical coal liquefaction. This process is based on a variety of chemical reactions carried out under drastic conditions, which require large amounts of energy and expensive equipment. Moreover, during the process large amounts of carbon dioxide are released (of Trade and Industry, 1999). It provoked scientists around the world to conduct research on biological solubilization of coal. Such process, compared to chemical reactions, occurs at low temperatures and at normal pressure, which is advantageous for economic reasons (Yuan et al., 2006). Coal biosolubilization has already been described in literature (Basaran, 2003; Ralph and Catcheside, 1997; Faison, 1991; Klein et al., 1999). It is a process that occurs with the participation of microorganisms (fungi and bacteria), its effectiveness is influenced by many agents (substances) produced by microorganisms. Lignite biosolubilization may occur due to enzymatic reactions or by alkali, chelators and biosurfactants production (Torzilli and Isbister, 1994; Fakoussa and Hofrichter, 1999; Strandberg and Lewis, 1987). Enzymatic biosolubilization of lignite is performed by ligninolytic enzymes such as: laccase, lignin peroxidase and Mn-dependent peroxidase, since coal has a similar structure to lignin. The presence of humic components, soluble in basic ph, makes the alkaline substances produced by microorganisms highly helpful in the process. Biosurfactants are responsible for reducing the surface tension in hydrophobic regions of coal, increasing its solubility. However, microbially produced surface-active agents do not act as a sole factor biosolubilization is a consequence of the activity of biosurfactants and enzymes (Fakoussa and Hofrichter, 1999; Sekhola et al., 2013; Willmann and Fakoussa, 1997; Holker et al., 1999). Nevertheless, in order to conduct the process of biosolubilization with the mentioned factors, first the structure of coal should be loosen and oxidized. The process of pretreatment can be done with various chemicals and solvents (Kai-yi et al., 2012; Novikova et al., 2010; Semenova et al., 2006; Hofrichter et al., 1997; Huang et al., 2013). The following paper describes the effect of such factors on the biosolubilization with Fusariumoxysporum Materials and methods Microorganisms Fusariumoxysporum 1101 isolated from brown coal mine in Bełchatów, Poland, by Manu de Groeve, PhD and his group, was used. The strain is a part of the microorganisms collection of the Institute of Technical Biochemistry, Lodz University of Technology. Media Czapek-Dox medium was used for storage of the strain: (30 g/l), yeast extract (5.0 g/l) NaNO 3 (3.0 g/l), K 2 PO 4 (1.0 g/l), MgSO 4 (0.5 g/l), KCl (0.5 g/l), FeSO 4 (0.01 g/l), Agar (15.0 g/l). Cultivation and biosolubilization were performed on solid Czapek- Dox with addition of sodium glutamate (2 g/l) (Holker et al., 1995).

3 127 Brown coal pretreatment Brown coal from The Bełchatów Coal Mine was used in the study. 1-3 mm coal pieces were subjected to the pretreatment processes. The conditions were optimized in accordance with available literature (Kai-yi et al., 2012; Novikova et al., 2010; Semenova et al., 2006): 8 M HNO g of coal per 1 ml HNO 3, 48 h incubation at room temperature, rinsing with distilled water till ph is around 7, drying; 30 % H 2 O g of coal per 1 ml H 2 O 2, 48 h incubation at room temperature, rinsing with distilled water till ph is around 7, drying; 5 % KMnO g of coal per 1 ml KMnO 4, 4 h incubation at 90 C, rinsing with distilled water till ph is around 7, drying; Ozonation in chloroform 25 g of coal, 80 g/m 3 ozon at flow rate 0.1 dm 3 /min. The process lasted for 6 h at 25 C with intensive mixing. Then the coal was washed with acetone till the solvent lost its color. Biosolubilization of brown coal by F. oxysporum 1101 The plates with solid Czapek-Dox were inoculated with F. oxysporum 1101 and incubated for 7 days at 29 C. Then the brown coal pieces were placed on the mycelium and left for observation at 29 C. After a few days the carbon pieces were removed, rinsed with water, dried and weighed. The percentage of liquefaction was calculated with the following formula: m 1 initial weight of coal, m 2 weight after biosolubilization. %liquefaction = m 1 m 2 m 1 100% (1) FTIR analysis of coal and products of biosolubilization Infrared spectroscopy can be used to determine the specific chemical groups of atoms in the structure of coal and its biosolubilization products. The pretreated coals were analyzed using an infrared spectrum analyzer (Nicolet 6700 FT-IR, Thermo Scientific) with light wave lengths from 4000 cm 1 to 500 cm Results and discussion The pretreated coal was further used in biosolubilization by F. oxysporum 1101 and the effectiveness of this process was assessed. The results were supported by FTIR analysis.

4 128 PhD Interdisciplinary Journal 3.1. Influence of pretreatment on the effectiveness of biosolubilization The choice of pretreatment is important, as it enhances the brown coal biosolubilization process through oxidation and loosening of coal structure. The analysis was done by placing pretreated coal beats size 3-1 mm on a plate with fungal mycelium. The results are presented in the figures below (Fig. 1, 2, 3, 4, 5). F. oxysporum 1101 shows very low capability of unpreatreated coal solubilization, which is shown in Fig. 1. After 7 days of the process, the level of biosolubilization did not exceed 5 %, after 35 days the level reached only 10 %. Such low values are probably due to the compact structure of native coal. However, comparing the obtained results with other literature data, the results for F. oxysporum 1101 are not the most disappointing in fungi isolated from Chinese lignite after 11 days the process the solubilization did not exceed 1 % (Sudong et al., 2009), bacterium Pseudomonas putida after 14 days is able to process only 11 % (Machnikowska et al., 2002). Fig. 2 presents brown coal biosolubilization after pretreatment with 5 % KMnO 4. The loss of coal mass after the process is similarly low as for unpretreated lignite. After 2 first days no changes were observed, after 11 days of incubation biosolubilization Fig. 1. The degree of raw coal solubilization by F.oxysporum Fig. 2. The degree of coal liquefaction by F. oxysporum 1101 after treatment with 5 % KMnO 4.

5 129 reached only 6 %. Such low values of the parameter of the test are most likely caused by deposition of manganese oxide on the surface of coal, which hinders the operation of the factors affecting biosolubilization. The available literature does not offer information on coal pretreatment with KMnO 4. Fig. 3. The degree of coal liquefaction by F. oxysporum 1101 after pretreatment with ozone. Another variant of the study was carried out by applying ozone and an ozoneoxygen mixture (80 mg O 3 /dm 3 ) in chloroform for lignite pretreatment. A 10 % level of biosolubilization was obtained after 2 days of the process. In the next days the level grew slowly up to 25 %. Probably the ozone dose was not high enough to loosen and oxidize the structure. Literature does not provide any information about the use of ozone for lignite pretreatment. Fig. 4. The degree of coal liquefaction by F. oxysporum 1101 after pretreatment with 30 % H 2 O 2. Treating coal with 30 % H 2 O 2 is an efficient method of pretreatment, but because of the high concentration of the oxidizing agent, it is quite dangerous. As it can be seen in Fig. 4 during the first two days the biosolubilization level was low (15 %), but after 8 days of incubation 71 % coal was solubilized, and after 14 days almost 100 % of coal was solubilized. Coal pretreatment with nitric acid, as presented in Fig. 5, is the most effective method for this purpose compared with other methods. Coal was processed in 60 %

6 130 PhD Interdisciplinary Journal for 2 days and after 4 days 100 %was already solubilized. Literature mentions other examples of using 0.8 M HNO 3 for coal pretreatment. Fungi isolated from Chinese coal were able to process coal pretreated in such a way in around 33 % in 11 days, while P. putida was able to solubilize 90 % of coal in 14 days (Machnikowska et al., 2002; Sudong et al., 2009). The presented research shows that F. oxysporum 1101 has a very good biosolubilizing ability. However, it should be noted that among the tested methods of pretreatment these have the best efficiency which are conducted in drastic conditions and at a high concentration of oxidizing agents, which unfortunately cannot be used on a larger scale. Therefore, one of the objectives in further research is searching for other methods that allow an efficient and effective process of lignite biosolubilization FTIR spectra of the pretreated coal and biosolubilization products FTIR spectrum is presented in Fig. 6. The main peaks registered by the apparatus at a suitable wave number for the following functional groups: cm 1 : hydroxyl groups, cm 1 : aliphatic group CH, cm 1 : carbonyl groups, carboxyl and ester bonds, cm 1 : aromatic compounds, 1300 to 1000 cm 1 : ether bond and ester groups. The first peak at a wave number 3400 cm 1 relates to hydroxyl groups. As presented in Fig. 6 all of the spectra possess this peak in varying degrees of intensity, which indicates a fairly large share of these groups in the coal structure. The next peak comes from vibration of aliphatic CH carbons at cm 1, it was difficult to notice it for the sample subjected to ozonization and it was not observed in the spectrum of carbon treated with KMnO 4. Treatment with the mentioned chemicals may result in a decrease in the number of aliphatic C-H bonds. Another characteristic minimum for the wave number in the range cm 1 is the peak which Fig. 5. The degree of coal liquefaction by F. oxysporum 1101 after treatment with 8M HNO 3.

7 131 Fig. 6. FTIR spectra for the pretreated carbon. relates to carbonyl, carboxyl groups and ester bonds. As before, this peak was not observed for the spectrum of carbon treated with KMnO 4. The peak at cm 1 (aromatic compounds) is observed for all samples as coal is build mainly of aromatic units. The last characteristic peak ( cm 1 ) can be observed for ester and ether bonds. It is significant for coal pretreated with H 2 O 2 and HNO 3, which implies that these pretreatments introduce oxygen in forms of ether and ester bonds. 4. Conclusions The presented results prove F. oxysporum 1101 biosolubilization abilities for the studied brown coal. For the process to be more effective brown coal should be pretreated with oxidizing agents and substances that loosen its structure. The best results were obtained after treatment of coal with hydrogen peroxide and nitric acid. As one can conclude from FTIR spectra, the action of the above factors causes the introduction of oxygen into the coal structure (wave number cm 1 ). The structure changed in that way facilitates access of all kinds of solubilizing agents as well as oxidoreductases which are secreted by the strain also responsible for the biosolubilization process. References Basaran, Y. (2003), Bio - liquefaction/solubilization of low - rank turkish lignites and characterization of the products, Energy & Fuels pp Faison, B. D. (1991), Biological conversion coal, Critical Reviews in Biotechnology 4, Fakoussa, R. and M. Hofrichter (1999), Biotechnology and microbiology of coal degradation, Applied Microbiology and Biotechnology 52, Hofrichter, M., F. Bublitz and W. Fritsche (1997), Fungal attack on coal ii. solubilization of low-rank coal by filamentous fungi, Fuel Processing Technology 52, Holker, U., R. M. Fakoussa and M. Hofer (1995), Growth substrates control the ability of fusarium oxysporum to solubilize low-rank coal, Applied Microbiology and Biotechnology 44,

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INFLUENCE OF FE, CU, MN, ZN, CO CHELATORS ON THE BIOTRANSFORMATION OF HUMIC SUBSTANCES OF LIGNITE

INFLUENCE OF FE, CU, MN, ZN, CO CHELATORS ON THE BIOTRANSFORMATION OF HUMIC SUBSTANCES OF LIGNITE G. Angelova 1, K. Chakalov 1, T. Popova 1 and V. Savov 1 ROMB ltd, 1 Aboba Str. 166 Sofia, Bulgaria E-mail: