J Ind Microbiol Biotechnol (2007) 34:625–631 DOI 10.1007/s10295-007-0223-7 123 ORIGINAL PAPER Degradation of low rank coal by Trichoderma atroviride ES11 M. Estela Silva-Stenico · Caryn J. Vengadajellum · Hussnain A. Janjua · Sue T. L. Harrison · Stephanie G. Burton · Don A. Cowan Received: 9 January 2007 / Accepted: 19 April 2007 / Published online: 29 June 2007  Society for Industrial Microbiology 2007 Abstract A new isolate of Trichoderma atroviride has been shown to grow on low rank coal as the sole carbon source. T. atroviride ES11 degrades »82% of particulate coal (10 g l ¡1 ) over a period of 21 days with 50% reduction in 6 days. Glucose (5 g l ¡1 ) as a supplemented carbon source enhanced the coal solubilisation eYciency of T. atroviride ES11, while 10 and 20 g l ¡1 glucose decrease coal solubilisa- tion eYciency. Addition of nitrogen [1 g l ¡1 (NH 4 ) 2 SO 4 ] to the medium also increased the coal solubilisation eYciency of T. atroviride ES11. Assay results from coal-free and coal- supplemented cultures suggested that several intracellular enzymes are possibly involved in coal depolymerisation pro- cesses some of which are constitutive (phenol hydroxylase) and others that were activated or induced in the presence of coal (2,3-dihydrobiphenyl-2,3-diol dehydrogenase, 3,4-dihydro phenanthrene-3,4-diol dehydrogenase, 1,2-dihy- dro-1,2-dihydroxynaphthalene dehydrogenase, 1,2-dihydro- 1,2-dihydroxyanthracene dehydrogenase). GC-MS analysis of chloroform extracts obtained from coal degrading T. atro- viride ES11 cultures showed the formation of only a limited number of speciWc compounds (4-hydroxyphenylethanol, 1,2-benzenediol, 2-octenoic acid), strongly suggesting that the intimate association between coal particles and fungal mycelia results in rapid and near-quantitative transfer of coal depolymerisation products into the cell. Keywords Low rank coal · Biodegradation · Trichoderma atroviride · Intracellular enzymes Introduction Previous studies have shown that certain fungi and bacteria are able to degrade lignites and sub-bituminous coals [1–5]. However, the mechanisms of coal solubilisation are not fully understood. Coal biodegradation is thought to involve a complex array of constituents and processes involving hydrolytic enzymes [6], oxidative enzymes [7], acidic/alkaline sub- stances [8], chelating agents [9], and surfactants [10]. It is generally believed that oxidative enzymes are the primary factors in coal depolymerisation [11, 12]. However, the exact pathway involved in coal degradation is dependent both on the strain used and the type of coal. Interest in coal solubilization is largely stimulated by the prospect of recovering coal derived organic intermedi- ates [13] as chemical products for the Wne chemical enti- ties [14]. Several strategies have been developed in attempts to enhance the yield of coal biosolubilisation products, including the use of cell-free extracts [15], and the addition of chelating agents [9, 16] or alkali [8]. The generation of coal derived-organic intermediates is thought to involve one or more of the following: depolymerisation of aromatic structures which are linked by aliphatic and ether bridges [17], oxidative and decarb- oxylative changes to the monomers/oligomers, removal of sulfur, nitrogen and/or metals [18] and ring cleavage reactions. However, the fact that previous mechanistic studies on coal degradation have used numerous diVerent microbial species [19] and coal types makes it diYcult to establish valid comparisons. M. E. Silva-Stenico · H. A. Janjua · D. A. Cowan (&) Advanced Research Centre for Applied Microbiology, Department of Biotechnology, University of the Western Cape, Private Bag X17, Bellville, 7535 Cape Town, South Africa e-mail: dcowan@uwc.ac.za C. J. Vengadajellum · S. T. L. Harrison · S. G. Burton Bioprocess Engineering Research Unit, Department of Chemical Engineering, University of Cape Town, Rondebosch, 7700 Cape Town, South Africa