Fungal colonization and enzyme-mediated metabolism of waste coal by Neosartorya fischeri strain ECCN 84

Abstract

Colonization and oxidative metabolism of South African low-rank discard coal by the fungal strain ECCN 84 previously isolated from a coal environment and identified as Neosartorya fischeri was investigated. Results show that waste coal supported fungal growth. Colonization of waste coal particles by N. fischeri ECCN 84 was associated with the formation of compact spherical pellets or sclerotia-like structures. Dissection of the pellets from liquid cultures revealed a nucleus of “engulfed” coal which when analyzed by energy dispersive X-ray spectroscopy showed a time-dependent decline in weight percentage of elemental carbon and an increase in elemental oxygen. Proliferation of peroxisomes in hyphae attached to coal particles and increased extracellular laccase activity occurred after addition of waste coal to cultures of N. fischeri ECCN 84. These results support a role for oxidative enzyme action in the biodegradation of coal and suggest that extracellular laccase is a key component in this process.

Biological conversion of low-grade coal discard to a humic substance-enriched soil-like material

“…LAC and MnP), which have been reported in several studies to be responsible for fungal breakdown of coal Zavarzina et al 2004;Grinhut et al 2007;Tao et al 2010). Furthermore, studies in our laboratory on the fungal metabolism of coal discard confirmed that coal degradation by Neosartorya fischeri ECCN84, isolated from coal discard dumps, occurs coincident with elevated extracellular LAC (Sekhohola et al 2014). It was previously postulated that fungal interaction with coal particles results in bioconversion of this substrate into a mixture of heterogeneous macromolecules that are mainly humic acids (Cohen and Gabriele 1982;Henning et al 1997;Catcheside and Ralph 1999;Dong et al 2006).…”

“…The concept of fungal depolymerization and solubilization of low rank coal is not novel and has been investigated and reported (Cohen and Gabriele 1982;Ralph and Catcheside 1997;Fritsche 1996, 1997;Hofrichter et al 1999;Willmann and Fakoussa 1997a, b;Igbinigie et al 2008;Sekhohola et al 2013Sekhohola et al , 2014. However, most of the work on coal bio-solubilization is from laboratory based studies where processes are constrained and do not necessarily simulate what happens in the field.…”

“…Consequently coal bio-solubilization has not been fully explored as a rehabilitation methodology for use at commercial scale. Even so, several studies clearly show that direct contact between metabolically active biocatalysts and substrate coal facilitates degradation of this recalcitrant material (Mukasa-Mugerwa et al 2010;Tripathi et al 2010;Klein et al 2013;Oboirien et al 2013;Sekhohola et al 2014;Hazrin-Chong et al 2014).…”

“…An extensive screening exercise followed and resulted in the isolation of among other fungi, the ascomycete Neosartorya fischeri (Igbinigie et al 2008). This fungus was shown to actively degrade coal in a perfusion fixed-bed bioreactor, used to simulate the coal discard dump environment (Igbinigie et al 2008), in the C. dactylon/coal rhizosphere (Igbinigie et al 2010;Mukasa-Mugerwa et al 2010), and in vitro (Sekhohola et al 2014). Based on these findings, an integrated model was proposed to describe some of the interactions in the rhizosphere that transform coal discard to a humic acid-like substance (HS) enriched medium capable of supporting establishment of a healthy vegetation (Sekhohola et al 2013).…”

Geochemical Study of Weathered Coal, a Co-Substrate for Bioremediation of South African Coal Discard Dumps

“…Indeed, other forms of weathered coal including coal from discard dumps and a highly oxidized coal obtained from an aged waste dump were unable to support fungal-plant bioremediation and revegetation [20]. Thus, the geochemical study of outcrop-weathered coal described here was undertaken to provide insight into the role of this material as a mineral/carbon source to ensure biologically induced humic acid (HA)-like substance enrichment of discard and spoil to facilitate breakdown of the carbonaceous material [21][22][23], plant-fungal mutualism [24,25], and revegetation without the need for topsoil [20,26]. Furthermore, a good understanding of the geochemistry of this outcrop weathered coal may improve our understanding of the geological processes involved in coal weathering in situ.…”