Characterization of fungal inoculum used in soil bioremediation

Abstract

Studies have indicated the capacity of basidiomycetes to degrade recalcitrant organopollutants. However, the age of the fungal inoculum to obtain a more effective degradation has not been defined. The criterion used is total colonization of the substrate. Psilocybe castanella CCB444 and Lentinus crinitus CCB274 have been evaluated in soils containing hexachlorobenzene. In the present study, the physiological conditions of the fungal inocula were characterized on solid substrate (sugarcane bagasse, starch and soy flour). Colonization of the substrate, loss of organic matter, pH variation, organic carbon, total nitrogen, fungal biomass and enzymatic activity were evaluated over 30 days of incubation. Colonization of the substrate was almost complete after 20 days for both species, with about 90% of organic matter remaining on the substrates. The pH continued to be acid during incubation. The highest enzymatic production was observed at 10 days for L. crinitus and at 5 days for P. castanella. The fungi presented growth up to 30 days. The C/N ratio of the inocula showed little variation. The use among 10 and 15-day-old inoculum is adequate since sufficient nutrients are left to guarantee survival of the fungus, vigorous colonization of the substrate, a growing biomass and an active enzymatic system, thus permitting fungal growth in soil.

Removal of high-molecular weight polycyclic aromatic hydrocarbons

“…This drastic variation of HMW-PAH biodegradation rate was probably associated with the depletion of the glycerol and essential nutrients such as nitrogen and phosphorus. 29 Decrease of pH compared with the initially determined value was observed in all reactors studied. This pH decrease may have been the result of microbial metabolism, but the soil buffer property may also have contributed to the pH decrease.…”

Physiological Characterization of Fungal Inoculum for Biotechnological Remediation of Soils

“…The quick colonization of solid substrates by filamentous fungi, as in the case of PCP-soil, could overestimate fungal colonization when visually observed. That happens because of the extension mode of the hyphae, which initially provide the superficial colonization of the substrate, forming a thin layer of mycelium that only afterwards penetrate the substrate mass (Gowthaman et al 2001, Ballaminut andMatheus 2007). This was as observed in the inocula assessed (T5, T10, T15 and T20).…”

“…A value was stipulated for each replication according to the soil's percent colonization, judged by six independent observers (Ballaminut and Matheus 2007).…”

“…Therefore, such fungus has been assessed in bioremediation processes for decontamination of soils containing organochlorine compounds (Matheus et al 2003). For bioremediation process, the inoculum must be produced in large scale, with the same technology employed in the cultivation of edible mushrooms (Ballaminut and Matheus 2007). The fungal mycelium's colonization capacity of the substrate is the main quality criterion for the inoculum, which is generally employed at the physiological age of 20 days (Bononi 1997, Lamar andWhite 2001;Matheus 2003).…”

“…The fungal mycelium's colonization capacity of the substrate is the main quality criterion for the inoculum, which is generally employed at the physiological age of 20 days (Bononi 1997, Lamar andWhite 2001;Matheus 2003). However, the physiological conditions that knowingly enhance fungal inoculum's strength vary according to growth time on solid substrate (Ballaminut and Matheus 2007) and may interfere in the efficiency of degradation of the pollutant present in the soil to be treated. A study on L. crinitus cultivated in liquid medium defined both the initial and the exponential growth phase of that fungus; biomass was determined after dry weight, along with ergosterol quantification (Silva et al 2010).…”