The white-rot fungus Phanerochaete chrysosporium produces extracellular peroxidases (ligninase and Mn-peroxidase) believed to be involved in lignin degradation. These extracellular enzymes have also been implicated in the degradation of recalcitrant pollutants by the organism. Commercial application of ligninase has been proposed both for biomechanical pulping of wood and for wastewater treatment. In vitro stability of lignin degrading enzymes will be an important factor in determining both the economic and technical feasibility of application for industrial uses, and also will be critical in optimizing commercial production of the enzymes. The effects of a number of variables on in vitro stability of ligninase and Mn-peroxidase are presented in this paper. Thermal stability of ligninase was found to improve by increasing pH and by increasing enzyme concentration. For a fixed pH and enzyme concentration, ligninase stability was greatly enhanced in the presence of its substrate veratryl alcohol (3,4-dimethoxybenzyl alcohol). Ligninase also was found to be inactivated by hydrogen peroxide in a second-order process that is proposed to involve the formation of the unreactive peroxidase intermediate Compound III. Mn-peroxidase was less susceptible to inactivation by peroxide, which corresponds to observations by others that Compound III of Mn-peroxidase forms less readily than Compound III of ligninase.
Various in situ or pump and treat systems are used for the remediation and/or containment of groundwater. Tougher air pollution regulations have mandated the implementation of pump and treat strategies that minimize losses of organic compounds because of uncontrolled air stripping. A modified bench‐scale sequencing batch reactor (SBR) was intermittently closed to test its flexibility and applicability as a system for the treatment of Jet Fuel‐4 (JP‐4)‐contaminated groundwater associated with free product recovery. The SBR was operated for 180 days on JP‐4‐contaminated water that contained high concentrations of monoaromatic hydrocarbons. Typically, the effluent contained less than 50 μ g/L of total petroleum hydrocarbons with much lower levels for the benzene, toluene, ethyl benzene, and xylenes and met the discharge levels required by most state regulatory agencies.
The white rot fungus Phanerochaete chrysosporium and its extracellular enzyme lignin peroxidase are both known to catalyze the transformation and, in many cases, the degradation of several hazardous compounds and are, therefore, promising candidates for application in hazardous waste treatment. The application of P. chrysosporium in large-scale waste treatment and commercial production of lignin peroxidase has been impeded by the lack of bioreactor systems yielding consistent production of high levels of lignin peroxidase under long-term steady state conditions and controlled growth of the fungus. The use of innovative biofilm systems, which minimize intensive shear and provide for fungal growth as a biofilm, was investigated. The viability of the use of a hollow fiber reactor and a stirred tank reactor modified into a unique silicone membrane reactor for the cultivation of P. chrysosporium and production of high levels of lignin peroxidase was demonstrated. The membrane reactor utilizes silicone tubing as a growth support and for oxygenation. The silicone membrane reactor was operated using a repeated batch technique, consisting of alternating growth and production phases, to yield production of lignin peroxidase over a period of 5 weeks and appears promising for application as a hazardous waste treatment process.
In Alaska, the procedures used to quantify petroleum in organic soil are complicated by the presence of natural organic matter (NOM). A percentage of what appears to be contamination in some soil samples is actually NOM. The “contamination” derived from NOM (i.e., biogenic interference) cannot be quantified separately from petroleum using currently available analytical methods unless a “background” sample that is known to be uncontaminated can be obtained. Proving that a background sample is truly uncontaminated is often problematic, if not impossible. In the research described here, the concentration of biogenic interference in petroleum contaminated soils was inferred using pyrolysis-gas chromatography/mass spectrometry without a background sample by quantifying the concentration of a suite of compounds called “biogenic indicators.” These indicators were selected because they are present in NOM, not present in petroleum, and similar in structure and origin to biogenic interference. This paper discusses the method and its limitations.
