Gyu Hyeok Kim

Biotechnological procedures to select white rot fungi for the degradation of PAHs

White rot fungi are essential in forest ecology and are deeply involved in wood decomposition and the biodegradation of various xenobiotics. The fungal ligninolytic enzymes involved in these processes have recently become the focus of much attention for their possible biotechnological applications. Successful bioremediation requires the selection of species with desirable characteristics. In this study, 150 taxonomically and physiologically diverse white rot fungi, including 55 species, were investigated for their performance in a variety of biotechnological procedures, such as dye decolorization, gallic acid reaction, ligninolytic enzymes, and tolerance to four PAHs, phenanthrene, anthracene, fluoranthene, and pyrene. Among these fungi, six isolates showed the highest (>90%) tolerance to both individual PAH and mixed PAHs. And six isolates oxidized gallic acid with dark brown color and they rapidly decolorized RBBR within ten days. These fungi revealed various profiles when evaluated for their biotechnological performance to compare the capability of degradation of PAHs between two groups selected. As the results demonstrated the six best species selected from gallic acid more greatly degraded four PAHs than the other isolates selected via tolerance test. It provided that gallic acid reaction test can be performed to rank the fungi by their ability to degrade the PAHs. Most of all, Peniophora incarnata KUC8836 and Phlebia brevispora KUC9033 significantly degraded the four PAHs and can be considered prime candidates for the degradation of xenobiotic compounds in environmental settings.

Bioleaching of spent Zn-Mn or Ni-Cd batteries by Aspergillus species.

This research explores the recovery of metals from spent Zn-Mn or Ni-Cd batteries by a bioleaching using six Aspergillus species. Two different nutrients, malt extract and sucrose, were used to produce different types of organic acids. Oxalic acid and citric acid were shown to be the dominant organic acid in malt extract and sucrose media, respectively. In the bioleaching, the metal removal was higher in sucrose media than malt extract. All species, except A. niger KUC5254, showed more than 90% removal of metals from Zn-Mn battery. For Ni-Cd battery, more than 95% of metals was extracted by A. niger KUC5254 and A. tubingensis KUC5037. As a result, A. tubingensis KUC5037 which is a non-ochratoxigenic fungus was considered to have the greatest potential for improving the safety and efficiency of the bioleaching.

Leptographium bistatum sp. nov., a new species with a Sporothrix synanamorph from Pinus radiata in Korea

Radiata pine (Pinus radiata) lumber from Australia, Chile, and New Zealand is imported into Korea where it represents one of the most important sources of timber. Blue stain of this timber is a serious problem for which an integrated control strategy is being developed. One of the fungi that has been isolated from stained radiata pine sapwood in Korea is a Leptographium sp. that has a distinct Sporothrix synanamorph. The aim of this study was to classify this fungus. Morphological comparisons showed that this fungus is distinct from all other species of Leptographium and especially L. elegans and L. francke-grosmanniae that also have Sporothrix synanamorphs. Comparisons of sequence data for the ITS2 and part of the 28S rDNA genes as well as the beta-tubulin gene also confirmed that this fungus represents an undescribed taxon, described here as Leptographium bistatum sp. nov.

A new Leptographium species associated with Tomicus piniperda infesting pine logs in Korea.

During the course of a survey of sapstaining fungi in Korea, a Leptographium was isolated from Pinus densiflora and P. koraiensis logs, infested with the bark beetle Tomicus piniperda. The fungus grew optimally at 25 C on 2% malt extract agar and showed a high level of tolerance to cycloheximide. The Leptographium has unusually short conidiophores and is morphologically similar to L. pini-densiflorae, L. lundbergii, L. yunnanense, and the Leptographiumn anamorph of Ophiostoma crassivaginatum. Comparisons of DNA sequence data for three gene regions, as well as morphological characteristics, confirmed that this fungus represents an undescribed taxon. We consequently provide the name Leptographium koreanum sp. nov. for it here.

Phylogenetic analysis of major molds inhabiting woods and their discoloration characteristics. Part 1. Genus Trichoderma

Abstract The genus Trichoderma Persoon is a cosmopolitan genus consisting of more than 104 species and is commonly found on wood surfaces as a mold where it affects the appearance. Little attention has been given to wood-colonizing Trichoderma species and few studies are dedicated for identification of Trichoderma at the level of species. In the present study, up to 142 isolates were obtained from various wood samples. One Gliocladium and ten Trichoderma species were identified by morphological and molecular analysis. T. atroviride (30.3%) was the most abundant species followed by T. citrinoviride (26.8%) and T. harzianum (23.9%). The ability of Trichoderma species to discolor wood was also examined on sapwood blocks made of the commercially important radiata pine (Pinus radiata). T. pleuroticola caused the greatest discoloration of the wood surface.

Fungi associated with bamboo and their decay capabilities

Abstract Biological deterioration is the most important issue facing the use of bamboo as a bioresource. To identify the fungi responsible for bamboo degradation, isolates were obtained from three decaying bamboo species and evaluated. A total of 16 genera and 18 species of fungi were isolated and identified. The major fungi causing serious damage are Trametes versicolor and Arthrinium arundinis, which caused the largest weight losses in tests, of approximately 21.6% and 17.9%, respectively. This investigation confirms that the natural durability of bamboo in outdoor utilization is low.

Bioremediation of Polycyclic Aromatic Hydrocarbons in Creosote-Contaminated Soil by Peniophora incarnata KUC8836

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are present in products made from creosote, coal tar, and asphalt. When wood pile treated with creosote is placed in soil, PAHs can contaminate it. Creosote has been used for wood preservation in the past and is composed of approximately 85% PAHs and 15% phenolic compounds. PAHs cause harmful effects to humans and the environment because of their carcinogenic and mutagenic properties. White rot fungi can degrade not only lignin, but also recalcitrant organic compounds such as PAHs. Among numerous white rot fungi used in previous studies, four species were selected to degrade PAHs in a liquid medium. From this evaluation of the degradation of PAHs by the four fungal isolates, two species were ultimately selected for the highest rates of removal. Following 2 weeks of incubation with Peniophora incarnata KUC8836, the degradation rates of phenanthrene, fluoranthene, and pyrene were 86.5%, 77.4%, and 82.6%, respectively. Mycoaciella bispora KUC8201 showed the highest degradation rate for anthracene (61.8%). Hence, bioremediation of creosote-contaminated soil with an initial concentration of 229.49 mg kg−1 PAHs was carried out using the two selected fungi because they could simultaneously degrade 13 more PAHs than the comparison species. More importantly, isolates of P. incarnata KUC8836 were discovered as powerful degraders of PAHs by producing laccase and manganese-dependent peroxidase (MnP), with 1.7- and 1.1-fold higher than the comparison species, respectively. Therefore, the white rot fungus may be proposed for the removal of PAHs and xenobiotic compounds in contaminated environments.

Extraction of chromium, copper, and arsenic from CCA-treated wood by using wood vinegar.

In the present study, wood vinegar was used to extract chromium, copper, and arsenic from chromated copper arsenate (CCA)-treated wood. The extraction efficiency for CCA elements was evaluated using various concentrations of wood vinegar, extraction temperatures, and extraction periods. The extraction efficiency for CCA elements increased with increasing the concentration of wood vinegar and the extraction conditions, resulting in maximal removal rate of copper (95.7%), followed by arsenic (92.7%) and chromium (86.3%). Since wood vinegar afforded high levels of copper extraction, its use was extended to copper-based preservative-treated wood, wherein significant extraction of copper up to 97.6% and 95.7% was obtained from alkaline copper quats (ACQ)- and copper azole (CuAz)-treated sawdust, respectively. To the best of our knowledge, this is the first study on the application of wood vinegar for the extraction of metal elements from CCA-treated wood.

Primary and secondary decay fungi on exposed pine tree logs in the forest.

Abstract The successional diversity of basidiomycetous fungi was studied on Korean pine (Pinus koraiensis) and pitch pine (Pinus rigida) logs that were left exposed on the forest floor based on fungal surveys conducted after 18, 42, and 54 months of exposure. A total of 131 basidiomycetous isolates were recovered from the logs and grouped by their cultural morphology. Fungal identification was achieved by a BLAST search of partial nuclear large subunit ribosomal DNA sequences in GenBank. The results of the 18 month survey revealed that the isolation frequency and fungal diversity were higher for pitch pine than Korean pine. The dominant species found on Korean and pitch pine logs during the first survey were Hypochnicium karstenii and Phlebiopsis gigantea, respectively. In the 42 and 54 month surveys, the primary species were replaced by Hypochnicium eichleri, Phanerochaete velutina, Phlebia radiata, Rhizochaete sp., and Trametes versicolor. These results showed that decay fungi have host preference for woody materials that vary according to the species of tree being colonized.

Screening for xylanase and β-xylosidase production from wood-inhabiting Penicillium strains for potential use in biotechnological applications.

Abstract Experiments were performed to find potential sources for enzyme production for the pulp and paper industry and for biological ethanol production by screening the cellulase, xylanase and β-xylosidase activities of 36 species of Penicillium isolated from various wood materials in Korea. Rice straw powder (RiceP), birchwood xylan (BirchX), and beechwood xylan (BeechX) were supplied as individual carbon sources for the Penicillium species. All Penicillium species tested in this study showed little cellulase activity, but some species exhibited remarkably high xylanase and β-xylosidase activities, as determined by a filter paper assay. P. oxalicum showed the greatest xylanase activity on RiceP (158.70 U ml-1). On the other hand, P. brevicompactum produced the highest active β-xylosidase on BirchX (6.25 U ml-1).