Seung Gon Wi

The potential value of the seaweed Ceylon moss (Gelidium amansii) as an alternative bioenergy resource.

Sea weed (Ceylon moss) possesses comparable bioenergy production potential to that of land plants. Ceylon moss has high content of carbohydrates, typically galactose (23%) and glucose (20%). We have explored the possibility of sodium chlorite in Ceylon moss pretreatment that can ultimately increase the efficiency of enzymatic saccharification. In an acidic medium, chlorite generates ClO(2) molecules that transform lignin into soluble compounds without any significant loss of carbohydrate content and this procedure is widely used as an analytical method for holocellulose determination. Sodium chlorite-pretreated samples resulted in glucose yield up to 70% with contrast of only 5% was obtained from non-pretreated samples. The efficiency of enzymatic hydrolysis is significantly improved by sodium chlorite pretreatment, and thus sodium chlorite pretreatment is potentially a very useful tool in the utilisation of Ceylon moss biomass for ethanol production or bioenergy purposes.

Characterization of anatomical features and silica distribution in rice husk using microscopic and micro-analytical techniques

Abstract Rice husk is a by-product of rice milling process, and a great resource as a raw biomass material for manufacturing value-added composite products. One of the potential applications is to use rice husk as filler for manufacturing lignocellulosic fiber–thermoplastic composites. This study was conducted to examine the silica distribution in rice husk in preparation to use it as reinforcing filler for thermoplastic polymers. Microscopic techniques, such as light microscopy, scanning electron microscopy and field-emission SEM (FE-SEM) were used to observe the surface and internal structure of rice husk. Microscopic examination showed that two main components of husk, lemma and palea consisted of outer epidermis, layers of fibers, vascular bundles, parenchyma cells, and inner epidermis, in sequence from the outer to the inner surface. Histochemical staining showed that epidermal and fiber cell walls were lignified, and the walls of parenchyma and lower epidermal cells were not lignified. The outer epidermal walls were extremely thick, highly convoluted and lignified. The outer surface of both lemma and palea were conspicuously ridged. The energy dispersive X-ray micro-analysis attached to the FE-SEM provided information on the distribution of silica in the husk. Most of the silica was present in the outer epidermal cells, being particularly concentrated in the dome-shaped protrusions. These observations provided valuable background information on the organization of husk tissues and the distribution of silica, which will help optimize processes related to the use of rice husk for making lignocellulosic fiber–thermoplastic composites in our future work.

Alterations in the Photosynthetic Pigments and Antioxidant Machineries of Red Pepper (Capsicum annuum L.) Seedlings from Gamma-Irradiated Seeds

To characterize the stimulatory effects of low-dose gamma radiation on early plant growth, we investigated alterations in the photosynthesis and antioxidant capacity of red pepper (Capsicum annuum L.) seedlings produced from gamma-irradiated seeds. For two cultivars (Yeomyung and Joheung), three irradiation groups (2, 4, and 8 Gy, but not 16 Gy) showed enhanced development, although Fv/Fm, the maximum photochemical efficiency of Photosystem II (PSII), did not differ significantly among any of the four groups. In contrast, values for 1/Fo — 1/Fm, i.e., a measure of functional PSII content, decreased in the irradiated groups of ‘Yeomyung’ but increased in those of ‘Joheung’. Pigment analyses and enzyme activity assays revealed that irradiation altered the compositions of photosynthetic pigments (chlorophylls and carotenoids) as well as the activities of antioxidant enzymes (superoxide dismutase and glutathione reductase). However, these shifts were not directly related to the increase in early growth, although they were cultivar-and developmental stage-dependent In addition, the effects of irradiation on the enzymatic activities measured here were at opposition between the two cultivars.

Ultrastructural changes of cell organelles inArabidopsis stems after gamma irradation

We examined ultrastructural changes of the cell organelles ofArabidopsis stems in response to gamma irradiation. Seedlings treated with 0 to 5 Gy developed normally, while height growth in plants exposed to 50 Gy was significantly inhibited. Based on TEM observations, the chloroplasts were extremely sensitive to such irradiation. In particular, the thylakoids were heavily swollen, some portions of the mitochondria and endoplasmic reticulum were structurally altered, and the plasmalemma had pulled away from the cell wall in places. However, no ultrastructural changes in cell organelles occurred at doses of 0 to 5 Gy.

Bioethanol production from the nutrient stress-induced microalga Chlorella vulgaris by enzymatic hydrolysis and immobilized yeast fermentation.

The microalga Chlorella vulgaris is a potential feedstock for bioenergy due to its rapid growth, carbon dioxide fixation efficiency, and high accumulation of lipids and carbohydrates. In particular, the carbohydrates in microalgae make them a candidate for bioethanol feedstock. In this study, nutrient stress cultivation was employed to enhance the carbohydrate content of C. vulgaris. Nitrogen limitation increased the carbohydrate content to 22.4% from the normal content of 16.0% on dry weight basis. In addition, several pretreatment methods and enzymes were investigated to increase saccharification yields. Bead-beating pretreatment increased hydrolysis by 25% compared with the processes lacking pretreatment. In the enzymatic hydrolysis process, the pectinase enzyme group was superior for releasing fermentable sugars from carbohydrates in microalgae. In particular, pectinase from Aspergillus aculeatus displayed a 79% saccharification yield after 72h at 50°C. Using continuous immobilized yeast fermentation, microalgal hydrolysate was converted into ethanol at a yield of 89%.

Micromorphological characteristics of decayed wood and laccase produced by the brown-rot fungus Coniophora puteana

Microscopic examination showed the cell wall decay pattern produced by the brown-rot fungus Coniophora puteana to be different from the degradation pattern known to be typical for brown-rot fungi. Erosion and thinning of cell walls in patterns considered to be characteristic of white-rot decay were observed. In particular, the fungal strain COP 20242 degraded secondary cell wall layers extensively, and also degraded lignin-rich middle lamellae. Some strains of C. puteana produced soft-rot type cavities in the S2 layer. All strains of C. puteana employed in the present work showed a positive reaction to tannic acid in the Bavendamm test, indicating the production of laccase. Microscopic and enzymatic studies provided evidence to suggest that the wood decay by C. puteana is unique both in terms of micromorphological and enzymatic patterns of cell wall degradation. This is because brown-rot fungi are not generally known to form cavities in the cell walls or to produce lignin-degrading enzymes. These observations suggest that lignin degradation capacity of brown-rot fungi may be greater than previously considered.

Site-directed mutagenesis and CBM engineering of Cel5A (Thermotoga maritima)

In order to make cost-effective bioethanol from dynamic lignocellulosic material, we require potentially acting and stable cellulolytic enzymes. In our investigation, the hyperthermostable endoglucanase Cel5A from Thermotoga maritima was subjected to site-directed mutagenesis and carbohydrate-binding module (CBM) engineering. For this purpose, amino acids around the active-site region were targeted. Results indicated that five single mutants showed a shift in optimal pH from 5 to 5.4. The N147E mutant displayed 10% higher activity than native Cel5A. Domain engineering was performed with fungal and bacterial CBM. In addition, CBM1 from (CBHII) Trichoderma reesei and CBM6 from Clostridium stercorarium xylanase A were fused with Cel5A. Both the CBM-engineered Cel5A showed 14-18-fold higher hydrolytic activity towards Avicel. Immuno-gold labeling assay of engineered enzymes further indicated the relativity that exists between binding ability and activity.

Enhanced enzymatic hydrolysis of rapeseed straw by popping pretreatment for bioethanol production

The objective of this study was to find a pretreatment process that enhances enzymatic conversion of biomass to sugars. Rapeseed straw was pretreated by two processes: a wet process involving wet milling plus a popping treatment, and a dry process involving popping plus dry milling. The effects of the pretreatments were studied both in terms of structural and compositional changes and change in susceptibility to enzymatic hydrolysis. After application of the wet and dry processes, the amounts of cellulose and xylose in the straw were 37-38% and 14-15%, respectively, compared to 31% and 12% in untreated counterparts. In enzymatic hydrolysis performance, the wet process presented the best glucose yield, with a 93.1% conversion, while the dry process yielded 69.6%, and the un-pretreated process yielded <20%. Electron microscopic studies of the straw also showed a relative increase in susceptibility to enzymatic hydrolysis with pretreatment.

Purification and properties of a chitinase from Penicillium sp. LYG 0704

The chitinase producing Penicillium sp. LYG 0704 was procured from soil of the Chonnam National University crop field. The chitinase activity was detected after the first day which increased gradually and reached its maximum after 3 days of cultivation. The chitinase was purified from a culture medium by precipitation with isopropanol and column chromatography with Mono Q and Butyl-Sepharose. The molecular mass of chitinase was estimated to be 47 kDa by SDS-PAGE. Optimal pH and temperature were 5.0 and 40 degrees C, respectively. The N-terminal amino acid sequence of the enzyme was determined to be (1)AGSYRSVAYFVDWAI(15). The fully cloned gene, 1287 bp in size, encoded a single peptide of 429 amino acids. BLAST search of the chitinase gene sequence showed similarity with chitinase of Aspergillus fumigatus Af293 chitinase gene (58%) and A. fumigatus class V chitinase ChiB1 gene (56%).

Conversion of coffee residue waste into bioethanol with using popping pretreatment.

Coffee residue waste (CRW), which is produced after coffee extraction for coffee powder and instant coffee preparation, is a primary industrial waste. In this study, the use of CRW for bioethanol production was evaluated. The carbohydrate content of CRW was analyzed for fermentable sugars such as glucose, galactose, and mannose, which can be fermented by Saccharomyces cerevisiae. Pretreatment at a pressure of 1.47 MPa for 10 min with popping pretreatment was required to increase enzymatic hydrolysis. CRW was well hydrolyzed following popping pretreatment at 1.47 MPa. The enzymatic conversion rate of CRW to fermentable sugars was 85.6%. Ethanol concentration and yield (based on sugar content) following enzymatic hydrolysis after simultaneous saccharification and fermentation were 15.3g/L and 87.2%, respectively.