• Korean Chemical Engineering Research
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• v.57 no.1
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• pp.1-4
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• 2019

In this study, an anthracene cross-linker is introduced to enhance the catalytic activity of glucose oxidase (GOx) based catalysts and to increase the amount of enzyme loading. The crosslinked GOx is bonded with the CNT/PEI support using the electrostatic interaction (AC[CNT/PEI/GOx]). Electrochemical evaluations are done to evaluate the performance of this catalyst and the performance of CNT/PEI/GOx catalyst is also measured as a control. According to the measurements, it is confirmed that the amount of loaded GOx increases, while $K_m$ value calculated by Lineweaver-Burk plot shows that AC[CNT/PEI/GOx] ($K_m$ : 0.73 mM) is superior to CNT/PEI/GOx ($K_m$ : 1.71 mM) without cross-linking reaction. Based on these effects, it is demonstrated that the maximum power density of the enzymatic biofuel cell using AC[CNT/PEI/GOx] increases from $21.2{\mu}W/cm^2$ to $57.4{\mu}W/cm^2$.

• Journal of the Korean Wood Science and Technology
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• v.45 no.2
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• pp.232-242
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• 2017

The objective of this study was to examine changes in the porosity and internal structure of wood as it goes through the process of saccharification (extraction of fermentable sugars). This study also examined the use of different drying methods to prepare samples for characterization of internal pores, with particular emphasis on the partially disrupted cell wall. Aspen wood flour samples after dilute acid pretreatment followed by enzymatic hydrolysis were examined for nitrogen adsorption. The resulting isotherms were analyzed for surface area, pore size distribution, and total pore volume. Results showed that freeze drying (with sample pre-freezing) maintains the cell wall structure, allowing for examination of saccharification effects. Acid pretreatment (hemicellulose removal) doubled the surface area and tripled the total volume of pores, which were mostly 10-20 nm wide. Subsequent enzymatic hydrolysis (cellulose removal) caused a 5-fold increase in the surface area and a ~ 11-fold increase in the total volume of pores, which ranged from 5 to 100 nm in width. These results indicate that nitrogen adsorption analysis is a feasible technique to examine the internal pore structure of lignocellulosic residues after saccharification. The information on the pore structure will be useful when considering value-adding options for utilizing the solid waste for biofuel production.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.487-496
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• 2021

Microalgae is one of the promising biodiesel feedstock with high growth rates compared to those of terrestrial oil crops. Despite its numerous advantages, biodiesel production from microalgae needs to reduce energy demand and material costs further to go to commercialization. During solvent extraction of microalgal lipids, lipid-extracted algae (LEA) cell residue is generated as an organic solid waste, about 80-85% of original algal biomass, and requires an appropriate recycling or economic disposal. The resulting LEA still contains significant amount of carbohydrates, proteins, N, P, and other micronutrients. This review will focus on recent advancement in the utilization of LEA as: (i) utilization as nutrients or carbon sources for microalgae and other organisms, (ii) anaerobic digestion to produce biogas or co-fermentation to produce CH₄ and H₂, and (iii) conversion to other forms of biofuel through thermochemical degradation processes. Possible mutual benefits in the integration of microalgae cultivation-biodiesel production-resulting LEA with anaerobic digestion and thermochemical conversion are also discussed.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2023.04a
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• pp.12-12
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• 2023

Plant biomass, or lignocellulose, is one of the most abundant natural resources on earth. Lignocellulosic biomass, such as agricultural and forestry residue, serves as a renewable feedstock for microbial cell factories due to its low price and abundant availability. However, the recalcitrance of lignocellulosic biomass requires a pretreatment process prior to microbial fermentation, from which fermentable sugars including xylose and glucose are generated along with various inhibitory compounds. The presence of furan derivatives, such as 5-hydroxymethyl-2-furaldehyde and 2-furaldehyde (furfural), hampers the microbial conversion of lignocellulosic biomass into value-added commodities. In this study, furfural tolerance was improved by investigating the detoxification mechanism in non-model yeast. The genes encoding aldehyde dehydrogenases were overexpressed to enhance furfural tolerance and resulted in improving cell growth and lipid production that can be converted into biofuel. Taken together, this approach contributes to the understanding of the reducing toxicity mechanism of furfural by the aldehyde dehydrogenases and provides a promising strategy that the use of microorganism as an industrial workhorse to treat efficiently lignocellulosic biomass as sustainable plant derivatives.

• Mycobiology
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• v.42 no.3
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• pp.249-255
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• 2014

We evaluated a more practical and cost-effective immobilization carriers for ethanol production using the yeast Saccharomyces cerevisiae. Three candidate materials-rice hull, rice straw, and sawdust-were tested for their cell-adsorption capacity and operational durability. Derivatizations of rice hull, rice straw, and sawdust with the optimal concentration of 0.5 M of 2-(diethylamino)ethyl chloride hydrochloride (DEAE HCl) resulted in > 95% adsorption of the initial yeast cells at 2 hr for DEAE-rice hull and DEAE-sawdust and in only approximately 80% adsorption for DEAE-rice straw. In addition, DEAE-sawdust was found to be a more practical carrier for immobilizing yeast cells in terms of operational durability in shaking flask cultures with two different speeds of 60 and 150 rpm. Furthermore, the biosorption isotherms of DEAE-rice hull, -rice straw, and -sawdust for yeast cells revealed that the $Q_{max}$ of DEAE-sawdust (82.6 mg/g) was greater than that of DEAE-rice hull and DEAE-rice straw. During the 404-hr of continuous column reactor operation using yeast cells immobilized on DEAE-sawdust, no serious detachment of the yeast cells from the DEAE-sawdust was recorded. Ethanol yield of approximately 3.04 g/L was produced steadily, and glucose was completely converted to ethanol at a yield of 0.375 g-ethanol/g-glucose (73.4% of the theoretical value). Thus, sawdust is a promising practical immobilization carrier for ethanol production, with significance in the production of bioethanol as a biofuel.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.2
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• pp.75-82
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• 2011

Recently the technology of green growth became more important role among the problems of running out of fossil fuels and global warming. To procure a new growth power combined with energy and green growth, a lot of investment for wind power, photovoltaics system, fuel cell and biofuel expanded day by day. Among these, wing power has a merit of a highly economic and no discharge of toxic substance. These days government and industrial companies actively support the development of wind power technology with lots of investment, but domestic related education and equipment still stay in research level when it is compared with foreign advanced countries which lead the wind power technology. Therefore to expand the base of basic skill required in the related industrials and to advance technology, we are in the situation to be needed a development of a new curriculum and educational equipment which is analogous with the actual industrial system. In this paper a development of a new educational equipment for the learning of turbine control is introduced. This educational equipment has been developed for students to get easy understanding for the theory of wind turbine control. And finally to demonstrate the effect of the use of the developed equipments and curriculum a questionnaire carried out.

• Journal of Microbiology and Biotechnology
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• v.25 no.9
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• pp.1547-1554
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• 2015

The potential of microalgae biofuel has not been realized because of the low productivity and high costs associated with the current cultivation systems. In this study, a new low-cost and transparent attachment material was tested for cultivation of a filamentous algal strain, Stigeoclonium sp., isolated from wastewater. Initially, the different materials tested for Stigeoclonium cultivation in untreated wastewater were nylon mesh, polyethylene mesh, polypropylene bundle (PB), polycarbonate plate, and viscose rayon. Among the materials tested, PB led to a firm attachment, high biomass (53.22 g/m², dry cell weight), and total lipid yield (5.8 g/m²) with no perceivable change in FAME profile. The Stigeoclonium-dominated biofilm consisted of bacteria and extracellular polysaccharide, which helped in biofilm formation and for effective wastewater treatment (viz., removal efficiency of total nitrogen and total phosphorus corresponded to ~38% and ~90%, respectively). PB also demonstrated high yields under multilayered cultivation in a single reactor treating wastewater. Hence, this system has several advantages over traditional suspended and attached systems, with possibility of increasing areal productivity three times using Stigeoclonium sp. Therefore, multilayered attached growth algal cultivation systems seem to be the future cultivation model for large-scale biodiesel production and wastewater treatment.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.87-92
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• 2013

Microalgae have been suggested as a promising feedstock for producing biofuel because of their potential of lipid production. In this study, a first principles ODE model for microalgae growth and neutral lipid synthesis proposed by Surisetty et al. (2010) is investigated for the purpose of maximizing the rate of microalgae growth and the amount of neutral lipid. The model has 6 states and 12 parameters and follows the assumption of Droop model which explains the growth as a two-step phenomenon; the uptake of nutrients is first occurred in the cell, and then use of intra-cellular nutrient to support cells growth. In this study, optimal input design using D-optimality criterion is performed to compute the system input profile and sensitivity analysis is also performed to determine which parameters have a negligible effect on the model predictions. Furthermore, model predictive control based on successive linearization is implemented to maximize the amount of neutral lipid contents.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.2
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• pp.137-142
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• 2013

The indiscriminate use of the fossil fuel has caused serious environmental pollutions such as the shortage of energy and global warming. Microalgae have being emphasized as $3^{rd}$ generation biomass which makes the carbon dioxide reduce effectively as well as produces the biofuel. Large scale production of microbial biomass by continuous culture is a quite challenging issue, because off-line optimization strategies of a microbial process utilizing a model-based scheme give rise to many difficult problems. In this paper, the static and simple control method which was able to be applied in time-variant growth environment and large scale of algae culture was studied. The significant disturbances in on-line measurement of cell density were reduced by Savitzky-Golay FIR smoothing filter. Dunaliella salina was cultivated continuously in a flat panel photobioreactor by the on-off control of the turbidostat process.

• Journal of Life Science
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• v.25 no.12
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• pp.1450-1457
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• 2015

To overcome the depletion of fossil fuels and environmental problems in future, the research and production of biofuels have attracted attention largely. Thermophilic microorganisms produce effective and robust enzymes which can hydrolyze plant biomass and survive under harsh bioprocessing conditions. Caldicellulosiruptor bescii, which can degrade unpretreated plants and grow on them, is the one of the best candidates for consolidated bioprocessing (CBP). C. bescii can hydrolyze pectin efficiently as well as the major plant cell wall components, cellulose and hemicelluloses. Many glycosyl hydrolases and carbohydrate lyases with multidomain structure play an important role in plant biomass decomposition. Recently genetic tools for metabolic engineering of C. bescii have developed and bioethanol production from unpretreated biomass is achieved in C. bescii. Here, we review the recent studies for biomass degradation by C. bescii and bioethanol production in C. bescii in order to provide information about metabolic engineering of themophilic bacteria and biofuel development.