• Microbiology and Biotechnology Letters
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• v.42 no.2
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• pp.177-183
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• 2014

Recently, many biofuels and chemicals converted from renewable resources have been introduced into chemical industries. Sargassum fulvellum is a brown macro-algae, which is found on the seashores of Korea and Japan. In this work, the production of total reducing sugar and levulinic acid from S. fulvellum, using dilute-acid catalyzed hydrothermal hydrolysis and statistical methodology, was investigated. As a result, 15.28 g/l total reducing sugar was obtained under the optimized conditions of $160.1^{\circ}C$, 1.0% sulfuric acid, in 20.2 min. Furthermore, 2.65 g/l levulinic acid was obtained at $189.5^{\circ}C$, 2.93% sulfuric acid, in 48.8 min.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.412-418
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• 2023

The surge in the oil prices, increasing global population, climate change, and waste management problems are the major issues which have led to the development of biofuels from lignocellulosic wastes. Cellulosic or second generation (2G) bioethanol is produced from lignocellulosic biomass via pretreatment, hydrolysis, and fermentation. Pretreatment of lignocellulose is of considerable interest due to its influence on the technical, economic and environmental sustainability of cellulosic ethanol production. In this study, furniture waste sawdust was subjected to alkaline peroxide (H₂O₂) for the production of reducing sugars. Sawdust was pretreated at different concentrations from 1-3% H₂O₂ (v/v) loadings at a pH of 11.5 for a residence time of 15-240 min at 50, 75 and 90 ℃. Optimum pretreatment conditions, such as time of reaction, operating temperature, and concentration of H₂O₂, were varied and evaluated on the basis of the amount of total reducing sugars produced. It was found that the changes in the amount of lignin directly affected the yield of reducing sugars. A maximum of 50% reduction in the lignin composition was obtained, which yielded a maximum of 75.3% total reducing sugars yield and 3.76 g/L of glucose. At optimum pretreatment conditions of 2% H₂O₂ loading at 75 ℃ for 150 min, 3.46 g/L glucose concentration with a 69.26% total reducing sugars yield was obtained after 48 hr. of the hydrolysis process. Pretreatment resulted in lowering of crystallinity and distortion of the sawdust after the pretreatment, which was further confirmed by XRD and SEM results.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.561-569
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• 2023

Furfural is a platform chemical that is produced from xylose, one of the hemicellulose components of lignocellulosic biomass. Furfural can be used as an important feedstock for phenolic compounds or biofuels. In this study, we compared and optimized the conditions for producing furfural from xylose in a batch system using two types of catalysts: sulfuric acid, which is commonly used in the furfural production process, and formic acid, which is an environmentally friendly catalyst. We investigated the effects of xylose initial concentration (10 g/L~100 g/L), reaction temperature (140~200 ℃), sulfuric acid catalyst (1~3 wt%), formic acid catalyst (5~10 wt%), and reaction time on the furfural yield. The optimal conditions according to the type of catalyst were as follows. For sulfuric acid catalyst, 3 wt% of catalyst concentration, 50 g/L of xylose initial concentration, 180 ℃ of temperature, and 10min of reaction time resulted in a maximum furfural yield of 59.0%. For formic acid catalyst, 5 wt% of catalyst concentration, 50 g/L of xylose initial concentration, 180 ℃ of temperature, and 150 min of reaction time resulted in a furfural yield of 65.3%.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.132-135
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• 2009

Development of biofuels like ethanol and biodiesel for commercial uses is a recent phenomenon. However, the growth of ethanol and biodiesel has been impressive during the period 2000-2007yr. Globally, production of biodiesel stands around 8.3 billion liters. Europe leads the world in biodiesel production with 80% share of the global biodiesel production total. Today biodiesel fuels have been in commercial use in many countries and recently the world-wide biodiesel market has experienced considerable growth, which is partly due to various tax concession programs and other financial incentives. In Korea, biodiesel has already been used for transportation fuel, but not used for power generation fuel yet. Korean government has a strategy for renewable energy propagation, especially the goal of power generation amount by renewable energy is 3% of total power production by 2012. This paper focuses on the estimation study for effect of using biodiesel as power generation fuel. The study also has the plan to replace the fuel of thermal power plant, gas turbine and distributed power generation system. As the increase of biodiesel fuel, I look forward to environment-friendly power generation and the strategy of Renewable Portfolio Standards(RPS).

• Journal of Microbiology and Biotechnology
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• v.25 no.9
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• pp.1476-1484
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• 2015

Three endoxylanase-encoding genes from the moderately themophilic chemoorganotrophic bacterium Melioribacter roseus were cloned and expressed in Escherichia coli. Genes xyl2091 (Mros_2091) and xyl2495 (Mros_2495) encode GH10 family hydrolases, whereas xyl2090 (Mros_2090) represents the GH30 family. In addition to catalytic domains, Xyl2090 and Xyl2091 contain carbohydrate-binding modules that could facilitate their binding to xylans and Por sorting domains associated with the sorting of proteins from the periplasm to the outer membrane, where they are covalently attached. Recombinant endoxylanase Xyl2495 exhibited a high specific activity of 1,920 U/mg on birchwood xylan at 40℃. It is active at low temperatures, exhibiting more than 30% of the maximal activity even at 0℃. Endoxylanases Xyl2090 and Xyl2091 have lower specific activities but higher temperature optima at 80℃ and 65℃, respectively. Analysis of xylan hydrolysis products revealed that Xyl2090 generates xylo-oligosaccharides longer than xylopentaose. Xylose and xylobiose are the major products of xylan hydrolysis by the recombinant Xyl2091 and Xyl2495. No activity against cellulose was observed for all enzymes. The presence of three xylanases ensures efficient xylan hydrolysis by M. roseus. The highly processive "free" endoxylanase Xyl2495 could hydrolyze xylan under moderate temperatures. Xylan hydrolysis at elevated temperatures could be accomplished by concerted action of two cell-bound xylanases; Xyl2090 that probably degrades xylans to long xylo-oligosaccharides, and Xyl2091 hydrolyzing them to xylose and xylobiose. The new endoxylanases could be useful for saccharification of lignocellulosic biomass in biofuels production, bleaching of paper pulp, and obtaining low molecular weight xylooligosaccharides.

• Ocean and Polar Research
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• v.41 no.4
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• pp.289-309
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• 2019

Marine microalgae have long been used as food additives and feeds for juvenile fish and invertebrates as their nutritional content is beneficial for humans and marine aquaculture species. Recently, they have also been recognized as a promising source for cosmeceutical, nutraceutical, and pharmaceutical products as well as biofuels. Marine microalgae of various species are rich in multiple anti-oxidant phytochemicals and their bioactive components have been employed in cosmetics and dietary supplements. Oil contents in certain groups of marine microalgae are extraordinarily rich and abundant and therefore have been commercialized as omega-3 and omega-6 fatty acid supplements and mass production of microalgae-based biodiesels has been demonstrated by diverse research groups. Numerous natural products from marine microalgae with significant biological activities are reported yearly and this is attributed to their unique adaptive abilities to the great diversity of marine habitats and harsh conditions of marine environments. Previously unknown toxin compounds from red tide-forming dinoflagellates have also been identified which opens up potential applications in the blue biotechnology sector. This review paper provides a brief overview of the biotechnological potentials of Korean marine microalgae. We hope that this review will provide guidance for future marine biotechnology R&D strategies and the various marine microalgae-based industries in Korea.

• Asian Journal of Atmospheric Environment
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• v.7 no.1
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• pp.25-37
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• 2013

Open biomass burning (excluding biofuels) is an important contributor to air pollution in the Asian region. Estimation of emissions from fires, however, has been problematic, primarily because of uncertainty in the size and location of sources and in their temporal and spatial variability. Hence, more comprehensive tools to estimate wildfire emissions and that can characterize their temporal and spatial variability are needed. Furthermore, an emission processing system that can generate speciated, gridded, and temporally allocated emissions is needed to support air-quality modeling studies over Asia. For these reasons, a biomass-burning emissions modeling system based on satellite imagery was developed to better account for the spatial and temporal distributions of emissions. The BlueSky Framework, which was developed by the USDA Forest Service and US EPA, was used to develop the Asian biomass-burning emissions modeling system. The sub-models used for this study were the Fuel Characteristic Classification System (FCCS), CONSUME, and the Emissions Production Model (EPM). Our domain covers not only Asia but also Siberia and part of central Asia to assess the large boreal fires in the region. The MODIS fire products and vegetation map were used in this study. Using the developed modeling system, biomass-burning emissions were estimated during April and July 2008, and the results were compared with previous studies. Our results show good to fair agreement with those of GFEDv3 for most regions, ranging from 9.7 % in East Asia to 52% in Siberia. The SMOKE modeling system was combined with this system to generate three-dimensional model-ready emissions employing the fire-plume rise algorithm. This study suggests a practicable and maintainable methodology for supporting Asian air-quality modeling studies and to help understand the impact of air-pollutant emissions on Asian air quality.

• Journal of Microbiology and Biotechnology
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• v.23 no.3
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• pp.304-312
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• 2013

The thermotolerant methylotrophic yeast Hansenula polymorpha is attracting interest as a potential strain for the production of recombinant proteins and biofuels. However, only limited numbers of genome engineering tools are currently available for H. polymorpha. In the present study, we identified the HpPOL3 gene encoding the catalytic subunit of DNA polymerase ${\delta}$ of H. polymorpha and mutated the sequence encoding conserved amino acid residues that are important for its proofreading 3'${\rightarrow}$5' exonuclease activity. The resulting $HpPOL3^*$ gene encoding the error-prone proofreading-deficient DNA polymerase ${\delta}$ was cloned under a methanol oxidase promoter to construct the mutator plasmid pHIF8, which also contains additional elements for site-specific chromosomal integration, selection, and excision. In a H. polymorpha mutator strain chromosomally integrated with pHIF8, a $URA3^-$ mutant resistant to 5-fluoroorotic acid was generated at a 50-fold higher frequency than in the wild-type strain, due to the dominant negative expression of $HpPOL3^*$. Moreover, after obtaining the desired mutant, the mutator allele was readily removed from the chromosome by homologous recombination to avoid the uncontrolled accumulation of additional mutations. Our mutator system, which depends on the accumulation of random mutations that are incorporated during DNA replication, will be useful to generate strains with mutant phenotypes, especially those related to unknown or multiple genes on the chromosome.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.171-178
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• 2016

Extensive efforts from all over the world have been made to solve energy problems, such as high oil prices, global warning due to the depletion of oil. Among them, biofuel has been drawing attention as a clean energy, which can replace fossil fuels. However, conventional biofuels were often converted from eatable biomass such as sugar cane, corn and soy which should be replaced with uneatable biomass. In this study, a techno-economical evaluation of the gasification of biomass waste with mixed alcohol synthesis process was performed. Considering available domestic biomass wastes, a 2000 ton/day conversion plant were assumed to produce 533000 L/day ethanol. Also, financial data from previous studies were evaluated and used and economical sensitivities with various operation conditions were established. Economic analysis were conducted by the payback period and internal rate of return (IRR) and net present value (NPV). Sensitivity analyses of raw material costs, initial investment, the major process cost, ethanol price changes and operating costs were all performed.

• Journal of Microbiology and Biotechnology
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• v.31 no.7
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• pp.1035-1043
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• 2021

Although engineered Saccharomyces cerevisiae fermenting cellobiose is useful for the production of biofuels from cellulosic biomass, cellodextrin accumulation is one of the main problems reducing ethanol yield and productivity in cellobiose fermentation with S. cerevisiae expressing cellodextrin transporter (CDT) and intracellular β-glucosidase (GH1-1). In this study, we investigated the reason for the cellodextrin accumulation and how to alleviate its formation during cellobiose fermentation using engineered S. cerevisiae fermenting cellobiose. From the series of cellobiose fermentation using S. cerevisiae expressing only GH1-1 under several culture conditions, it was discovered that small amounts of GH1-1 were secreted and cellodextrin was generated through trans-glycosylation activity of the secreted GH1-1. As GH1-1 does not have a secretion signal peptide, non-conventional protein secretion might facilitate the secretion of GH1-1. In cellobiose fermentations with S. cerevisiae expressing only GH1-1, knockout of TLG2 gene involved in non-conventional protein secretion pathway significantly delayed cellodextrin formation by reducing the secretion of GH1-1 by more than 50%. However, in cellobiose fermentations with S. cerevisiae expressing both GH1-1 and CDT-1, TLG2 knockout did not show a significant effect on cellodextrin formation, although secretion of GH1-1 was reduced by more than 40%. These results suggest that the development of new intracellular β-glucosidase, not influenced by non-conventional protein secretion, is required for better cellobiose fermentation performances of engineered S. cerevisiae fermenting cellobiose.