Hah Young Yoo

A novel alkaline lipase from Ralstonia with potential application in biodiesel production

With the aim of isolating a biocatalyst able to catalyze biodiesel production from microbial source, Ralstonia sp. CS274 was isolated and a lipase from the strain (RL74) was purified. Molecular weight of RL74 was estimated to be 28,000 Da by SDS-PAGE. The activity was highest at 50-55°C and pH 8.0-9.5 and was stable at pH 7.0-12.0 and up to 45°C. It was resistant to oxidizing and reducing agents and the activity was enhanced by detergents. RL74 was 1,3 specific and K(m) and V(max) for p-nitrophenyl palmitate were 2.73 ± 0.6mM and 101.4 ± 1.9 mM/min mg, respectively. N-terminal amino acid sequence showed partial homology with that of Penicillium lipases. RL74 produced biodiesel more efficiently in palm oil than in soybean oil; and the production was highest at pH 8.0, at 5% methanol and at 20% water content.

Enzymatic fuel cells based on electrodeposited graphite oxide/cobalt hydroxide/chitosan composite–enzymeelectrode

Enzymatic fuel cells (EFCs) use redox enzymes with high electron transfer rates that lead to high power density from bioavailable substrates. However, EFCs are limited by the difficult electrical wiring of the enzymes to the electrode. Therefore, deposition of Co(OH)₂ onto graphite oxide (GO) was improved for efficient wiring of the enzymes. The GO/Co(OH)₂/chitosan composites were electrodeposited for immobilization of glucose oxidase (GOD) or laccase on an Au electrode, respectively. The electrical properties of the bioelectrode according to cyclic voltammetry were improved using GO/Co(OH)₂/chitosan composites. The anode and cathode system was composed of GOD and laccase as biocatalysts and glucose/oxygen as substrates under ambient conditions (pH 7.0 and 25 °C). The EFC using GO/Co(OH)₂/chitosan composites with a mediator delivered a high power density of up to 517±3.3 μW/cm² at 0.46 V and open circuit voltage of 0.60 V. These results provide a promising direction for further development and application of EFCs.

Biodiesel production by enzymatic process using Jatropha oil and waste soybean oil

In this study, non-edible Jatropha oil and postcooking waste soybean oil were utilized for enzymatic biodiesel production. The process was optimized by using a statistical method. In addition, a novel continuous process using co-immobilized Rhizopus oryzae and Candida rugosa lipases was developed. The optimum conditions for the batch process were determined to be a reaction temperature of 45oC, an agitation speed of 250 rpm, 10 wt% of water, and 20% of immobilized lipases. A conversion of about 98% at 4 h could be achieved for biodiesel production using Jatropha oil, while a conversion of about 97% at 4 h was achieved from waste soybean oil. A packed bed reactor charged with co-immobilized lipases was employed for continuous biodiesel production from Jatropha and waste soybean oil. The reactor consisted of a jacketed glass column (ID 25 mm × 130 mm), in which a temperature of 45°C was maintained by water circulation. A maximum conversion of about 80% in 24 h at a flow rate of 0.8 mL/ min was achieved with the continuous process, whereas in the two-stage continuous process, a conversion of about 90% in 72 h was attained at a flow rate of 0.1 mL/min.

Biorefinery of instant noodle waste to biofuels

Instant noodle waste, one of the main residues of the modern food industry, was employed as feedstock to convert to valuable biofuels. After isolation of used oil from the instant noodle waste surface, the starch residue was converted to bioethanol by Saccharomyces cerevisiae K35 with simultaneous saccharification and fermentation (SSF). The maximum ethanol concentration and productivity was 61.1g/l and 1.7 g/lh, respectively. After the optimization of fermentation, ethanol conversion rate of 96.8% was achieved within 36 h. The extracted oil was utilized as feedstock for high quality biodiesel conversion with typical chemical catalysts (KOH and H2SO4). The optimum conversion conditions for these two catalysts were estimated; and the highest biodiesel conversion rates were achieved 98.5% and 97.8%, within 2 and 3h, respectively. The high conversion rates of both bioethanol and biodiesel demonstrate that novel substrate instant noodle waste can be an attractive biorefinery feedstock in the biofuels industry.

An Extremely Alkaline Novel Xylanase from a Newly Isolated Streptomyces Strain Cultivated in Corncob Medium

Streptomyces sp. CS802, recently isolated from Korean soil, produced xylanase in corncob medium. An extracellular xylanase (Xyn802) was purified by a single-step gel filtration and biochemical properties were studied. It showed high activity in extremely alkaline condition with optimum pH at 12.0 and exhibited stability between pH 7.5 and 13.0. It produced xylobiose and xylotriose as the major products from xylan, suggesting its endoxylanase nature. N-terminal amino acid sequences of Xyn802 were ADRNANRD which are significantly different from the reported xylanase. The activity was enhanced by various detergents and a reducing agent and stable in various organic solvents. Xyn802 produced by utilizing corncob, an agro-waste material, might be a novel xylanase based on its peculiar biochemical characteristics, and it can be a suitable candidate for the production of xylooligosaccharides including other useful products.

Lipase from Penicillium camembertii KCCM 11268: Optimization of solid state fermentation and application to biodiesel production

Lipase was produced by Penicillium camembertii KCCM 11268 under solid state fermentation (SSF), and the production process was optimized by using statistical experimental designs. The initial moisture content, cultivation time, inoculum size and concentration of basal medium were considered as the factors of optimum conditions for SSF. P. Camembertii KCCM 11268 was cultivated in SSF using wheat bran as the substrate for lipase production. Under the optimized condition, lipase activity was reached around 7.8 U/ml after eight days fermentation. To partially purify the lipase, ammonium sulfate (80% saturation) was added to the crude lipase solution and concentrated using a diafiltration (VIVAFLOW 50). The concentrated lipase solution from P. Camembertii KCCM 11268 (PCL) was immobilized on silica gel by cross-linking method. Also, PCL was mixed with a commercial lipase solution from Candida rugosa (CRL), and this mixture was co-immobilized on silica gel. The immobilized and co-immobilized lipase activities were 1150.1 and 7924.8 U/g matrix, respectively. Palm oil and methanol were used as substrates and 1mmol of methanol was added every 1.5 h and 2 times during biodiesel production. The reaction was carried out at temperatures of 30, 40, 50, 60 and 70 °C. The maximum biodiesel conversion by co-immobilized lipase was 99% after 5 h at 50 °C.

Co-immobilization of Candida rugosa and Rhyzopus oryzae lipases and biodiesel production

Candida rugosa lipase and Ryzopus oryzae lipase were simultaneously immobilized on silica gel following enzyme pretreatment. The factors affecting the co-immobilization process, such as reaction time and enzyme ratio, were investigated. Biodiesel was then produced by using the co-immobilized enzyme matrix. A batch system was employed with stepwise methanol feeding, and the continuous process involved a packed-bed reactor. Under optimal immobilization conditions, the activity was approximately 16,000 U/g·matrix. When co-immobilized enzyme was used with optimized stepwise methanol feeding, conversion of biodiesel reached about 99% at 3 h and was maintained at a level of over 90% for about 30 reuses.

Phenolic compounds: Strong inhibitors derived from lignocellulosic hydrolysate for 2,3-butanediol production by Enterobacter aerogenes.

Lignocellulosic biomass are attractive feedstocks for 2,3‐butanediol production due to their abundant supply and low price. During the hydrolysis of lignocellulosic biomass, various byproducts are formed and their effects on 2,3‐butanediol production were not sufficiently studied compared to ethanol production. Therefore, the effects of compounds derived from lignocellulosic biomass (weak acids, furan derivatives and phenolics) on the cell growth, the 2,3‐butanediol production and the enzymes activity involved in 2,3‐butanediol production were evaluated using Enterobacter aerogenes ATCC 29007. The phenolic compounds showed the most toxic effects on cell growth, 2,3‐butanediol production and enzyme activity, followed by furan derivatives and weak acids. The significant effects were not observed in the presence of acetic acid and formic acid. Also, feasibility of 2,3‐butanediol production from lignocellulosic biomass was evaluated using Miscanthus as a feedstock. In the fermentation of Miscanthus hydrolysate, 11.00 g/L of 2,3‐butanediol was obtained from 34.62 g/L of reducing sugar. However, 2,3‐butanediol was not produced when the concentration of total phenolic compounds in the hydrolysate increased to more than 1.5 g/L. The present study provides useful information to develop strategies for biological production of 2,3‐butanediol and to establish biorefinery for biochemicals from lignocellulosic biomass.

Kinetic modeling of biodiesel production by mixed immobilized and co-immobilized lipase systems under two pressure conditions

A kinetic model of mixed immobilized lipase (MIL) and co-immobilized lipase (CIL) systems was investigated by calculating the kinetic parameters based on the reaction mechanisms for lipase-catalyzed transesterification of soybean oil and methyl alcohol. The kinetic parameters were assessed under atmospheric and supercritical fluid conditions. Although the CIL system had a higher initial reaction rate, the effect of substrate inhibition by methanol was higher than that in the MIL system. The initial reaction rate of MIL and CIL decreased under atmospheric conditions as the methanol concentration increased. However, the initial reaction rate of MIL and CIL increased until methanol concentration increased to twice that of oil under the supercritical fluid condition. As a result, the inhibition effect by methanol was identified through a kinetic analysis. A simulated model can be used to predict the optimal conditions for biodiesel production under atmospheric and supercritical conditions.

Development of glycerol-utilizing Escherichia coli strain for the production of bioethanol

The production of bioethanol was studied using recombinant Escherichia coli with glycerol as a carbon source. Glycerol is an attractive feedstock for biofuels production since it is generated as a major byproduct in biodiesel industry; therefore, we investigated the conversion of glycerol to bioethanol using E. coli BL21 (DE3) which harbors several genes in ethanol production pathway of Enterobacter aerogenes KCTC 2190. Fermentation was carried out at 34°C for 42h, pH 7.6, using defined production medium. Under optimal conditions, bioethanol production by the recombinant E. coli BL21 (DE3), strain pEB, was two-fold (3.01g/L) greater than that (1.45g/L) by the wild-type counterpart. The results obtained in this study will provide valuable guidelines for engineering bioethanol producers.