Ja Hyun Lee

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.

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.

Production of cephalosporin C using crude glycerol in fed-batch culture of Acremonium chrysogenum M35.

In this study, cephalosporin C production by Acremonium chrysogenum M35 cultured with crude glycerol instead of rice oil and methionine was investigated. The addition of crude glycerol increased cephalosporin C production by 6-fold in shake-flask culture, and also the amount of cysteine. In fed-batch culture without methionine, crude glycerol resulted only in overall improvement in cephalosporin C production (about 700%). In addition, A. chrysogenum M35 became highly differentiated in fed-batch culture with crude glycerol, compared with the differentiation in batch culture. The results presented here suggest that crude glycerol can replace methionine and plant oil as cysteine and carbon sources during cephalosporin C production by A. chrysogenum M35.

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.

Immobilization of acetyl xylan esterase on modified graphite oxide and utilization to peracetic acid production

In the previous work, acetyl xylan esterase (AXE) of Aspergillus ficcum was successfully produced in Pichia pastoris as host. In this study, the recombinant AXE was immobilized on graphite oxide and used for the production of peracetic acid. Immobilization efficiency was enhanced by modifying graphite oxide via surface functionalization. The conditions for enzyme immobilization were also investigated and the optimal conditions were determined as 4℃ of temperature, 24 h of reaction time and pH 7. The activity of immobilized AXE was found to be 62.53 U/g-support. With the immobilized AXE, about 134 mM of peracetic acid was produced under 37℃ of temperature and 30 min of reaction time. Enzyme activity remained at > 50% of the original after 10 production cycles.

Furfural production from hydrolysate of barley straw after dilute sulfuric acid pretreatment

Lignocellulosic biomass contains various fermentable sugars and versatile compounds, and should be isolated selectively. In this study, a two step process for furfural production is suggested. Dilute acid pretreatment, which solubilizes hemicellulose, was performed on barley straw at 110–190 °C temperature with 0.1–2% sulfuric acid for 2–20 min and a liquid portion of the hydrolysate was utilized. Using this hydrolysate, furfural production was conducted. Approximately 140–200 °C temperature induced the hydrolysis and pyrolysis of the hydrolysate. The initial reaction rate was found to be 2.84×10−5 mol/L·sec at 180 °C when reacted for 5min, 48.5% of theoretical furfural production was obtained, and it was faster than the generally used one step furfural production methods. In addition, a high temperature gradient for pre-heating showed improvement of temperature control.

Rapid analysis of barley straw before and after dilute sulfuric acid pretreatment by photoluminescence

The fluorescence intensities (FIs) of raw and pretreated barley straws were measured by fluorescence microscopy, and the difference in the fluorescence intensity of barley straw before and after dilute acid pretreatment was analyzed by investigation of the major compounds of barley straw. The difference in fluorescence intensity was due to the difference in xylan content. Barley straw was pretreated using dilute sulfuric acid at various conditions and the correlation between the fluorescence intensity and glucose yield of barley straw was investigated. The coefficient of determination (R(2)) of the correlation was found to be 72.28%. Also the calibration of fluorescence intensity with the xylan content was performed. In addition, the absorption and emission spectra of the raw and the pretreated barley straw were examined to verify the proposed method. The absorption and emission wave lengths were 550 nm and 665 nm, respectively.

Enhanced electron transfer mediator based on biochar from microalgal sludge for application to bioelectrochemical systems

This study is focused on the utilization of waste microalgal sludge (MS) from microalgal extraction and its potential as an electrode material. The MS was activated under N2 at high temperature for conversion to biochar (MSB). In addition, cobalt (Co; metal hydroxide) and chitosan were used as a mediator for electron transfer by immobilization on MSB (MSB/Co/chitosan). Through analysis of the surface and components of the MSB/Co/chitosan, it was shown that Co and chitosan were properly synthesized with MSB. The enzymatic fuel cell (EFC) system successfully obtained a power density of 3.1 mW cm-2 and a current density of 9.7 mA cm-2. In addition, the glucose biosensors applied with the developed electron transfer mediator showed a sensitivity of 0.488 mA mM-1 cm-2.