Kyeong Keun Oh

Ethanol production from Saccharina japonica using an optimized extremely low acid pretreatment followed by simultaneous saccharification and fermentation

An extremely low acid (ELA) pretreatment using 0.06% (w/w) sulfuric acid at 170 °C for 15 min was employed to extract non-glucan components from Saccharina japonica, a brown macroalgae. Subsequent simultaneous saccharification and fermentation (SSF) was conducted using Saccharomyces cerevisiae DK 410362 and cellulase (15 FPU/g-glucan) and ß-glucosidase (70 pNPGU/g-glucan). Deionized water was used for making fermentation suspension. After the ELA pretreatment, a glucan content of 29.10% and an enzymatic digestibility of 83.96% was obtained for pretreated S. japonica. These values are 4.2- and 2.4-fold higher, respectively, than those of obtained with untreated S. japonica. In SSF, a bioethanol concentration of 6.65 g/L was obtained, corresponding to a glucose equivalent concentration of 13.01 g/L, which indicated an SSF yield of 67.41% based on the total available glucan of the pretreated S. japonica. The remaining separated liquid hydrolysate, which contains mannitol and alginate-derived oligosaccharides can be applied to other fermentations.

Ethanol production from oil palm trunks treated with aqueous ammonia and cellulase

Oil palm trunks are a possible lignocellulosic source for ethanol production. Low enzymatic digestibility of this type of material (11.9% of the theoretical glucose yield) makes pretreatment necessary. An enzymatic digestibility of 95.4% with insoluble solids recovery of 49.8% was achieved after soaking shredded oil palm trunks in ammonia under optimum conditions (80°C, 1:12 solid-to-liquid ratio, 8h and 7% (w/w) ammonia solution). Treatment with 60 FPU of commercial cellulase (Accellerase 1000) per gram of glucan and fermentation with Saccharomyces cerevisiae D(5)A resulted in an ethanol concentration of 13.3g/L and an ethanol yield of 78.3% (based on the theoretical maximum) after 96 h. These results indicate that oil palm trunks are a biomass feedstock that can be used for bioethanol production.

Behaviors of glucose decomposition during acid-catalyzed hydrothermal hydrolysis of pretreated Gelidium amansii.

Acid-catalyzed hydrothermal hydrolysis is one path to cellulosic glucose and subsequently to its dehydration end products such as hydroxymethyl furfural (HMF), formic acid and levulinic acid. The effect of sugar decomposition not only lowers the yield of fermentable sugars but also forms decomposition products that inhibit subsequent fermentation. The present experiments were conducted with four different acid catalysts (H(2)SO(4), HNO(3), HCl, and H(3)PO(4)) at various acid normalities (0.5-2.1N) in batch reactors at 180-210 °C. From the results, H(2)SO(4) was the most suitable catalyst for glucose production, but glucose decomposition occurred during the hydrolysis. The glucose production was maximized at 160.7 °C, 2.0% (w/v) H(2)SO(4), and 40 min, but resulted in a low glucan yield of 33.05% due to the decomposition reactions, which generated formic acid and levulinic acid. The highest concentration of levulinic acid, 7.82 g/L, was obtained at 181.2 °C, 2.0% (w/v) H(2)SO(4), and 40 min.

A novel bioreactor with an internal adsorbent for integrated fermentation and recovery of prodigiosin-like pigment produced from Serratia sp. KH-95

A novel bioreactor with an internal adsorbent was developed for the simultaneous fermentation and recovery of prodigiosin-like pigment produced from Serratia sp. KH-95 as a model product in one bioreactor. The pigment concentration recovered in the internal adsorbent was 13.1 g l−1, which was 1.8-fold higher than that obtained in a bioreactor with an external adsorbent.

Application of a continuous twin screw-driven process for dilute acid pretreatment of rape straw.

Rape straw, a processing residue generated from the bio-oil industry, was used as a model biomass for application of continuous twin screw-driven dilute acid pretreatment. The screw rotation speed and feeding rate were adjusted to 19.7rpm and 0.5g/min, respectively to maintain a residence time of 7.2min in the reaction zone, respectively. The sulfuric acid concentration was 3.5wt% and the reaction temperature was 165°C. The enzymatic digestibility of the glucan in the pretreated solids was 70.9%. The continuous process routinely gave around 28.8% higher yield for glucan digestibility than did the batch processing method.

Optimization of fermentable sugar production from rape straw through hydrothermal acid pretreatment.

Operational conditions for the hydrolysis of rape straw were optimized using the combined severity index (CS), which combines the effects of time, temperature, and acid concentration into a single parameter. The sugar recovery yield was 77.8% of the theoretical yield at a value of CS=1.3. A maximum concentration of xylose of 7.22 g/L was obtained when the straw was treated for 10 min at a low reaction temperature (150 °C) and high acid concentration (pH 1.17). The pentose-rich hydrolyzate exhibited a low concentration of fermentation-inhibiting compounds. The concept of CS can be conveniently and effectively applied for optimization of pretreatments.

Bioconversion of sawdust into ethanol using dilute sulfuric acid-assisted continuous twin screw-driven reactor pretreatment and fed-batch simultaneous saccharification and fermentation.

Ethanol production from poplar sawdust using sulfuric acid-assisted continuous twin screw-driven reactor (CTSR) pretreatment followed by simultaneous saccharification and fermentation (SSF) was investigated. Pretreatment with high acid concentration increased the cellulose content in the pretreated solid (74.9-76.9% in the range of 4.0-5.5wt.% H(2)SO(4)). The sugar content (XMG; xylan+mannan+galactan) in the treated-solid was 11.1-15.2% and 0.9-5.7% with 0.5wt.% and 7.0wt.%, respectively. The XMG recovery yield of the sample treated with 4.0wt.% H(2)SO(4) at 185°C was maximized at 88.6%. Enzymatic hydrolysis test showed a cellulose digestibility of 67.1%, 70.1%, and 73.6% with 15, 30, and 45FPU/g-cellulose, respectively. In the fed-batch SSF tests with initial enzyme addition, the ethanol yield of each stage almost reached a maximum at 28h, 48h, and 56h, respectively, with yields of 63.9% (16.5g/L), 78.4% (30.1g/L), and 81.7% (39.9g/L), respectively.

Two-stage acid saccharification of fractionated Gelidium amansii minimizing the sugar decomposition.

Two-stage acid hydrolysis was conducted on easy reacting cellulose and resistant reacting cellulose of fractionated Gelidium amansii (f-GA). Acid hydrolysis of f-GA was performed at between 170 and 200 °C for a period of 0-5 min, and an acid concentration of 2-5% (w/v, H2SO4) to determine the optimal conditions for acid hydrolysis. In the first stage of the acid hydrolysis, an optimum glucose yield of 33.7% was obtained at a reaction temperature of 190 °C, an acid concentration of 3.0%, and a reaction time of 3 min. In the second stage, a glucose yield of 34.2%, on the basis the amount of residual cellulose from the f-GA, was obtained at a temperature of 190 °C, a sulfuric acid concentration of 4.0%, and a reaction time 3.7 min. Finally, 68.58% of the cellulose derived from f-GA was converted into glucose through two-stage acid saccharification under aforementioned conditions.

Acid-catalyzed hydrothermal severity on the fractionation of agricultural residues for xylose-rich hydrolyzates

The objective of this work was to investigate the feasibility of acid-catalyzed hydrothermal fractionation for maximum solubilization of the hemicellulosic portion of three agricultural residues. The fractionation conditions converted into combined severity factor (CS) in the range of 1.2-2.9. The highest hemicellulose yield of 87.88% was achieved when barley straw was fractionated at a CS of 2.19. However, the maximum glucose release of 15.29% was achieved for the case of rice straw. The maximum productions of various by-products were observed with the fractionation of rape straw: 0.88 g/L of 5-hydroxymethylfurfural (5-HMF), 2.16 g/L of furfural, 0.44 g/L of levulinic acid, 1.59 g/L of formic acid, and 3.06 g/L of acetic acid. The highest selectivities, a criterion for evaluating the fractionation of 21.55 for fractionated solid and 7.48 for liquid hydrolyzate were obtained from barley straw.

Fractionation and delignification of empty fruit bunches with low reaction severity for high sugar recovery.

Fractionation and delignification of empty fruit bunches (EFB) was conducted in a series of two steps under low reaction severity with the aim of minimizing the neutralization of hydrolyzates. In EFB underwent acid fractionation, the glucan content was increased to 62.4%, at which point 86.9% of the hemicellulosic sugar and 20.5% of the lignin were extracted from the raw EFB. Xylose-rich hydrolyzate, indicating a high selectivity of 17.7 could be separated. Through the consecutive delignification of acid-fractionated EFB using sodium hydroxide, solid residue with a high glucan content (70.4%) and low hemicellulosic sugar content (3.7%) could be obtained, which indicated that 95.9% of the hemicellulosic sugar and 67.5% of the lignin were extracted based on raw EFB. The final pretreated solid residue was converted to glucose through enzyme hydrolysis, which resulted in an enzymatic digestibility of 76.9% was achieved.