Woon-Yong Choi

Enhancement of Lipid Extraction from Marine Microalga, Scenedesmus Associated with High-Pressure Homogenization Process

Marine microalga, Scenedesmus sp., which is known to be suitable for biodiesel production because of its high lipid content, was subjected to the conventional Folch method of lipid extraction combined with high-pressure homogenization pretreatment process at 1200 psi and 35°C. Algal lipid yield was about 24.9% through this process, whereas only 19.8% lipid can be obtained by following a conventional lipid extraction procedure using the solvent, chloroform : methanol (2 : 1, v/v). Present approach requires 30 min process time and a moderate working temperature of 35°C as compared to the conventional extraction method which usually requires >5 hrs and 65°C temperature. It was found that this combined extraction process followed second-order reaction kinetics, which means most of the cellular lipids were extracted during initial periods of extraction, mostly within 30 min. In contrast, during the conventional extraction process, the cellular lipids were slowly and continuously extracted for >5 hrs by following first-order kinetics. Confocal and scanning electron microscopy revealed altered texture of algal biomass pretreated with high-pressure homogenization. These results clearly demonstrate that the Folch method coupled with high-pressure homogenization pretreatment can easily destruct the rigid cell walls of microalgae and release the intact lipids, with minimized extraction time and temperature, both of which are essential for maintaining good quality of the lipids for biodiesel production.

Enhancement of the saccharification yields of Ulva pertusa kjellmann and rape stems by the high-pressure steam pretreatment process

The high-pressure steam process was used to hydrolyze rape stems and Ulva pertusa kjellmann using only water. The biomass was hydrolyzed in a compressed cell at a high temperature and high pressure. The optimal pretreatment conditions were determined to be 180 and 10 bar for 8 min, with 8.5 and 7.4% (w/w) glucose conversion yields, respectively. After the pretreatments, the residues were easily hydrolyzed by treating the enzymes with 1 FPU/mL cellulase, and the 56.8 and 77% (w/w) total cellulose in the results were converted into glucose in 24 h. These results imply that using only water and not any other chemical can efficiently hydrolyze rape stems and Ulva pertusa kjellmann because the high-pressure steam pretreatment process can easily decompose the cellulose structure via XRD analysis, which will result in a high conversion yield with low doses of cellulase. This process was proven to generate a low amount (16.9 ppm) of HMF (hydroxymethylfurfural), which resulted in ethanol production with a 48.7% theoretical maximum conversion yield of glucose. It is believed that this process can be widely used to hydrolyze other agricultural and marine resources for bioethanol production.

Enhancement of Biodiesel Production from Marine Alga, Scenedesmus sp. through In Situ Transesterification Process Associated with Acidic Catalyst

The aim of this study was to increase the yield of biodiesel produced by Scenedesmus sp. through in situ transesterification by optimizing various process parameters. Based on the orthogonal matrix analysis for the acidic catalyst, the effects of the factors decreased in the order of reaction temperature (47.5%) > solvent quantity (26.7%) > reaction time (17.5%) > catalyst amount (8.3%). Based on a Taguchi analysis, the effects of the factors decreased in the order of solvent ratio (34.36%) > catalyst (28.62%) > time (19.72%) > temperature (17.32%). The overall biodiesel production appeared to be better using NaOH as an alkaline catalyst rather than using H2SO4 in an acidic process, at 55.07 ± 2.18% (based on lipid weight) versus 48.41 ± 0.21%. However, in considering the purified biodiesel, it was found that the acidic catalyst was approximately 2.5 times more efficient than the alkaline catalyst under the following optimal conditions: temperature of 70°C (level 2), reaction time of 10 hrs (level 2), catalyst amount of 5% (level 3), and biomass to solvent ratio of 1 : 15 (level 2), respectively. These results clearly demonstrated that the acidic solvent, which combined oil extraction with in situ transesterification, was an effective catalyst for the production of high-quantity, high-quality biodiesel from a Scenedesmus sp.

Bioethanol production using a yeast Pichia stipitis from the hydrolysate of Ulva pertusa Kjellman.

We studied the repeated-batch process for the bioethanol production from the hydrolysate of Ulva pertusa Kjellman using yeast Pichia stipitis, which is able to assimilate C6- and C5-monosaccharides. During 180-hour operations, the repeated-batch process was carried out stably, and the average bioethanol concentration reached 11.9 g/L from about 30 g/L of reducing sugar in the hydrolysate. Meanwhile, the bioethanol yields, based on the reducing sugar and the quantitative TLC analysis, were 0.40 and 0.37, respectively, which corresponded to 78.4% and 72.5% of theoretical value, respectively. Throughout the quantitative process analysis, it was also demonstrated that 39.67 g-bioethanol could be produced from 1 kg of dried Ulva pertusa Kjellman. In this study, we verified that the bioethanol production from the hydrolysate of Ulva pertusa Kjellman was feasible using a yeast Pichia stipitis, particularly during the repeated-batch operation.

Enhancement of Whitening Effects of Lithospermum erythrorhizon Extracts by Ultra High Pressure

In this study, whitening activity of Lithospermum erythrorhizon extracts were investigated according to several extraction processes: water extraction at (WE100) and (WE60), 70% ethyl alcohol extraction (EE) and ultra high pressure extraction (HPE) at 500 MPa for 30 minutes at . The extracts from ultra high pressure extraction showed the highest tyrosinase inhibition and melanogenesis inhibition activities as 52% and 79.5%, respectively, in adding than others extraction processes. HPE extracts also showed the strong reducing power as 3.19 that absorbance at 450 mm. The contents of polyphenol in WE100, we measured as in adding . Extracts have a high total flavonoid contents by HPE as at . We can conclude that better whitening activity of extracts from high pressure extraction was due to high antioxidant activities which could be extracted by higher polyphenol and flavonoid contents in HPE than others.

Ethanol Production from Glycerol using Pachysolen tannophilus in a Surface-aerated Fermentor

We investigated ethanol production from glycerol after screening of the yeast Pachysolen tannophilus ATCC 32691. For yeast to produce ethanol form glycerol, it is important that aeration is finely controlled. Therefore, we attempted to produce ethanol using a surface-aerated fermentor. When 880 ml of YPG medium (1% yeast extract, 2% peptone, 2% glycerol) was used to produce ethanol, the optimal aeration conditions for ethanol production were a surface aeration rate and agitation speed of 500 ml/min and 300 rpm, respectively. In a fed-batch culture, the maximum ethanol production and the maximum ethanol yield from glycerol (Ye/g) was 5.74 g/l and 0.166, respectively, after 90 hr using the surface-aerated fermentor.