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김선기,Joong Hyuck Auh 한국생물공학회 2021 Biotechnology and Bioprocess Engineering Vol.26 No.1
Saccharomyces cerevisiae is a promising candidate for production of organic acids as it is more tolerant to these acids than the prokaryotes. However, the large-scale production of organic acids from lignocellulosic biomass is limited by their accumulation in the growth medium and inability of xylose fermentation by S. cerevisiae. Here we showed that high intracellular spermidine (SPD) contents confers enhanced tolerance to lactic, succinic, and malic acids in S. cerevisiae. Specifically, in the presence of 20 g/L malic acid, the maximum specific growth rate and dry cell weight of a S. cerevisiae with two fold higher SPD content were 40% and 36% higher than those of the control strain. When a xylose assimilation pathway was introduced into an engineered strain with high SPD content, the resulting S. cerevisiae strain exhibited 23~47% higher xylose consumption rate and 6~16% higher ethanol productivity than those of the control strain during the four times of repeated-batch fermentations using a mixture of glucose and xylose as carbon sources. These results suggest that the strain developed in this study would serve as a platform strain for production of organic acids.
Kang Wonseok,Auh Joong-Hyuck 건강기능식품미래포럼 2021 건강기능식품미래포럼 학술지 Vol.1 No.4
Pimpinella brachycarpa (chamnamul) is traditionally used as edible vegetable as well as medicinal plant in Asian regions. In this study, four extracts of Pimpinella brachycarpa leaves were prepared by the supercritical carbon dioxide method under four different conditions (cosolvent pump [CP], basket soaking [BS], CO2-ethanol washing [CE] and CO2-hexane washing [CH]) and the extracts obtained were compared with respects to yield, antioxidant activity and acquisition of active (metabolomic) components. The highest yield (g of dried extract/g of dried leaves) was obtained from the extract prepared by BS condition (5.89%). Antioxidant activity was assayed by contents of phenolic compounds that were measured by gallic acid equivalent (GAE/g extract) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activities. The total phenolic content was highest in the extract by CP and the activity of DPPH radical scavenging was higher in the extracts by BS and CH. However, the scavenging activity of the extracts by CE and CH was more than 10 times higher than that by CP and BS, meaning that CE and CH conditions are suitable for extracting antioxidant compounds. Metabolomic analysis also showed a significantly different profile among the extracts. These results indicate that the supercritical carbon dioxide extraction method prepares the extracts of different properties depending upon the conditions used and thus, provide useful information for the study on separation and identification of active compounds from medicinal plants.