Sangwoo Kim

Optimization of cross flow filtration system for Dunaliella tertiolecta and Tetraselmis sp. microalgae harvest

We compared Dunaliella tertiolecta LB999 and Tetraselmis sp. KCTC12236BP harvesting efficiency using cross flow filtration (CFF) method. Filtration membranes with pore size of 0.45 μm and 0.2 μm were selected to determine the efficiency of membrane for harvesting. Cross flow filtration using Dunaliella tertiolecta LB999 with 0.45 μm membrane under transmembrane pressure 0.25 bar was the optimal condition for the laboratory system and the harvesting efficiency was 84.7%.

Microbial production of uracil by an isolated Methylobacterium sp. WJ4 using methanol

In this study, we report the production of uracil from methanol by an isolated methylotrophic bacterium, Methylobacterium sp. WJ4. The use of methanol as alternative carbon feedstock is attractive option in biotechnology. As a feedstock of biotechnological processes, methanol has distinct advantages over methane. This is not only due to physical and chemical considerations, but also to the properties of the pertinent organisms. Besides, with a wide array of biological activities and synthetic accessibility, uracil is considered as privileged structures in drug discovery. Uracil analogues have been applied to treatments of patients with cancer or viral infections. In this respect, it is meaningful to produce uracil using methanol. The effect of process parameters and methanol concentration for uracil production were investigated and optimized. Uracil production was remarkably increased to 5.76mgg cell dry weight-1 in optimized condition. The results were significant for further understanding of methylotrophic bacteria on uracil production.

Production of uracil from methane by a newly isolated Methylomonas sp. SW1

Methane is an abundant, inexpensive one-carbon feedstock and one of the most powerful greenhouse gases. Because it does not compete with food demand, it is considered a promising carbon feedstock for the production of valuable products using methanotrophic bacteria. Here, we isolated a novel methanotrophic bacterium, Methylomonas sp. SW1, from a sewage sample obtained from Wonju City Water Supply Drainage Center, Republic of Korea. The conditions for uracil production by Methylomonas sp. SW1, such as Cu2+ concentration and temperature were investigated and optimized. As a result, Methylomonas sp. SW1 produced uracil from methane as a sole carbon source with a titer of 2.1mg/L in 84h without genetic engineering under the optimized condition. The results in this study demonstrate the feasibility of using Methylomonas sp. SW1 for the production of uracil from methane. This is the first report of uracil production from gas feedstock by methanotrophic bacteria.

Effect of heterologous expression of genes involved in the elongation cycle of fatty acid synthesis on fatty acid production in Saccharomyces cerevisiae

In this study, we aimed to develop recombinant Saccharomyces cerevisiae with increased long-chain fatty acids by expressing essential genes involved in fatty acid synthesis elongation cycle. The relation of β-ketoacyl-ACP synthase II (fabF) from S. cerevisiae YPH500 and 3-oxoacyl-[acyl-carrier-protein] reductase (fabG), 3-hydroxyacyl-thioester dehydratase (FabZ), enoyl-ACP reductase (FabK), and acyl-ACP thioesterase (EC.3.1.2.14) from Streptococcus pyogenes MGAS 10270 regarding fatty acid production was investigated. These genes were separately cloned, and the effects of respective genes on fatty acid production were analyzed. Compared with the wild type S. cerevisiae, fabF recombinant (SGJY01) showed about 1.8-fold enhanced fatty acid production. We also exhibited thermal regulation in the fatty acid composition of SGJY01 changed at lower temperatures. The fabF recombinant and wild-type were cultured at different temperatures (30, 20, and 10°C), resulting the unsaturated fatty acids (C16:1 and C18:1) increased up to 2.4-fold as compared to the wild-type. Of particular interest is that the proportion of unsaturated fatty acids was increased approximately 11.8% at 10°C compared to 30°C, although the proportion in the wild-type remained unchanged.