Isopropanol biosynthesis from crude glycerol using fatty acid precursors via engineered oleaginous yeast Yarrowia lipolytica.

BACKGROUND: Isopropanol is widely used as a biofuel and a disinfectant. Chemical preparation of isopropanol destroys the environment, which makes biological preparation of isopropanol necessary. Previous studies focused on the use of expensive glucose as raw material. Therefore, the microbial cell factory that ferments isopropanol with cheap raw materials will provide a greener way to produce isopropanol. RESULTS: This study converted crude glycerol into isopropanol using Y. lipolytica. As a microbial factory, the active natural lipid and fatty acid synthesis pathway endows Y. lipolytica with high malonyl-CoA production capacity. Acetoacetyl-CoA synthase (nphT7) and isopropanol synthesis genes are integrated into the Y. lipolytica genome. The nphT7 gene uses the accumulated malonyl-CoA to synthesize acetoacetyl-CoA, which increases isopropanol production. After medium optimization, the best glycerol medium was found and resulted in a 4.47-fold increase in isopropanol production. Fermenter cultivation with pure glycerol medium resulted in a maximum isopropanol production of 1.94 g/L. In a crude glycerol fermenter, 1.60 g/L isopropanol was obtained, 82.53% of that achieved with pure glycerol. The engineered Y. lipolytica in this study has the highest isopropanol titer reported. CONCLUSIONS: The engineered Y. lipolytica successfully produced isopropanol by using crude glycerol as a cheap carbon source. This is the first study demonstrating the use of Y. lipolytica as a cell factory to produce isopropanol. In addition, this is also a new attempt to accumulate lipid synthesis precursors to synthesize other useful chemicals by integrating exogenous genes in Y. lipolytica.

Non-Photosynthetic CO2 Utilization to Increase Fatty Acid Production in Yarrowia lipolytica.

Metabolic engineering of non-photosynthetic microorganisms to increase the utilization of CO2 has been focused on as a green strategy to convert CO2 into valuable products such as fatty acids. In this study, a CO2 utilization pathway involving carbonic anhydrase and biotin carboxylase was formed to recycle CO2 in the oleaginous yeast Yarrowia lipolytica, thereby increasing the production of fatty acids. In the recombinant strain in which the CO2 utilization pathway was introduced, the production of fatty acids was 10.7 g/L, which was 1.5-fold higher than that of the wild-type strain. The resulting strain had a 1.4-fold increase in dry cell mass compared to the wild-type strain. In addition, linoleic acid was 47.7% in the fatty acid composition of the final strain, which was increased by 11.6% compared to the wild-type strain. These results can be applied as an essential technology for developing efficient and eco-friendly processes by directly utilizing CO2.

Enhanced CO2 fixation and lipid production of Chlorella vulgaris through the carbonic anhydrase complex.

Photosynthesis of C. vulgaris shows slow growth and low lipid production due to the low solubility of CO2, and it is thus necessary to increase the dissolved inorganic carbon source to solve this problem. In this study, carbonic anhydrase (CA) was fused with dockerin to form a CA complex by cohesion-dockerin interaction. The CA complex was displayed on the surface of C. vulgaris by a cellulose binding module. The CA complex increased activity and stability compared to those of a single enzyme. Additionally, C. vulgaris showed an average of 1.6-fold rapid growth during log phase through the influence of the CA complex. The bicarbonate produced by the CA complex increased the lipid production about 1.7-fold (23.3%), compared to 13.6% for the control group. The present results suggest that the CA complex successfully enhances the CO2 fixation, which should be an essential study for 4th generation biofuels.

The change in regional cerebral oxygen saturation after stellate ganglion block.

BACKGROUND: Stellate ganglion block (SGB) is known to increase blood flow to the innervations area of the stellate ganglion. Near infrared spectroscopy reflects an increased blood volume and allows continuous, non-invasive, and bedside monitoring of regional cerebral oxygen saturation (rSO(2)). We investigated the influence of SGB on bilateral cerebral oxygenation using a near infrared spectroscopy. METHODS: SGB was performed on 30 patients with 1% lidocaine 10 ml using a paratracheal technique at the C6 level and confirmed by the presence of Horner's syndrome. The blood pressure (BP), heart rate (HR) and rSO(2) were measured before SGB and 5, 10, 15 and 20 minutes after SGB. Tympanic temperature of each ear was measured prior to SGB and 20 minutes after SGB. RESULTS: The increments of the rSO(2) on the block side from the baseline were statistically significant at 5, 10, 15 and 20 minutes. The rSO(2) on the non-block side compared with the baseline, however, decreased at 15 and 20 minutes. The difference between the block and the non-block sides was significant at 15 and 20 minutes. The BP at 10, 15 and 20 minutes was increased and the HR was increased at 10 and 15 minutes. CONCLUSIONS: We observed an increment of the rSO(2) on the block side from the baseline; however, the rSO(2) on the non-block side decreased.