Genome-edited Saccharomyces cerevisiae strains for improving quality, safety, and flavor of fermented foods.

While Cas9-based genome editing enabled precise and sophisticated genetic perturbations in conventional and non-conventional yeast strains, its applications for food fermentations have been extremely limited. In order to improve quality and flavor of various yeast-fermented foods, we isolated and engineered a diploid or polyploid Saccharomyces cerevisiae strain (N1) which exhibits robust sugar fermentation, strong acid tolerance, and rapid gas production from Korean Nuruk. First, RGT2 and SNF3 coding for glucose sensors were deleted to increase respiration. A bread dough fermented with the N1ΔRGT2ΔSNF3 strain showed an 18% increased volume due to higher carbon dioxide production. Second, ASP3 coding for asparaginase was overexpressed and URE2 coding for a transcriptional factor of nitrogen catabolite repression (NCR) was deleted to increase asparagine consumption. When the N1ΔURE2::PGPD-ASP3 strain was applied to a potato dough, asparagine was rapidly depleted in the dough, resulting in potato chips with negligible amounts of acrylamide. Third, the N1ΔURE2 strain was utilized to increase levels of the amino acids which provide a savory taste during rice wine fermentation. The above genome-edited yeast strains contain no heterologous DNA. As such, they can be used to improve fermented foods with no subjection to GM regulation.

Image-Guided Laparoscopic Surgical Tool (IGLaST) Based on the Optical Frequency Domain Imaging (OFDI) to Prevent Bleeding.

We present an image-guided laparoscopic surgical tool (IGLaST) to prevent bleeding. By applying optical frequency domain imaging (OFDI) to a specially designed laparoscopic surgical tool, the inside of fatty tissue can be observed before a resection, and the presence and size of blood vessels can be recognized. The optical sensing module on the IGLaST head has a diameter of less than 390 µm and is moved back and forth by a linear servo actuator in the IGLaST body. We proved the feasibility of IGLaST by in vivo imaging inside the fatty tissue of a porcine model. A blood vessel with a diameter of about 2.2 mm was clearly observed. Our proposed scheme can contribute to safe surgery without bleeding by monitoring vessels inside the tissue and can be further expanded to detect invisible nerves of the laparoscopic thyroid during prostate gland surgery.