Extra copy of the mitochondrial cytochrome-c peroxidase gene confers a pyruvate-underproducing characteristic of sake yeast through respiratory metabolism.

The mechanism of pyruvate-underproduction of aneuploid sake yeast was investigated in this study. In our previous report, we revealed that an increase in chromosome XI decreases pyruvate productivity of sake yeast. In this report, we found that increased copy number of CCP1, which is located on chromosome XI and encodes cytochrome-c peroxidase, decreased the pyruvate productivity of sake yeasts. Introducing an extra copy of CCP1 activated respiratory metabolism governed by Hap4 and increased reactive oxygen species. Therefore, it was concluded that increased copy number of CCP1 on chromosome XI activated respiratory metabolism and decreased pyruvate levels in an aneuploid sake yeast. This is the first report that describes a mechanism underlying the improvement of brewery yeast by chromosomal aneuploidy.

Chemical and Bacterial Components in Sake and Sake Production Process.

Together with the worldwide Washoku (traditional Japanese foods and drinks) boom, interest in sake, a traditional Japanese alcoholic drink, is increasing around the world. There are few scientific analyses and studies on the production of sake or the final product itself. We show the diversity of bacterial contaminants during sake production and investigated the effects of different ingredients on sake (for example, amino acids). The koji mold Aspergillus oryzae converts rice starch into sugars, and then, the sake yeast Saccharomyces cerevisiae converts the sugars to ethanol. Comparative studies of the bacterial flora of different sakes have shown that various bacterial species are detected, but that there are few frequently detected bacteria. In addition, the bacterial flora does not vary much during the process of sake brewing, after the koji (steamed rice covered with koji mold) and moto (fermentation starter) are mixed, suggesting that most bacteria contaminate the sake during the process of koji and moto production. Thus, there is the possibility that the contaminating bacteria may grow due to a relationship with the koji mold and/or the sake yeast. The flavor, taste, and quality of sakes differ, even between the same brands of sakes, which may be attributed to variations in the contaminating bacteria during sake production.

Pharyngocutaneous fistula caused by dried 'Kombu' (edible seaweed) after total laryngectomy.

The most common early complication after total laryngectomy is pharyngocutaneous fistula (PCF). However, there are no reports of PCF after total laryngectomy caused by 'Kombu' (edible seaweed) as a foreign body in the digestive tract. A 68-year-old Japanese man had undergone total laryngectomy 5 years previously. He presented with PCF, neck swelling and pain. Video endoscopy showed that a dark green foreign body obstructed the digestive tract. PCF was successfully treated via emergency surgery comprising abscess drainage, foreign body removal and fistula closure. The foreign body was kombu. Clinicians who perform total laryngectomy should know the potential dangers of consuming hygroscopic food items that can cause bolus obstruction of the upper digestive tract and pharyngeal abscess and perforation.

Methionine and Glycine Stabilize Mitochondrial Activity in Sake Yeast During Ethanol Fermentation.

Addition of amino acids to fermentation media affects the growth and brewing profiles of yeast. In addition, retaining mitochondrial activity during fermentation is critical for the fermentation profiles of brewer's yeasts. However, a concrete mechanism linking amino acids in fermentation media with mitochondrial activity during fermentation of brewer's yeasts is yet unknown. Here, we report that amino acids in fermentation media, especially methionine (Met) and glycine (Gly), stabilize mitochondrial activity during fermentation of sake yeast. By utilizing atg32△ mutant sake yeast, which shows deteriorated mitochondrial activity, we screened candidate amino acids that strengthened the mitochondrial activity of sake yeast during fermentation. We identified Met and Gly as candidate amino acids that fortify mitochondrial activity in sake yeast during fermentation. To confirm this biochemically, we measured reactive oxygen species (ROS) levels in sake yeast fermented with Met and Gly. Yeast cells supplemented with Met and Gly retained high ROS levels relative to the non-supplemented sake yeast. Moreover, Met-supplemented cells showed a metabolome distinct from that of non-supplemented cells. These results indicate that specific amino acids such as Met and Gly stabilize the mitochondrial activity of sake yeast during fermentation and thus manipulate brewing profiles of yeast.