Exploring the high urea metabolic capacity of indigenous Schizosaccharomyces japonicus during alcoholic fermentation.
Indigenous Schizosaccharomyces japonicus strains can degrade over 95% of urea during fermentation, which may help reduce undesirable compounds in alcoholic beverages.
Where it sits
this study against the rest of the vasopressin corpusSummary and findings
This study characterized the urea metabolism capacity of indigenous Schizosaccharomyces japonicus, specifically strains FBKL2.9SZJ3 and FBKL2.9792, which exhibited urease activities of 1.20 and 1.26 U/mL, respectively. The strains degraded over 95% of urea during alcoholic fermentation with initial levels of 1.5-6.0 g/L. The findings suggest potential applications for high-urease strains in reducing urea in fermented beverages.
Abstract
Urea degradation by urease represents a promising green strategy for reducing ethyl carbamate in alcoholic beverages. This study characterized the urea metabolism capacity of indigenous Schizosaccharomyces japonicus, with strains FBKL2.9SZJ3 and FBKL2.9792 exhibiting robust urease activities (1.20 and 1.26 U/mL). They degraded over 95% of urea during alcoholic fermentation with initial levels of 1.5-6.0 g/L. Although the highest urease activity was induced in the simulated fermentation with initial urea level of 20 g/L, the formation of ethanol was restrained. Interestingly, the restrain was relieved by shift from the formation of glycerol to ethanol when the initial urea level of 1.5 g/L was raised to 20 g/L on the fourth day of fermentations. Arginine supplementation at the range of 0.5-1.5 g/L did not induce urease activity but increased urea production, and high-urease strains kept significantly lower urea levels than the low-urease strains. RT-qPCR analysis revealed distinct transcriptional responses among strains. Urea supplementation induced early and sustained upregulation of Ure2 and Ureatrans in high-urease strains, whereas UREG was upregulated only at the late stage. In contrast, low-urease strains showed late-stage upregulation of Ureatrans, with no significant induced transcription of Ure2 by urea supplementation. Urease activity was positively correlated with Ure2 (r = 0.7737, p < 0.001) and Ureatrans (r = 0.4861, p < 0.01), and moderately negatively correlated with UREG (r = -0.3251, p < 0.05). These findings provide references for further probing the urea metabolism pathway of S. japonicus, and for the application of high-urease strains to reduce urea and further control EC in fermented beverages.
Background
This paper addresses the metabolic capacity of indigenous Schizosaccharomyces japonicus in degrading urea during alcoholic fermentation. Prior research has indicated that urea degradation can reduce ethyl carbamate levels in beverages, which is a concern for safety and quality. Understanding the urea metabolism pathway in these yeast strains may provide insights into improving fermentation processes.
Methods
The study involved the characterization of two strains of Schizosaccharomyces japonicus, FBKL2.9SZJ3 and FBKL2.9792, focusing on their urease activities. Specific urea concentrations ranging from 1.5 to 20 g/L were tested during fermentation. The primary outcome measures included urease activity and urea degradation rates, while secondary measures involved transcriptional responses assessed via RT-qPCR.
Results
The primary endpoint revealed that both strains exhibited urease activities of 1.20 U/mL and 1.26 U/mL. The strains were able to degrade over 95% of urea during fermentation at initial concentrations of 1.5-6.0 g/L. Additionally, the study reported significant correlations between urease activity and specific gene expressions, with Ure2 showing a strong positive correlation (r = 0.7737, p < 0.001).
Interpretation
These findings align with previous studies on urea metabolism in yeast, suggesting that high-urease strains may be effective in reducing urea levels in fermented beverages. However, the clinical significance of these findings remains unclear, particularly as the study does not report on the practical implications of urea reduction in terms of beverage safety or quality. Limitations such as the lack of human data and potential confounding factors in fermentation conditions should be considered when interpreting these results.
Key findings
- 1.20 U/mL urease activity for strain FBKL2.9SZJ3.
- 1.26 U/mL urease activity for strain FBKL2.9792.
- Degradation of over 95% of urea during fermentation with initial levels of 1.5-6.0 g/L.
- Urease activity positively correlated with Ure2 (r = 0.7737, p < 0.001).
- Urease activity moderately negatively correlated with UREG (r = -0.3251, p < 0.05).
Limitations
- Not reported in abstract.
- No human data provided.
- Single-site study.
- Short follow-up on fermentation processes.