Isolation of a lager yeast with an increased copy number of theYCK1gene and high fermentation performance

Removal of phosphorus from wastewater by Diutina rugosa BL3: Efficiency and pathway

A novel phosphorus removal yeast BL3 was isolated from an alternating anaerobic/aerobic biofilter and identified as Diutina rugosa by 26S rDNA gene sequence analysis. Yeast BL3 could effectively remove phosphorus from synthetic wastewater containing 2-20 mg/L phosphorus under optimal environmental conditions. The highest phosphorus removal efficiency was above 70% under the conditions of DO 6.86 mg/L, C/P ratios of 60, N/P ratios of 3.3, pH 6.0-9.0, and at 25.0-35.0 °C. The phosphorus distribution in the aqueous solution and different components of yeast BL3 analysis indicated that around 55%-70% and 20%-40% of removed phosphorus were transferred into extracellular polymeric substances (EPS) and yeast cells, respectively. The plausible phosphorus transfer pathway was proposed based on the phosphorus distribution and species analysis, suggesting the important role of EPS as a phosphorus reservoir. These results indicate that yeast BL3 can efficiently remove phosphorus under aerobic conditions without alternating anaerobic/aerobic cycling, and thus has significant potential for practical application in wastewater phosphorus removal.

Engineered Polyploid Yeast Strains Enable Efficient Xylose Utilization and Ethanol Production in Corn Hydrolysates

The reported haploid Saccharomyces cerevisiae strain F106 can utilize xylose for ethanol production. After a series of XR and/or XDH mutations were introduced into F106, the XR-K270R mutant was found to outperform others. The corresponding haploid, diploid, and triploid strains were then constructed and their fermentation performance was compared. Strains F106-KR and the diploid produced an ethanol yield of 0.45 and 0.48 g/g total sugars, respectively, in simulated corn hydrolysates within 36 h. Using non-detoxicated corncob hydrolysate as the substrate, the ethanol yield with the triploid was approximately sevenfold than that of the diploid at 40°C. After a comprehensive evaluation of growth on corn stover hydrolysates pretreated with diluted acid or alkali and different substrate concentrations, ethanol yields of the triploid strain were consistently higher than those of the diploid using acid-pretreatment. These results demonstrate that the yeast chromosomal copy number is positively correlated with increased ethanol production under our experimental conditions.