Biological recovery of phosphorus (BioP-Rec) from wastewater streams using brewer's yeast on pilot-scale

Most recent advances for phosphorus (P) recovery using brewery yeast on laboratory scale were used to scale up to a pilot-scale process (BioP-Rec module) and applied in a full-scale wastewater treatment plant (WWTP). A P balance was established for WWTP Markranstädt according to two thresholds: (1) the economic feasibility threshold for P recovery of 0.05 kg/m3 of free P, and (2) the German Sewage Sludge Ordinance (GSSO) threshold, which demands that all WWTPs with a P content in dry matter (DM) of biosolids of 20 gP/kgDM or higher in the coming years must perform mandatory P recovery. In terms of defined thresholds, return and excess sludges were identified as the most feasible WWTP process streams for P recovery. In a 1 m3 BioP-Rec module a 3 stage process was established. From the P-rich water-phase of the return sludge produced in stage 1, which contained 0.051 kg/m3 of free P, 77.56% was taken up by P-depleted brewer's yeast Saccharomyces pastorianus in 3 h in stage 2. In stage 3, the yeast was concentrated in 1 h to produce yeast sludge as a fertilizer product. We demonstrated a novel pilot-scale process for the production of bio-based P-rich fertilizer.

Chromosomal Aneuploidy Improves the Brewing Characteristics of Sake Yeast

The effect of chromosomal aneuploidy on the brewing characteristics of brewery yeasts has not been studied. Here we report that chromosomal aneuploidy in sake brewery yeast (Saccharomyces cerevisiae) leads to the development of favorable brewing characteristics. We found that pyruvate-underproducing sake yeast, which produces less off-flavor diacetyl, is aneuploid and trisomic for chromosomes XI and XIV. To confirm that this phenotype is due to aneuploidy, we obtained 45 haploids with various chromosomal additions and investigated their brewing profiles. A greater number of chromosomes correlated with a decrease in pyruvate production. Especially, sake yeast haploids with extra chromosomes in addition to chromosome XI produced less pyruvate than euploids. Mitochondrion-related metabolites and intracellular oxygen species in chromosome XI aneuploids were higher than those in euploids, and this effect was canceled in their "petite" strains, suggesting that an increase in chromosomes upregulated mitochondrial activity and decreased pyruvate levels. These findings suggested that an increase in chromosome number, including chromosome XI, in sake yeast haploids leads to pyruvate underproduction through the augmentation of mitochondrial activity. This is the first report proposing that aneuploidy in brewery yeasts improves their brewing profile.IMPORTANCE Chromosomal aneuploidy has not been evaluated in development of sake brewing yeast strains. This study shows the relationship between chromosomal aneuploidy and brewing characteristics of brewery yeast strains. High concentrations of pyruvate during sake storage give rise to α-acetolactate and, in turn, to high concentrations of diacetyl, which is considered an off-flavor. It was demonstrated that pyruvate-underproducing sake yeast is trisomic for chromosome XI and XIV. Furthermore, sake yeast haploids with extra chromosomes produced reduced levels of pyruvate and showed metabolic processes characteristic of increased mitochondrial activity. This novel discovery will enable the selection of favorable brewery yeasts by monitoring the copy numbers of specific chromosomes through a process that does not involve generation/use of genetically modified organisms.