The production of livestock and poultry faces major challenges to meet the global demand for meat and dairy products and eggs due to a steady increase in the world’s population and the ban of antibiotics in animal production. This ban has forced animal nutritionists to seek for natural alternatives to antibiotics. In this context, the yeast Saccharomyces cerevisiae has received considerable attention in the last decade. It has been reported that feed supplementation with live yeast cells improve feed efficiency, enhance feed digestibility, increase animal performance, reduce the number of pathogenic bacteria, improve animal health and reduce the negative environmental impacts of livestock production. The current review sheds light on the effects of the use of live S. cerevisiae cells in the diets of nonruminant and pseudo‐ruminant’s animals and the mechanisms by which they exert its effects. This review work revealed that the addition of S. cerevisiae in poultry feed causes a phenomenon called competitive exclusion of pathogenic bacteria capable of causing disease adhere to the yeast surface, and so removing a large amount of harmful micro‐organisms and allowing the Animal defend more effectively, the production of antimicrobial agents, the balancing the gut microbiota and stimulation of host adaptive immune system and improving gut morphological structure, thus these benefits are reflected on the overall poultry health. In addition, in the presence of live S. cerevisiae cells, the immunity of rabbits was improved due to the high number of white blood cell. In addition, apparent digestibility of acid and neutral detergent fibre was improved in horses and rabbits. Saccharomyces cerevisiae in pig diets augment mucosal immunity by increasing IgM and IgA activity against pathogens, enhance intestinal development and function, adsorb mycotoxins, modulate gut microbiota and reduce postweaning diarrhoea.

Pawpaw, banana and watermelon are tropical fruits with short shelf-lives under the prevailing temperatures and humid conditions in tropical countries like Nigeria. Production of wine from these fruits could help reduce the level of post-harvest loss and increase variety of wines. Pawpaw, banana and watermelon were used to produce mixed fruit wines using Saccharomyces cerevisiae isolated from palm wine. Exactly 609 and 406 g each of the fruits in two-mixed and three-mixed fruit fermentation respectively were crushed using laboratory blender, mixed with distilled water (1:1 w/v), and heated for 30 min with subsequent addition of sugar (0.656 kg). The fruit musts were subjected to primary (aerobic) and secondary (anaerobic) fermentation for 4 and 21 days respectively. During fermentation, aliquots were removed from the fermentation tank for analysis. During primary fermentation, consistent increases in alcohol contents (ranging from 0.0 to 15.0 %) and total acidities (ranging from 0.20 to 0.80 %) were observed with gradual decrease in specific gravities (ranging from 1.060 to 0.9800) and pH (ranging from 4.80 to 2.90). Temperature ranged from 27 °C to 29 °C. The alcoholic content of the final wines were 17.50 ± 0.02 % (pawpaw and watermelon), 16.00 ± 0.02 % (pawpaw and banana), 18.50 ± 0.02 % (banana and watermelon wine) and 18.00 ± 0.02 % (pawpaw, banana and watermelon). The alcoholic content of the wines did not differ significantly (p > 0.05). The pH of all the wines were acidic and ranged from 2.5 ± 0.01 to 3.8 ± 0.01 (p > 0.05). The acid concentration (residual and volatile acidity) were within the acceptable limit and ranged from 0.35 ± 0.02 to 0.88 ± 0.01 % (p > 0.05). Sensory evaluation (P > 0.05) rated the wines acceptability as ‘pawpaw and banana wine’ > ‘pawpaw and watermelon’ > ‘pawpaw, watermelon and banana’ > ‘banana and watermelon wine’. This study has shown that acceptable mixed fruit wines could be produced from the fruits with S. cerevisiae from palm wine.

The gene products of the five-membered PRS gene family in Saccharomyces cerevisiae have been shown to exist as three minimal functional entities, Prs1/Prs3, Prs2/Prs5, and Prs4/Prs5, each capable of supporting cell viability. The Prs1/Prs3 heterodimer can be regarded as the most important because its loss causes temperature sensitivity. It has been shown that the GFP signal generated by an integrated GFP-Prs1 construct is lost in the absence of Prs3. In addition to interacting with Prs3, Prs1 also interacts with Slt2, the MAPK of the cell wall integrity (CWI) pathway. Lack of the nonhomologous region (NHR1-1) located centrally in Prs1 abolished the temperature-induced increase in Rlm1 expression. Furthermore, in vitro point mutations generated in PRS1 corresponding to missense mutations associated with human neuropathies or in the divalent cation and/or 5-phosphoribosyl-1(α)-pyrophosphate binding sites also display increased Rlm1 expression at 30 °C and 37 °C and most give rise to caffeine sensitivity. Human PRPS1 cDNA cannot rescue the synthetic lethality of a prs1Δ prs5Δ strain because it lacks sequences corresponding to NHR1-1 of yeast Prs1. The correlation between caffeine sensitivity and increased basal expression of Rlm1 in the altered versions of PRS1 can be extended to their inability to rescue the synthetic lethality of a prs1Δ prs5Δ strain implying that impaired CWI may contribute to the observed loss of viability.

Two of the five unlinked genes theoretically capable of encoding 5-phosphoribosyl-1(α)-pyrophosphate (PRPP) synthetase (Prs) in Saccharomyces cerevisiae, PRS1 and PRS5, contain in-frame insertions which separate the cation- and PRPP-binding sites, diagnostic of Prs polypeptides. The impairment of cell wall integrity (CWI) mitogen-activated protein kinase (MAPK) cascade in strains lacking PRS1 and the synthetic lethality associated with loss of PRS1 and PRS5 imply that these insertions are not gratuitous. Coimmunoprecipitation revealed that Prs1 interacts with the CWI MAPK pathway, only when Slt2 has been phosphorylated by Mkk1/2. Three serine residues identified by phosphoproteome analysis (Ficarro et al 2002) are located in one of the insertions of PRS5 thereby defining Prs5 as one of the 11 triply phosphorylated proteins in yeast. Mutation of these phosphosites compromised the transcriptional readout of one endpoint of the CWI pathway, Rlm1, as well as the expression of the gene encoding the stress-activated 1,3 β-glucan synthase, Fks2, regulated by a second endpoint of the CWI pathway, Swi4/Swi6 (SBF transcription factor). Therefore, the unexpected impairment of the CWI phenotype encountered in yeast strains either mutated or deleted for PRS1 or PRS5 can be explained by disruption of the communication between primary cell metabolism and CWI signalling.

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