No description available.

No description available.

No description available.

No description available.

No description available.

The present study was initiated with the purpose of determining and comparing the effect of gamma radiation on the capacity of yeast cells to grow and sporulate. Using a new technique by which irradiated and non-irradiated yeast cells could be scored directly, it was found that sporulating yeast cells were more sensitive to radiation than growing cells, and that the inactivation of the capacity of an irradiated yeast cell to sporulate did not affect its ability to grow. Observations on irradiated sporulating cells indicated that spore-formation and reduction division of the nucleus, are closely allied phenomena. A short discussion of a probable mechanism of action of gamma radiation on sporulating yeast is included, together with suggestions for future research. / Thesis / Master of Science (MS)

No description available.

The nutritional value of novel yeast products were evaluated for warmwater fish species. A yeast co-product (yeast protein concentrate unrefined (YPCU)) obtained from a bio-ethanol process using wheat was tested using iso-nitrogenous (38% crude protein) and iso-lipidic (8%) diets for juvenile mirror carp (Cyprinus carpio). The fishmeal (FM) protein component of a basal diet was replaced by (YPCU) at 7.5, 15, 20, and 50% of total dietary protein. After an 8 week feeding trial, all fish fed YPCU yielded better growth performance than the control fed fish, with diets containing 15% and 20% YPCU being optimal. Whole body composition was unaffected by dietary treatment, however, ash levels were elevated in fish fed >15% YPCU. Hepatic alanine amino transferase (ALAT) and aspartate amino transferase (ASAT) were measured as bio-indicators of liver function in carp. Only ASAT activity was significantly lower for carp fed 20% and 50% YPCU. Additionally, histological assessment of liver and intestinal tissues gave no indication of impairment, but high YPCU inclusion (>15%) elevated the number of goblet cells present in the posterior intestine. Molecular microbiological analysis using DGGE revealed no definitive changes in intestinal microbial communities. In a second study, bio-ethanol yeast (refined YPCR and unrefined YPCU) and dried distillers grain with solubles (DDGS) a co-product of the bio-fuel process and distillery yeast from potable alcohol (whisky) production (YPCPA) were evaluated as before for carp. FM was replaced with 30% of YPCU, YPCR and YPCPA and 15, or 30 % DDGS with a combination of 10% YPCR. Weight gain, and Apparent Net Protein Utilization (ANPU%) were higher in fish fed YPCU 30%, equivalent for fish fed FM, YPCR 30%,DDGS 15% and DDGS 30%, and lower in fish fed YPCPA 30% diets. Feed conversion ratio was significantly increased in carp fed YPCU 30% and decreased for carp fed DDGS 30% and YPC PA 30% compared with the control group. A significant improvement of net mineral retention was seen for carp feed the yeast supplementation diets compared to the fishmeal control group. The YPCU 30% diet produced the highest mineral retention in fish fed yeasts and the YPCPA 30% gave lowest retention. The microvilli density of the intestinal tract decreased for carp fed YPCR 30%, but microvilli length significantly increased in fish fed YPCU 30% compared with other groups, thus indicating changes in gut integrity. In the third study, four diets were formulated to replace 0, 10, 20 and 30% of the fishmeal with refined yeast protein concentrate (YPCR) for Nile tilapia (O. niloticus) of mean weight 12.39g. Growth performance and feed efficiency were not affected with up to 20% replacement with YPCR. There were no obvious changes in the liver structure, but high yeast inclusion showed higher numbers of intestinal goblet cells with increasing YPCR dietary inclusion suggesting enhanced intestinal integrity. Microvilli density and length was significantly (P = 0.025) improved with up to 10% and 30% YPCR inclusion in comparison to other dietary treatments. It was generally concluded that YPC co-products were effectively viable for both juvenile carp and tilapia offering an option for partial fish meal replacement.

Modified atmosphere packaging storage combines an atmosphere of higher carbon dioxide and lower oxygen levels than air, with chilling temperatures to extend shelf-life of fresh fruits. In three modified atmosphere packaging storage trials, blueberries were packaged in film bags with different gas permeabilities, and stored at about 4°C. Storage of blueberries in packages of a film with intermediate gas permeability produced an aerobic atmosphere and a relatively low carbon dioxide level, resulting in rapid growth of yeast and molds on blueberries. Packaging blueberries in a film with very low gas permeability created a high carbon dioxide almost anaerobic atmosphere, which successfully inhibited yeast and mold growth on blueberries for up to eight weeks. The possibility of yeast inhibition by antifungal compounds accumulated in blueberries stored under modified atmosphere packaging conditions was investigated by using the disk diffusion assay. The results of these assays showed the absence of antifungal activity against two Rhodotorula species, a Zygosaccharomyces species, a Cryptococcus species, a Debaryomyces species, and indicated that the inhibition of yeast growth was due to low temperature, high carbon dioxide level and anaerobic conditions. The effects of temperature and atmosphere composition were investigated by using natural flora of blueberry juice and two yeast isolates grown in sterilized juice. At 21°C, yeast growth was slow in the presence of carbon dioxide and absence of oxygen. At low temperature, yeast growth was slow in the presence of oxygen, but was inhibited in the anaerobic, high carbon dioxide environment. It is proposed that the micro-aerobic environment of modified atmosphere packaging storage might have allowed slow desaturation of yeast membrane fatty acids which enabled yeasts to maintain membrane fluidity and function at low .temperature. Furthermore, yeast growth during storage of modified atmosphere packaged blueberries may be affected by low temperature and high carbon dioxide conditions. / Land and Food Systems, Faculty of / Graduate

Indiana University-Purdue University Indianapolis (IUPUI) / Two important nutrient sensing and regulatory pathways, the general amino acid control (GAAC) and the target of rapamycin (TOR), participate in the control of yeast growth and metabolism in response to changes in nutrient availability. Starvation for amino acids activates the GAAC through Gcn2p phosphorylation of the translation initiation factor eIF2 and preferential translation of GCN4, a transcription activator. TOR senses nitrogen availability and regulates transcription factors, such as Gln3p. We used microarray analyses to address the integration of the GAAC and TOR pathways in directing the yeast transcriptome during amino acid starvation and rapamycin treatment. We found that the GAAC is a major effector of the TOR pathway, with Gcn4p and Gln3p each inducing a similar number of genes during rapamycin treatment. While Gcn4p activates a common core of 57 genes, the GAAC directs significant variations in the transcriptome during different stresses. In addition to inducing amino acid biosynthetic genes, Gcn4p activates genes required for assimilation of secondary nitrogen sources, such as -amino-butyric acid (GABA). Gcn2p activation upon shifting to secondary nitrogen sources is suggested to occur by means of a dual mechanism. First, Gcn2p is induced by the release of TOR repression through a mechanism involving Sit4p protein phosphatase. Second, this eIF2 kinase is activated by select uncharged tRNAs, which were shown to accumulate during the shift to GABA medium. This study highlights the mechanisms by which the GAAC and TOR pathways are integrated to recognize changing nitrogen availability and direct the transcriptome for optimal growth adaptation.