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Biomedical subjects

D A Abbott

Publications and source records attributed to D A Abbott.

7 recordsLinked to original sources
PubMed2005

The importance of aeration strategy in fuel alcohol fermentations contaminated with Dekkera/Brettanomyces yeasts.

Whole corn mash fermentations infected with industrially-isolated Brettanomyces yeasts were not affected even when viable Brettanomyces yeasts out-numbered Saccharomyces yeasts tenfold at the onset of fermentation. Therefore, aeration, a parameter that is pivotal to the physiology of Dekkera/Brettanomyces yeasts, was investigated in mixed culture fermentations. Results suggest that aeration strategy plays a significant role in Dekkera/Brettanomyces-mediated inhibition of fuel alcohol fermentations. Although growth of Saccharomyces cerevisiae was not impeded, mixed culture fermentations aerated at rates of > or =20 ml air l(-1) mash min(-1) showed decreased ethanol yields and an accumulation of acetic acid. The importance of aeration was examined further in combination with organic acid(s). Growth of Saccharomyces occurred more rapidly than growth of Brettanomyces yeasts in all conditions. The combination of 0.075% (w/v) acetic acid and contamination with Brettanomyces TK 1404W did not negatively impact the final ethanol yield under fermentative conditions. Aeration, however, did prove to be detrimental to final ethanol yields. With the inclusion of aeration in the control condition (no organic acid stress) and in each fermentation containing organic acid(s), the final ethanol yields were decreased. It was therefore concluded that aeration strategy is the key parameter in regards to the negative effects observed in fuel alcohol fermentations infected with Dekkera/Brettanomyces yeasts.

Acetic Acid↗
PubMed2004

Growth rates of Dekkera/Brettanomyces yeasts hinder their ability to compete with Saccharomyces cerevisiae in batch corn mash fermentations.

Growth rates determined by linear regression analysis revealed that Saccharomyces cerevisiae consistently grew more rapidly than Brettanomyces yeasts under a wide array of batch fermentative conditions, including acetic acid stress, in normal gravity (ca. 20 degrees Plato) mashes made from ground corn. Brettanomyces yeasts only grew more rapidly than S. cerevisiae when acetic acid concentrations were elevated to industrially irrelevant levels (>0.45%, w/v). Furthermore, the three Brettanomyces isolates used in this study failed to produce significant quantities of acetic acid under pure culture fermentative conditions. In fact, the small amounts of acetic acid which accumulated in pure culture fermentations of whole corn mash were below the concentration required to inhibit the growth and metabolism of S. cerevisiae. Acetic acid concentrations in pure culture Brettanomyces fermentations exceeded 0.05% (w/v) only in media containing low levels of glucose (<4%, w/v) or when aeration rates were elevated to at least 0.03 vol. air vol.-1 mash min-1. Consequently, it was concluded that Brettanomyces yeasts would not be capable of competing with S. cerevisiae in industrial batch fermentations of whole corn mash based solely on growth rates, nor would they be capable of producing inhibitory concentrations of acetic acid in such fermentations.

Acetic Acid↗
PubMed1997

The influence of a big brothers program on the adjustment of boys in single-parent families.

This study is an evaluation of the self-competence, academic performance, behavioral problems, and parent-child relations of boys who had been raised in single-parent families headed by their mothers and who had weekly contact with an adult friend or companion through a midwestern affiliate of the Big Brothers/Big Sisters of America. Results indicated that participation in such a program was not related to changes in the areas investigated. These findings are not consistent with the social support literature suggesting that an adult companion or friend may benefit children in single-parent families. Further study with a larger sample, over a longer time frame, is recommended.

Achievement↗
PubMed1992

Self-concept and sociometric outcomes: a comparison of only children and sibling children from urban and rural areas in the People's Republic of China.

We investigated differences in self-concept between 360 only children and 555 sibling children in the sixth grade of three urban schools and three rural schools in the People's Republic of China. Peer perceptions and teacher perceptions were also collected using sociometric measures. Self-concept was determined by the Self-Perception Profile for Children (Harter, 1985). Comparisons of sibling children and only children showed no differences on self-concept; however, urban residents had higher self-concept scores than children from rural areas, and boys scored higher than girls. No significant interaction effects between sibling status, gender, and residence were found.

Adolescent↗
PubMed1985

Bile acids. LXXII. High-performance liquid chromatographic analysis of bile acid coenzyme A derivatives.

The mobilities of coenzyme A and coenzyme A derivatives of cholate, chenodeoxycholate, deoxycholate, lithocholate, and their 5 alpha analogs were studied in reversed-phase high-performance liquid chromatography. With a C18 Radial-PAK A cartridge (10-micron particles) and a solvent mixture of 2-propanol/10 mM phosphate buffer (pH 7.0, 140:360), separation of the chenodeoxycholyl and deoxycholyl coenzyme A derivatives was not observed. An increase in ionic strength of the buffer to 50 mM afforded separation, which was markedly augmented with a C18 Radial-PAK A cartridge with 5-micron particles. Lowering the pH of the buffer to 5.5 did not materially change the separations regardless of the ionic strength. Quantitation was carried out to a lower level of 8.5 X 10(-12) mol.

Acyl Coenzyme A↗