An in vitro continuous culture rumen fermentation experiment was conducted to evaluate digestibility of annual ryegrass either fed alone or annual ryegrass supplemented with hay, corn, or soybean hulls. Nutrient disappearance of feedstuffs offered were not different (P > 0.05) as a percentage of the diet however there were differences (P < 0.05) in amounts of individual nutrients digested for each treatment. Ammonia-N concentrations of culture samples were less (P < 0.05) for vessels fed corn as a supplement however there was no difference (P > 0.05) among vessels fed either ryegrass alone or supplemented with hay or soybean hulls. This may indicate a more efficient use of available nutrients from annual ryegrass when corn was supplemented.

No description available.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 104-114).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.) in Oceanography--University of Maine, 2008. / Includes vita. Includes bibliographical references (leaves 156-166).

No description available.

Precise control over microbial cell growth conditions could enable detection of minute phenotypic changes, which would improve our understanding of how genotypes are shaped by adaptive selection. Although automated cell- culture systems such as bioreactors offer strict control over liquid culture conditions, they often do not scale to high-throughput or require cumbersome redesign to alter growth conditions. I report the design and validation of eVOLVER, a scalable DIY framework that can be configured to carry out high- throughput growth experiments in molecular evolution, systems biology, and microbiology. I perform high-throughput evolution of yeast across systematically varied population density niches to show how eVOLVER can precisely characterize adaptive niches. I describe growth selection using time-varying temperature programs on a genome-wide yeast knockout library to identify strains with altered sensitivity to changes in temperature magnitude or frequency. Inspired by large-scale integration of electronics and microfluidics, I also demonstrate millifluidic multiplexing modules that enable multiplexed media routing, cleaning, vial-to-vial transfers and automated yeast mating.

Submitted in fulfilment of the requirements of the Degree of Master of Technology: Biotechnology, Durban University of Technology, 2001. / Kluyveromyces sp. have adapted to existence in milk due to the evolution of permeabilisation and hydrolytic systems that allow the utilisation of lactose, the sugar most abundant in milk. Lactose hydrolysis, to equimolar units of glucose and galactose, is facilitated by a glycoside hydrolase, i.e., β-galactosidase (EC 3.2.1.23). The versatility of this enzyme allows its application in numerous industrial processes, amongst the most significant of which, is its role in the alleviation of lactose intolerance, one of the most prevalent digestive ailments, globally. In this study, β-galactosidase production by Kluyveromyces lactis UOFS y-0939 was initially optimised in shake flask culture with lactose as the sole carbon source, and thereafter, production was scaled up to batch, fedbatch and continuous culture. Shake flask studies revealed optimum conditions of 30°C, pH 7 and a 10% inoculum ratio, to be most favourable for β-galactosidase synthesis, producing a maximum of 0.35 ± 0.05 U.ml-1 when cell lysates were prepared by ultrasonication with glass beads. Batch cultivation in 28.2 and 40 g.L-1 lactose revealed that elevated levels of the carbon source was not inhibitory to β-galactosidase production, as maximum enzyme activities of 1.58 and 4.08 U.ml-1, respectively, were achieved. Cell lysates prepared by ultrasonication and homogenisation were compared and homogenised cell lysates were more than 3.5 fold higher that those prepared by ultrasonication, proving homogenisation to be the superior method for cell disruption. The lactose feed rate of 4 g.L-1.h-1 in fed-batch culture operated at ± 20.4% DO, appeared to be inhibitory to biomass production, as indicated by the lower biomass productivity in fed-batch (0.82 g.L-1.h-1) than batch culture (1.27 g.L-1.h-1). Enzyme titres, however, were favoured by the low DO levels as a maximum of 8.7 U.ml-1, 5.5 fold more than that obtained in batch culture, was achieved, and would be expected to increase proportionally with the biomass. Continuous culture operated at a dilution rate of 0.2 h-1, under strictly aerobic conditions, revealed these conditions to be inhibitory to the lactose consumption rate, however, the non-limiting lactose and high DO environment was favourable for β-galactosidase synthesis, achieving an average of 8 ± 0.9 U.ml-1 in steady state.

The express purpose for doing this project was to develop methods for the continuous culture of E. coli and P. aeruginosa as a mixed population, and to apply these methods in studying the effects of pH and substrate upon the growth of these two organisms in mixed continuous culture.

Fitness, the competitive advantage of an organism or gene, is the basis for adaptation and the emergence of complexity in biology. Competitive advantage is contextual, as it is affected by environmental pressures and ecological interactions. To enable experiments with complex environmental dynamics, we developed eVOLVER, a novel platform for scalable programmable continuous culture. In this thesis, we apply eVOLVER to interrogate how competitive outcomes between strains change according to environmental conditions. Using soil microbe communities as a model ecological system, we tuned dilution rate and frequency across 112 cultures in eVOLVER and observed replicable changes in composition and diversity. Our experimental results challenge intuition about the relationship between diversity and disturbance. In collaborative work, we compared different models of competitive growth in simulations. A Monod growth model outperforms Lotka-Volterra and linear consumer resource models at predicting the effect of varying dilution profiles on microbial diversity. We hypothesize that trade-offs in growth rate and nutritional requirements (r/K) create distinct niches which permit coexistence at certain mortality rates, but collapse under others. These findings suggest a mechanism that potentially affects diversity-disturbance relationships, and confirm that temporal fluctuations can promote diversity. In separate studies, we apply these methods and concepts to 1) study selection on a genome-scale library in yeast under conditions of fluctuating temperature stress in eVOLVER and 2) evaluate the persistence of engineered microbial spores relative to native strains in different “real-world” environments (e.g. soil) and perturbations. Broadly, this dissertation demonstrates that the combination of next-generation sequencing and scalable programmable culture technologies finally enables the types of experiments needed to test decades of theoretical work in ecology and evolution. / 2021-05-18T00:00:00Z