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Biomedical subjects

G St Julian

Publications and source records attributed to G St Julian.

15 recordsLinked to original sources
PubMed1983

Biomass conversion: fermentation chemicals and fuels.

Recent events clearly establish that petroleum can no longer be relied upon as a stable, economical raw material for energy and industrial chemicals. Plant biomass is currently being evaluated as a desirable alternative raw material to petroleum because of renewability and abundance. The most abundant form of biomass on the planet earth is lignocellulose which is composed of cellulose, hemicellulose, and lignin. An estimated 4 X 10(9) tons per year of cellulose alone is readily available for conversion to energy or feedstuffs. This article explores the current state of research on the transformation of cellulose, hemi-cellulose, and lignin by various microorganisms and the subsequent production of fuels and chemicals. Current research activities are covered including technologies available for the utilization of biomass, chemicals from fermentation processes, conversion of biomass to sugar, direct bioconversion to liquid fuels.

Biotransformation↗
PubMed1982

Continuous and static fermentation of glucose to ethanol by immobilized Saccharomyces cerevisiae cells of different ages.

Glucose was converted to ethanol by calcium-alginate-entrapped Saccharomyces cerevisiae NRRL Y-2034 cells that were 24, 48, 72, and 96 h old in continuous-flow and static repeated-batch fermentors. In general, older yeast cells were more efficient than younger ones. In most cases, the continuous fermentations were better than the static ones in producing maximum ethanol yields (5.11 g/10 g of glucose) over extended time periods. The best static fermentation (with 24-h-old cells) converted 100% of the glucose to ethanol for about 12 days, whereas the best continuous fermentation (with 96-h-old cells) converted 100% of the glucose for a remarkable period of about 3 months.

Ethanol↗
PubMed1975

Physiology of sporeforming bacteria associated with insects: metabolism of Bacillus popilliae grown in third-instar Popillia japonica Newman larvae.

The timing and relative participation of concurrent pathways of carbohydrate metabolism as well as the extent of terminal respiratory activity were determined by radiorespirometry with 14-C substrates and by enzyme assays for vegetative and sporulating cells of the bacterium Bacillus popilliae cultured in whole, intact Popillia japonica (Japanese beetle) larvae. During vegetative proliferation, the pentose phosphate pathway predominates in the bacterial cells with minor involvement of the Embden-Meyerhof-Parnas pathway. As the cells proceed through sporulation, pentose phosphate and Embden-Meyerhof-Parnas activity remains constant. No tricarboxylic cycle activity is evident during growth and sporulation of B. popilliae. The results demonstrate (i) predominantly aerobic metabolism for carbohydrate assimilation within in vivo sporulating cells, (ii) a major contrast to the metabolism of other aerobic sporeforming bacteria that exhibit derepression of tricarboxylic acid cycle enzymatic activity at the onset of sporulation, and (iii) no causal necessity of the cycle to B. popilliae sporogeny.

Acetates↗
PubMed1974

Physiology of sporeforming bacteria associated with insects: radiorespirometric survey of carbohydrate metabolism in the 12 serotypes of Bacillus thuringiensis.

Radiorespirometry was used to compare the primary pathways of glucose catabolism in 18 strains of Bacillus thuringiensis representing the 12 established serotypes. Every strain utilizes the Embden-Meyerhof-Parnas pathway almost exclusively; pentose-phosphate pathway participation is minor. The Embden-Meyerhof-Parnas pathway predominates regardless of whether the cells were grown in a minimal medium or one containing yeast extract. The results indicate that the absolute requirement for citrate and related compounds is not a result of defective citrate or glucose transport and metabolism.

Aerobiosis↗
PubMed1974

Physiological and morphological correlation of Rhizopus stolonifer spore germination.

Sporangiospores of Rhizopus stolonifer were examined at various stages of germination by scanning electron and phase-contrast microscopy. These observations were correlated with changes in spore dry weight, spore volume, respiration, and syntheses of ribonucleic acid, deoxyribonucleic acid, and protein during germination.

Carbon Radioisotopes↗
PubMed1973

Scanning electron microscopy of bacterial colonies.

A technique is described for observing bacterial colony growth. Bacillus cereus, B. subtilis, and B. cereus var. mycoides were grown on strips of dialysis membrane layered on nutrient agar. Microcolonies of the organisms on strips were fixed in Formalin vapor in situ; the strips then were removed from the agar and secured to scanning microscope specimen stubs without markedly disturbing the cellular arrangement. Scanning electron micrographs clearly depict morphology of individual cells, as well as the spatial orientation of cells within the colony. This technique is reproducible, adaptable, and simple.

Agar↗
PubMed1972

Germination and outgrowth of single spores of Saccharomyces cerevisiae viewed by scanning electron and phase-contrast microscopy.

Single spores of Saccharomyces cerevisiae were examined during germination and outgrowth by scanning electron and phase-contrast microscopy. Also determined were changes in cell weight and light absorbance, trehalose utilization, and synthesis of protein and KOH-soluble carbohydrates. These studies reveal that development of the vegetative cell from a spore follows a definite sequence of events involving dramatic physical and chemical modifications. These changes are: initial rapid loss in cellular absorbance followed later by an abrupt gain in absorbance; reduction in cell weight and a subsequent progressive increase; modification of the spore surface with concomitant diminution in refractility; elongation of the cell and augmentation of surface irregularities; rapid decline in trehalose content of the cell accompanied by extensive formation of KOH-soluble carbohydrates; and bud formation.

Carbohydrates↗
PubMed1970

Characteristics of a new strain of Bacillus popilliae sporogenic in vitro.

Conditions are described that led to the isolation of NRRL B-2309M, a strain of Bacillus popilliae which sporulates regularly in laboratory culture. Colonies grown on a medium formulated with yeast extract and the ingredients of Mueller-Hinton with phosphate, trehalose, and agar, produced 20% spores in 10 to 12 days. The quantity and kind of yeast extract determine the extent of sporulation, although there are other requirements for optimal growth and sporulation. Spore inocula free of viable vegetative cells are necessary to maintain sporogenicity since asporogenic substrains arise spontaneously on solid and in liquid media. One such substrain, NRRL B-2309N, is also asporogenic in larvae, but lethal, owing to vigorous vegetative growth. Strain B-2309M is infective when vegetative cells or spores are injected into Japanese beetle larvae but fewer spores are formed in vivo than when infections are caused by NRRL B-2309. The characteristics of four related strains of B. popilliae are tabulated.

Agar↗
PubMed1969

Scanning electron and phase-contrast microscopy of bacterial spores.

The three-dimensional immages of free and intrasporangial spores produced by scanning electron microscopy show surface structures not visible by phase-contrast microscopy. Although fine surface detail is not elucidated by scanning electron microscopy, this technique does afford a definitive picture of the general shape of spores. Spores of Bacillus popilliae, B. lentimorbus, B. thuringiensis, B. alvei, B. cereus, and Sarcina ureae have varying patterns of surface ridge formation, whereas spores of B. larvae, B. subtilis, and B. licheniformis have relatively smooth surfaces.

Bacillus↗