P. D. Sayer

Bio: P. D. Sayer is an academic researcher from Salisbury University. The author has an hindex of 1, co-authored 1 publications receiving 18 citations.

Production of Escherichia coli as a source of nucleic acids

Abstract: Present-day chemical and physical studies of the nucleic acid system of bacteria frequently call for quantities of cells which are beyond the capacity of traditional culture methods such as that of the shake flask. The case is therefore argued for an increased use of stirred deep cultures because a greater rate of output, at a higher cell concentration and with improved control of cultural conditions can be achieved. For the isolation of deoxyribonucleic acid and transfer ribonucleic acid, low growth-rate cells should be the most prolific source: whereas for ribosomes, ribosomal ribonucleic acid and messenger ribonucleic acid, high growth cells should give bigger yields. It is concluded that the information is somewhat obscure on what are the best growth conditions for the production of the related-enzymes. A batch method for producing low growth-rate cells of Escherichia coli, in lots of 1 kg dry wt., is then described, followed by a continuous method for producing high growth-rate cells, with an output of 3 kg of dry cells per day. Both cultures have been designed to give maximum yield of cells by promoting maximum assimilation of the carbon substrate. From the point of view of designing a culture, the section dealing with the continuous process discusses the rationale of medium formulation, the calculation of aeration requirements and briefly reviews earlier work on the kinetics of continuous culture.

The evidence for the airborne spread of Newcastle disease.

Abstract: Newcastle disease virus has been shown to survive when airborne in small particles, both in the laboratory and in the open air. Field outbreaks have been studied and viable virus has been recovered from the open air short distances downwind of infected premises. Vaccination of birds leads to a great reduction in the amount of virus liberated into the air.

Investigation of the unit operations involved in the continuous flow isolation of β‐galactosidase from Escherichia coli

Abstract: A 1000 liter fermentor has been used to produce a continuous feed of Escherichia coli containing a high level of β-galactosidase. We have investigated the individual unit operations for the isolation of the enzyme: cell disruption, nucleic acid removal, protein precipitation, and solid–liquid separation after each stage. Using the information obtained we have been able to operate a semicontinuous process which when fully continuous would yield 100 g protein/hr, comprising 23% β-galactosidase.

Phosphoglucose isomerase from Escherischia coli K10: Purification, properties and formation under aerobic and anaerobic condition

Abstract: Phosphoglucose isomerase has been purified from crude extracts of Escherichia coli K10. Two forms of the enzyme were separated during the purification procedure. The major species comprises more than 90% of the enzyme activity, has an apparent molecular weight of about 125,000 and consists of two 59,000 molecular weight subunits; the minor species has an apparent size of 230,000 and consists of (possibly four) subunits of 59,000 molecular weight. Both enzyme forms have the same N-terminal amino acid, the same pH optimum of reaction and the same kinetic constants for the substrate fructose-6-phosphate and the inhibitor 6-phosphogluconate. They differ in that the minor species has half the specific enzyme activity compared to the major one and that its subunit polypeptide carries a higher electronegative charge. Since they are both coded by the pgi gene and since they show full immunological identity it seems that the minor species is a dimer of the major enzyme form and that dimerisation is caused by subunit modification. No physiological role could be found for the existence of the two forms. — Formation of phosphoglucose isomerase is under respiratory control: under anaerobiosis the enzyme (both species) is derepressed parallely with other glycolytic enzymes.

The kinetics of cholesterol oxidase synthesis by Nocardia rhodocrous.

Abstract: The production of cholesterol oxidase by 3 liter batch cultures of Nocardia rhodocrous growing on a glycerol/yeast extract medium was investigated. Cholesterol was shown to be a good inducer of the enzyme. The optimum time for cholesterol addition and the quantity to be added were determined, resulting in a 15-fold yield increase. Cholesterol oxidase synthesis was influenced by the dissolved oxygen tension. Maximum cholesterol oxidase production was obtained at 30-40% air saturation. The effect of growth conditions on the extraction of cholesterol oxidase by Triton X-100 was investigated. The scale-up of the fermentation to 800 liters in a pilot-plant fermenter is described.