Derek H. Bone

Relationship between phosphates and alkaline phosphatase of Anabaena flos-aquae in continuous culture

SummaryAnabaena flos-aquae was grown in chemostats with phosphate-limiting growth and dilution rate of 0.015–0.03 h-1. The yields of cells were dependent on dilution rate and a two-fold increase obtained by growth in the presence of 15 mM KNO3. Alkaline phosphatase activity varied 20-fold, lowest activity with excess phosphate light-limited cells and the highest activity with cells grown in the presence of 15 mM KNO3. There was no correlation between hot water soluble phosphate of cells and alkaline phosphatase activity.

Engineering aspects of insect cell suspension culture: a review

SummaryThe development of insect cell suspension culture techniques for the production of insect pathogenic viruses and recombinant proteins has been reviewed, with an emphasis on process scale-up and reactor design considerations. The problems of culture media cost and insect cell shear sensitivity have also been addressed.

Solid state fermentation and fractionation of oat straw by Basidiomycetes

SummarySeventee white-rot and brown-rot fungi were screened for their ability to fractionate the lignocellulose structure of oat straw through the preferential attack of lignin or cellulose. Fermentations were carried out under solid-state conditions with 25 g quantities of straw. The fermented straw was analyzed for weight loss, Klason lignin loss and cellulase digestion. All the fungi attacked both lignin and carbohydrate fractions causing 3–28% weight losses and 26–34 g/100 g enzymatic digestibility. Polyporustulipiferae, Phanerochaetechrysosporium and Polyporus sp. were tested for the effects of various nitrogen, phosphate and carbon levels, incubation temperatures and incubation time. The three fungi had different responses to these factors.

Adaptation of insect cells to suspension culture

Abstract An assessment was made of the effects of successive passages, the concentration of fetal calf serum, and the presence of methyl cellulose and pluronic F-68 on the adaptation of Spodoptera frugiperda and Trichoplusia ni cells from stationary to suspension growth in shake flasks and an external loop airlift bioreactor. The studies showed that it takes about six successive passages to adapt Spodoptera frugiperda cells to suspension growth in shake flasks. The population doubling time was about 35 h with a maximum cell density of 5 × 106 cells/ml. In comparison, pour cell growth was observed for Trichoplusia ni cells in shake flasks. The presence of a higher serum concentration, methyl cellulose, and pluronic, while beneficial for cell growth, was not as important as the passage number. Preliminary experiments with an external loop airlift bioreactor suggest that Spodoptera frugiperda insect cells, previously adapted to shake-flasks, cannot survive air-sparging if the bubble diameter is less than 500 μm.

Kinetics of synthesis of nitrogenase in batch and continuous culture of Anabaena flos-aquae.

SummaryNitrogenase of Anabaena flos-aquae was inactivated by oxygen and recovery of activity was measured in batch and iron, phosphate and urea-limited continuous cultures. In batch culture, canavanine, chloramphenicol, methylamine, proflavine, puromycin and urea inhibited the recovery process. The rate of recovery of nitrogenase activity in continuous cultures was dependent on light intensity, concentration of urea, ammonium salts and nitrate, and independent of growth rate. Oxygen and urea caused an inactivation of nitrogenase in continuous cultures.

Nitrogenase activity and nitrogen assimilation in Anabaena flos-aquae growing in continuous culture

SummaryAnabaena flos-aquae is grown in chemostats under phosphate and urea-limited conditions. Nitrogenase activity in phosphate-limited cells has a maximum activity at a dilution rate of 0.025 h-1 and is repressed 24-fold by 15 mM KNO3. Cultures growing on 1.5 mM nitrate obtain 1/2–2/3 of cell nitrogen from N2. Cells form inducible nitrite assimilating enzymes when grown on nitrate. Algae growing under A or He on limiting urea or phosphate-limited with nitrate have active nitrogenase. The ratio of nitrogenase activity to heterocyst numbers varied 90-fold depending on source of nitrogen, 15 mM KNO3 gave the smallest ratio. The regulatory mechanisms controlling the activity of nitrogenase in blue-green algae is discussed.

Nitrate reduction by denitrifying bacteria in single and two stage continuous flow reactors

Abstract Denitrification by a mixed bacterial population of medium containing 1000 mg NO 3 − -N1 −1 and acetate as carbon source was studied in batch, a single stage continuous flow stirred reactor (CFSTR) and a two stage CFSTR at 30°C. The optimum pH for denitrification, nitratase, nitrite reductase activities and growth was found to be 7.5 in batch culture. A single stage CFSTR growth limited by nitrate had an optimum denitrification rate of 0.13 mg NO 3 − -N mg −1 cells h at a residence time of 8 h. The experimentally observed carbon to nitrate ratio (mg CH 3 COO − -C mg −1 NO 3 − -N)was 1.7 for the dilution rates of 0.02–0.18 h −1 . For the second stage CFSTR, bacteria growing at the maximum rate of 0.25 h −1 and not limited by nitrate had a denitrification rate of 0.24 mg NO 3 − -N mg −1 h. Dissolved oxygen (up to 9.5 mg 1 −1 ) did not effect denitrification rates in the second stage CFSTR. As the second stage CFSTR runs progressed extensive wall growth occurred and concurrently the output gas contained increasing quantities of nitrous oxide. A development from this study would be a two stage CFSTR with wall growth in the second stage which would make an efficient nitrate removal process.

Solid-state fermentation of maple wood by Polyporus anceps

SummarySolid-state fermentations of alkali-treated maple wood shavings were carried out at 30°C in three types of static tray fermenters using Polyporus anceps. Comparison of the fermentation products after 40 days showed a recirculating tower bioreactor (RTB) to be more effective for the production of protein and the consumption of substrate than either a shallow or deep static tray fermentation vessel. Use of the RTB resulted in 70% substrate utilization and a residue containing 17% crude protein.

Production of lipase of Aspergillus foetidus in a batch stirred reactor

SummaryMaximum lipase production byAspergillus foetidus was obtained from cultures grown in the medium of 2% olive oil and 0.5% sucrose. The optimal conditions for the production of lipases in the Multigen fermenters were found to be at 500rpm with an airflow of 1.5 liter per mimute. Immobilization of the fungal source was found to be infeasible in natural polymers.

Submerged cultivation of edible white-rot fungi on tree bark

SummaryThree white-rot fungi,Phanerochaete chrysosporium, Polyporus anceps, andPleurotus sapidus, were grown in shake flasks on maple and cedar bark. The barks for growth were extracted with 1% NaOH and microbial growth was estimated by biuret protein. The maximum yields were 136 and 116 mg protein/gm of bark forPhanerochaete chrysosporium andPolyporus anceps and occurred at 4 days. These two fungi were active cellulase producers and were shown to exhibit an extensive linear phase during batch growth.Pleurotus sapidus produced laccase but negligible growth. A non-linear relationship between bark concentration and protein yield was found.