Hydrogen production by biological processes: a survey of literature

The process of surface adhesion and biofilm development is a survival strategy employed by virtually all bacteria and refined over millions of years. This process is designed to anchor microorganisms in a nutritionally advantageous environment and to permit their escape to greener pastures when essential growth factors have been exhausted. Bacterial attachment to a surface can be divided into several distinct phases, including primary and reversible adhesion, secondary and irreversible adhesion, and biofilm formation. Each of these phases is ultimately controlled by the expression of one or more gene products. Ultrastructurally, the mature bacterial biofilm resembles an underwater coral reef containing pyramidal or mushroom-shaped microcolonies of organisms embedded within an extracellular glycocalyx, with channels and cavities to allow the exchange of nutrients and waste. The biofilm protects its inhabitants from predators, dehydration, biocides, and other environmental extremes while regulating population growth and diversity through primitive cell signals. From a physiological standpoint, surface-bound bacteria behave quite differently from their planktonic counterparts. Recognizing that bacteria naturally occur as surface-bound and often polymicrobic communities, the practice of performing antimicrobial susceptibility tests using pure cultures and in a planktonic growth mode should be questioned. That this model does not reflect conditions found in nature might help explain the difficulties encountered in the management and treatment of biomedical implant infections.

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Bacterial Adhesion: Seen Any Good Biofilms Lately?

Microalgae are a promising alternative source of lipid for biodiesel production. One of the most important decisions is the choice of species to use. High lipid productivity is a key desirable characteristic of a species for biodiesel production. This paper reviews information available in the literature on microalgal growth rates, lipid content and lipid productivities for 55 species of microalgae, including 17 Chlorophyta, 11 Bacillariophyta and five Cyanobacteria as well as other taxa. The data available in the literature are far from complete and rigorous comparison across experiments carried out under different conditions is not possible. However, the collated information provides a framework for decision-making and a starting point for further investigation of species selection. Shortcomings in the current dataset are highlighted. The importance of lipid productivity as a selection parameter over lipid content and growth rate individually is demonstrated.

Lipid productivity as a key characteristic for choosing algal species for biodiesel production

http://fac.ksu.edu.sa/sites/default/files/Abdel-Raouf%20et%20al%2C2012.pdf

Microalgae and wastewater treatment.

Photobioreactors for mass cultivation of algae.

Cells of the non-N2-fixing cyanobacteriumPhormidium laminosum were immobilized in polyurethane (PU) foams either by absorption or by entrapment in the PU prepolymer followed by polymerisation and by adsorption onto polyvinyl (PV) foams. Although entrapment caused toxicity problems which lead to rapid death of the immobilized cells, they were immobilized successfully by adsorption onto PU or PV foams and maintained their photosynthetic electron transport activities (PS I, II, I + II) for at least 7 weeks. Changes in the morphology resulting from immobilization, as revealed by scanning electron microscopy (SEM) and low temperature-SEM, were investigated. Batch cultures and a continuous-flow packed bed photobioreactor were used to study nitrate removal from water. The effects of light intensity and CO2 concentration on bioreactor performance were studied with respect to the nitrate uptake efficiency of the system. It was concluded thatP. laminosum immobilized on polymer foams is of potential value for biological nitrate removal in a continuous-flow system.

Removal of nitrate from water by foam-immobilized Phormidium laminosum in batch and continuous-flow bioreactors

Neuropharmacology and Physiology. Peripheral Chemoreceptors: Sensors of Metabolic Status. Central Chemoreceptors. Suprapontine Control of Breathing. Measurement of Drug Effects of Ventilatory Control. Response Surface Modeling of Drug Interactions: Model Selection and Multimodel Inference Using the Bootstrap. Respiratory Neuroplasticity: Respiratory Gases, Development, and Spinal Injury. Airway Reflexes in Humans. Inheritance and Ventilatory Behavior in Animal Models. Pathophysiology. Congenital Central Hypoventilation Syndrome: Should we Rename it Congenital Autonomopathy? Upper Airway Obstruction in Obstructive Sleep Apnea. High Altitude. Obesity and the Control of Breathing. Clinical Pharmacology. Pain Management and Regional Anesthesia. Ventilatory Effects of Medications Used for Moderate and Deep Sedation. Central Effects of General Anesthesia. The Influence of Inhalational Anesthetics on Carotid Body Mediated Ventilatory Responses. General Anesthesia and Respiratory Mechanics. Recovery from Anesthesia. Neuromuscular Blocking Agents and Ventilation. Cardiovascular Drugs and the Control of Breathing

Physiological models in microbiology

Hydrogen photoproduction and carbon dioxide uptake by immobilized Anabaena variabilis in a hollow-fiber photobioreactor

A kinetic model representing the pathway for the biosynthesis of penicillin by P. chrysogenum has been developed. The model is capable of describing the flux through the biosynthetic pathway, and model simulations correspond well with measurements of intermediates and end products. One feature of the present model structure is that it assumes the kinetics of the enzyme isopenicillin N synthetase (IPNS) to be first order with respect to the dissolved oxygen concentration in the range of 0.070 to 0.18 mM (25% to 70% saturation with air). Thus, it indicates the importance that molecular oxygen has on the rate of the reaction catalyzed by this enzyme, and consequently as an enhancer of the specific rate of penicillin production. Using the kinetic model, metabolic control analysis (MCA) of the pathway was performed. The determined flux control coefficients suggested that, during the production phase, the flux is controlled by IPNS as this enzyme becomes saturated with tripeptide δ-(L-α-amino-adipyl)-L-cysteinyl-D-valine (LLD-ACV). In the simulations, oxygen was shown to be a bottleneck alleviator by stimulating the rate of IPNS which prevents the accumulation of LLD-ACV. As a consequence of this stimulation, the rate-controlling step was moved to another place in the pathway. © 1996 John Wiley & Sons, Inc.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/bit.260520502

Pathway kinetics and metabolic control analysis of a high-yielding strain of Penicillium chrysogenum during fed batch cultivations.

This review surveys data on cyanobacterial hydrogen photoproduction with a view to a use of cyanobacteria in photobioreactors for hydrogen production.

Michael J. Bazin

Papers

Removal of nitrate from water by foam-immobilized Phormidium laminosum in batch and continuous-flow bioreactors

Physiological models in microbiology

Hydrogen photoproduction and carbon dioxide uptake by immobilized Anabaena variabilis in a hollow-fiber photobioreactor

Pathway kinetics and metabolic control analysis of a high-yielding strain of Penicillium chrysogenum during fed batch cultivations.

The potential of using cyanobacteria in photobioreactors for hydrogen production