Science Lab Tech Part 3 24-2025 6-7th Lectures PDF

Science Laboratory Technology (SLT) Part (3) Bioreactor A bioreactor refers to any manufactured device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical...

Science Laboratory Technology (SLT) Part (3) Bioreactor A bioreactor refers to any manufactured device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical process is carried out which involves organisms or biochemically active substances derived from such organisms. This process can either be aerobic or anaerobic. These bioreactors are commonly cylindrical, ranging in size from litres to cubic metres, and are often made of stainless steel. It may also refer to a device or system designed to grow cells or tissues in the context of cell culture. These devices are being developed for use in tissue engineering or biochemical/bioprocess engineering. General structure of a continuous stirred-tank type bioreactor On the basis of mode of operation, a bioreactor may be classified as batch, fed batch or continuous (e.g. a continuous stirred-tank reactor model). An example of a continuous bioreactor is the chemostat. Bioreactors are highly nonlinear and many novel control strategies have been proposed for their control. Organisms or biochemically active substances growing in bioreactors may be submerged in liquid medium or may be anchored to the surface of a solid medium. Submerged cultures may be suspended or immobilized. Suspension bioreactors may support a wider variety of organisms, since special attachment surfaces are not needed, and can operate at a much larger scale than immobilized cultures. However, in a continuously operated process the organisms will be removed from the reactor with the effluent. Immobilization is a general term describing a wide variety of methods for cell or particle attachment or entrapment. It can be applied to basically all types of biocatalysis including enzymes, cellular organelles, animal and plant cells and organs. Immobilization is useful for continuously operated processes, since the organisms will not be removed with the reactor effluent, but is limited in scale because the microbes are only present on the surfaces of the vessel. Design A closed bioreactor used in cellulosic ethanol research Bioreactor design is a relatively complex engineering task, which is studied in the discipline of biochemical/bioprocess engineering. Under optimum conditions, the microorganisms or cells are able to perform their desired function with limited production of impurities. The environmental conditions inside the bioreactor, such as temperature, nutrient concentrations, pH, and dissolved gases (especially oxygen for aerobic fermentations) affect the growth and productivity of the organisms. The temperature of the fermentation medium is maintained by a cooling jacket, coils, or both. Particularly exothermic fermentations may require the use of external heat exchangers. Nutrients may be continuously added to the fermenter, as in a fed-batch system, or may be charged into the reactor at the beginning of fermentation. The pH of the medium is measured and adjusted with small amounts of acid or base, depending upon the fermentation. For aerobic (and some anaerobic) fermentations, reactant gases (especially oxygen) must be added to the fermentation. Since oxygen is relatively insoluble in water (the basis of nearly all fermentation media), air (or purified oxygen) must be added continuously. The action of the rising bubbles helps mix the fermentation medium and also "strips" out waste gases, such as carbon dioxide. In practice, bioreactors are often pressurized; this increases the solubility of oxygen in water. In an aerobic process, optimal oxygen transfer is sometimes the rate limiting step. Oxygen is poorly soluble in water—even less in warm fermentation broths—and is relatively scarce in air (20.95%). Oxygen transfer is usually helped by agitation, which is also needed to mix nutrients and to keep the fermentation homogeneous. Gas dispersing agitators are used to break up air bubbles and circulate them throughout the vessel. Fouling can harm the overall efficiency of the bioreactor, especially the heat exchangers. To avoid it, the bioreactor must be easily cleaned. Interior surfaces are typically made of stainless steel for easy cleaning and sanitation. Typically bioreactors are cleaned between batches, or are designed to reduce fouling as much as possible when operated continuously. Heat transfer is an important part of bioreactor design; small vessels can be cooled with a cooling jacket, but larger vessels may require coils or an external heat exchanger. Types Photobioreactor Moss photobioreactor with Physcomitrella patens A photobioreactor (PBR) is a bioreactor which incorporates some type of light source (that may be natural sunlight or artificial illumination). Virtually any translucent container could be called a PBR. Photobioreactors are used to grow small phototrophic organisms such as cyanobacteria, algae, or moss plants. These organisms use light through photosynthesis as their energy source. Consequently, risk of contamination with other organisms like bacteria or fungi is lower in photobioreactors when compared to bioreactors for heterotroph organisms. Sewage treatment Conventional sewage treatment utilises bioreactors to undertake the main purification processes. In some of these systems, a chemically inert medium with very high surface area is provided as a substrate for the growth of biological film. Separation of excess biological film takes place in settling tanks or cyclones. In other systems aerators supply oxygen to the sewage and biota to create activated sludge in which the biological component is freely mixed in the liquor in "flocs". In these processes, the liquid's biochemical oxygen demand (BOD) is reduced sufficiently to render the contaminated water fit for reuse. The biosolids can be collected for further processing, or dried and used as fertilizer. An extremely simple version of a sewage bioreactor is a septic tank whereby the sewage is left in situ, with or without additional media to house bacteria. In this instance, the biosludge itself is the primary host for the bacteria. Many research groups have developed novel bioreactors for growing specialized tissues and cells on a structural scaffold, in attempt to recreate organ-like tissue structures in-vitro. Among these include tissue bioreactors that can grow heart tissue, skeletal muscle tissue, ligaments, cancer tissue models, and others. Currently, scaling production of these specialized bioreactors for industrial use remains challenging and is an active area of research. Biosafety cabinet Biosafety cabinet A microbiologist performing influenza research within a biosafety cabinet Acronym BSC Other Biological safety cabinet, microbiological names safety cabinet Uses Biocontainment Related Laminar flow cabinet items Fume hood Glove box A biosafety cabinet (BSC), also called a biological safety cabinet or microbiological safety cabinet—is an enclosed, ventilated laboratory workspace for safely working with materials contaminated with (or potentially contaminated with) pathogens requiring a defined biosafety level. Several different types of BSC exist, differentiated by the degree of biocontainment they provide. BSCs first became commercially available in 1950. Purposes The primary purpose of a BSC is to serve as a means to protect the laboratory worker and the surrounding environment from pathogens. All exhaust air is HEPA-filtered as it exits the biosafety cabinet, removing harmful bacteria and viruses. This is in contrast to a laminar flow clean bench, which blows unfiltered exhaust air towards the user and is not safe for work with pathogenic agents. Neither are most BSCs safe for use as fume hoods. Likewise, a fume hood fails to provide the environmental protection that HEPA filtration in a BSC would provide. However, most classes of BSCs have a secondary purpose to maintain the sterility of materials inside (the "product"). DNA sequencer A DNA sequencer is a scientific instrument used to automate the DNA sequencing process. Given a sample of DNA, a DNA sequencer is used to determine the order of the four bases: G (guanine), C (cytosine), A (adenine) and T (thymine). This is then reported as a text string, called a read. Some DNA sequencers can be also considered optical instruments as they analyze light signals originating DNA sequencer from fluorochromes attached to nucleotides. The Sanger sequencing method in 2001 formed the basis of the "first generation" of DNA sequencers which enabled the completion of the human genome project in 2001. This first generation of DNA sequencers are essentially automated electrophoresis systems that detect the migration of labelled DNA fragments. Therefore, these sequencers can also be used in the genotyping of genetic markers where only the length of a DNA fragment(s) needs to be determined. Because of limitations in DNA sequencer technology, the reads of many of these technologies are short, compared to the length of a genome therefore the reads must be assembled into longer contigs. DNA sequencer manufacturers use a number of different methods to detect which DNA bases are present. The specific protocols applied in different sequencing platforms have an impact in the final data that is generated. Therefore, comparing data quality and cost across different technologies can be a daunting task. Since these systems rely on different DNA sequencing approaches, choosing the best DNA sequencer and method will typically depend on the experiment objectives and available budget. Fume hood Fume hood A common modern fume hood. Other names Hood Fume cupboard Fume closet Uses Fume removal; Blast or flame shield Related items Laminar flow cabinet A fume hood (sometimes called a fume cupboard or fume closet) is a type of local ventilation device that is designed to limit exposure to hazardous or toxic fumes, vapors or dusts. Description A fume hood is typically a large piece of equipment enclosing five sides of a work area, the bottom of which is most commonly located at a standing work height. Two main types exist, ducted and recirculating (ductless). The principle is the same for both types: air is drawn in from the front (open) side of the cabinet, and either expelled outside the building or made safe through filtration and fed back into the room. This is used to:  protect the user from inhaling toxic gases (fume hoods, biosafety cabinets, glove boxes)  protect the product or experiment (biosafety cabinets, glove boxes)  protect the environment (recirculating fume hoods, certain biosafety cabinets, and any other type when fitted with appropriate filters in the exhaust airstream) Secondary functions of these devices may include explosion protection, spill containment, and other functions necessary to the work being done within the device. Fume hoods are generally set back against the walls and are often fitted with infills above, to cover up the exhaust ductwork. Because of their recessed shape they are generally poorly illuminated by general room lighting, so many have internal lights with vapor-proof covers. The front is a sash window, usually in glass, able to move up and down on a counterbalance mechanism. Standard Glove box with Inert gas purification system For exceptionally hazardous materials, an enclosed glovebox may be used, which completely isolates the operator from all direct physical contact with the work material and tools. The enclosure may also be maintained at negative air pressure to ensure that nothing can escape via minute air leaks. Control panels Most fume hoods are fitted with a mains-powered control panel. Typically, they perform one or more of the following functions:  Warn of low air flow  Warn of too large an opening at the front of the unit (a "high sash" alarm is caused by the sliding glass at the front of the unit being raised higher than is considered safe, due to the resulting air velocity drop)  Allow switching the exhaust fan on or off  Allow turning an internal light on or off Ducted fume hoods Labs Ducted Fume Hood Most fume hoods for industrial purposes are ducted. A large variety of ducted fume hoods exist. In most designs, conditioned (i.e. heated or cooled) air is drawn from the lab space into the fume hood and then dispersed via ducts into the outside atmosphere. The fume hood is only one part of the lab ventilation system. Because recirculation of lab air to the rest of the facility is not permitted, air handling units serving the non-laboratory areas are kept segregated from the laboratory units. To improve indoor air quality, some laboratories also utilize single-pass air handling systems, wherein air that is heated or cooled is used only once prior to discharge. Many laboratories continue to use return air systems to the laboratory areas to minimize energy and running costs, while still providing adequate ventilation rates for acceptable working conditions. The fume hoods serve to evacuate hazardous levels of contaminant. To reduce lab ventilation energy costs, variable air volume (VAV) systems are employed, which reduce the volume of the air exhausted as the fume hood sash is closed. This product is often enhanced by an automatic sash closing device, which will close the fume hood sash when the user leaves the fume hood face. The result is that the hoods are operating at the minimum exhaust volume whenever no one is actually working in front of them. Since the typical fume hood in US climates uses 3.5 times as much energy as a home, the reduction or minimization of exhaust volume is strategic in reducing facility energy costs as well as minimizing the impact on the facility infrastructure and the environment. Particular attention must be paid to the exhaust discharge location, to reduce risks to public safety, and to avoid drawing exhaust air back into the building air supply system. Cleanroom Entrance to a cleanroom with no air shower A cleanroom or clean room is an engineered space, which maintains a very low concentration of airborne particulates. It is well isolated, well-controlled from contamination, and actively cleansed. Such rooms are commonly needed for scientific research, and in industrial production for all nanoscale processes, such as semiconductor manufacturing. A cleanroom is designed to keep everything from dust, to airborne organisms, or vaporised particles, away from it, and so from whatever material is being handled inside it. The other way around, a cleanroom can also help keep materials escaping from it. This is often the primary aim in hazardous biology and nuclear work, in pharmaceutics and in virology. Overview A clean room is a necessity in semiconductor manufacturing, rechargeable battery industry, the life sciences, and any other field that is highly sensitive to environmental contamination. Cleanrooms can range from the very small to the very large. On the one hand, a single user laboratory can be built to cleanroom standards within several square meters, and on the other entire manufacturing facilities can be contained within a cleanroom with factory floors covering thousands of square meters. Between the large and the small, there are also modular cleanrooms. Basic construction First, outside air entering a cleanroom is filtered and cooled by several outdoor air handlers using progressively finer filters to exclude dust. Within, air is constantly recirculated through fan units containing high-efficiency particulate absorbing filters (HEPA), and/or ultra-low particulate air (ULPA) filters to remove internally generated contaminants. Special lighting fixtures, walls, equipment and other materials are used to minimize the generation of airborne particles. Plastic sheets can be used to restrict air turbulence, if the cleanroom design is of the laminar airflow type. Air temperature and humidity levels inside a cleanroom are tightly controlled, because they affect the efficiency and means of air filtration. If a particular room requires low enough humidity to make static electricity a concern, it too will be controlled by e.g. introducing controlled amounts of charged ions into the air, using a corona discharge. Static discharge is of particular concern in the electronics industry, where it can instantly destroy components and circuitry. Equipment inside any cleanroom is designed to generate minimal air contamination. The selection of material for the construction of a cleanroom should not generate any particulates, hence monolithic epoxy or polyurethane floor coating is preferred. Buffed stainless steel or powder-coated mild steel sandwich partition panels and ceiling panel are used, instead of iron alloys prone to rusting and then flaking. Corners like the wall to wall, wall to floor, wall to ceiling are avoided by providing coved surface and all joints need to be sealed with epoxy sealant to avoid any deposition or generation of particles at the joints, by vibration and friction. Personnel contamination of cleanrooms The greatest threat to cleanroom contamination comes from the users themselves. In the healthcare and pharmaceutical sectors, control of microorganisms is important, especially microorganisms likely to be deposited into the air stream from skin shedding. Studying cleanroom microflora is of importance for microbiologists and quality control personnel to assess changes in trends. Shifts in the types of microflora may indicate deviations from the "norm" such as resistant strains or problems with cleaning practices. In assessing cleanroom micro-organisms, the typical flora are primarily those associated with human skin (Gram-positive cocci), although microorganisms from other sources such as the environment (Gram-positive rods) and water (Gram- negative rods) are also detected, although in lower number. Common bacterial genera include Micrococcus, Staphylococcus, Corynebacterium, and Bacillus, and fungal genera include Aspergillus and Penicillium.