These are specialized bioreactors for fermentation which can be carried out either by exposure to sunlight or artificial lighting. Since artificial lighting is expensive, only outdoor photobioreactors are preferred. Some important compounds are produced using Ex photobioreactor, B-carotene astaxanthin. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay Different types of photobioreactors are shown in fig. they are made of glass or more commonly transparent plastic. The series of tubes or flat panels constitute the light receiving systems (solar receivers). The crop can be circulated via pumps or airlift pumps. It is essential that the cells are in continuous circulation without sediment forming and that adequate sunlight penetration is maintained. The tube should also be sealed to prevent temperature rise. Photobioreactors are usually operated in continuous mode at temperatures between 25 and 45 C. Normally microalgae and cyanobacteria are used. Organisms grow during daylight while products are produced during night. Types of Photobioreactors: Photobioreactors are differentiated into two types: Open system Closed system Open system: - The first approach for the controlled production of phototrophic organisms was and still is an open natural pond or artificial track pond. In there, the culture suspension, which contains all the necessary nutrients and carbon dioxide, is pumped around in a cycle, being illuminated directly by sunlight through the surface of the liquid. This construction principle is the simplest way of production for phototrophic organisms. But due to their death (up to 0.3 m) and the associated reduced average light supply, open systems achieve only limited real productivity rates. Furthermore, energy consumption is relatively high, since it is necessary to dispose of a high quantity of water containing a low concentration of product. elaborate. Open space is expensive in densely populated areas, while water is rare in others. The use of open technologies causes high water losses due to evaporation into the atmosphere. Please note: this is just an example. Get a custom paper from our expert writers now. Get a Custom Essay Closed System: - Since the 1950s several approaches have been conducted to develop closed systems, which theoretically provide higher cell densities of phototrophic organisms and therefore a lower demand for water to be pumped than open systems. Furthermore, the closed concentration avoids system-related water losses and the risk of contamination due to landing waterfowl or dust is minimised. All modern photobioreactors have attempted to find a balance between a thin layer of culture suspension, optimized light application, low pumping energy consumption, capital expenditure and microbial purity. Many different systems have been tested, but only a few approaches have been able to work on an industrial scale. Examples of closed system photobioreactor which are redesigned laboratory fermenters, tubular photobioreactor, Christmas tree photobioreactor and horizontal photobioreactor.