Microbiology Procedure

Index >> Air Microbiology >> Controlling in Industry

Control in Industry

	Controlling in Industry - The significance of air flora is well understood in industries in which sterile products are prepared, processed, packaged or stored aseptically. These include food industries, pharmaceutical industries and other fermentation industries. In food industries, contamination of the food products by microorganisms may lead to spoilage of the products and may cause food borne illness in consumers who take the spoiled foods. This can be prevented by providing aseptic atmosphere for the processing and packaging of food products.
In pharmaceutical and allied industries where aseptic filling is done or aseptic assembly of sterile products is done, sterile atmosphere is required which can be met by providing filtered sterile air. In fermentation industries, where microorganisms are used for the production of antibiotics, enzymes or organic acids, the significance of air microflora has been well recognized.
These industries employ pure cultures of microorganisms and they have to prevent any further contamination during the fermentation. In aerobic fermentations, where additional aeration is not required, air in the head space is enough to carry out the process. Sterilization of the air in the head space is done along with the sterilization of fermentor. In aerobic fermentations, where additional supply of air is required, air is presterilized and introduced into the sterile fermentor. Thus, even with the addition of large volume of air contamination is prevented by air sterilization. In certain cases, where the pH of the fermentation medium is very low, sterilization of air is not required as the contaminants can not grow at this pH. In industrial fermentation, aerobic processes require the continuous addition of considerable quantities of sterile air.
Although sterilization by heating is technically possible, it has been regarded as a costly process for full-scale operation. The most common method of air sterilization is filtration. Filters for the removal of microorganisms from an environment can be divided into two large groups, absolute filters and fibrous filters. Absolute filters are those in which the pores are smaller than the microorganisms to be removed. Thus, absolute filters are 100% efficient in removing microorganisms.
	Fibrous filters are made up of fibrous materials such as cotton, glass, slag or steel wool and the pores are larger than the particles which are to be removed. For example, the gaps between the fibers are in the range of 0.5 to l5µm. Hence there is always a possibility for the microorganisms to pass through the filter irrespective of the filter depth. Thus the removal of microorganisms by fibrous filter can not be absolute. Despite the efficiency of absolute filters over that of fibrous filters, most fermentation industries are using fibrous filters because they are cheaper and have a lower pressure drop. The simplest air filters consist of a steel casing with an air inlet at the bottom and an outlet at the top. The fibrous material is held in position by grids or perforated plates on either sides.

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