Modern Industrial Microbiology and Biotechnology

10 Modern Industrial Microbiology and BiotechnologyThe first meaning relates to microbial physiology. In strict physiological terms,fermentation is defined in microbiology as the type of metabolism of a carbon source inwhich energy is generated by substrate level phosphorylation and in which organicmolecules function as the final electron acceptor (or as acceptors of the reducingequivalents) generated during the break-down of carbon-containing compounds orcatabolism. As is well-known, when the final acceptor is an inorganic compound theprocess is called respiration. Respiration is referred to as aerobic if the final acceptor isoxygen and anaerobic when it is some other inorganic compound outside oxygen e.gsulphate or nitrate.The second usage of the word is in industrial microbiology, where the term‘fermentation’ is any process in which micro-organisms are grown on a large scale, evenif the final electron acceptor is not an organic compound (i.e. even if the growth is carriedout under aerobic conditions). Thus, the production of penicillin, and the growth of yeastcells which are both highly aerobic, and the production of ethanol or alcoholic beverageswhich are fermentations in the physiological sense, are all referred to as fermentations.The third usage concerns food. A fermented food is one, the processing of which microorganismsplay a major part. Microorganisms determine the nature of the food throughproducing the flavor components as well deciding the general character of the food, butmicroorganisms form only a small portion of the finished product by weight. Foods suchas cheese, bread, and yoghurt are fermented foods.1.5 ORGANIZATIONAL SET-UP IN AN INDUSTRIALMICROBIOLOGY ESTABLISHMENTThe organization of a fermentation industrial establishment will vary from one firm toanother and will depend on what is being produced. Nevertheless the diagram in Fig. 1.1represents in general terms the set-up in a fermentation industry.The culture usually comes from the firm’s culture collection but may have been sourcedoriginally from a public culture collection and linked to a patent. On the other hand itmay have been isolated ab initio by the firm from soil, the air, the sea, or some other naturalbody. The nutrients which go into the medium are compounded from various rawmaterials, sometimes after appropriate preparation or modification includingsaccharification as in the case of complex carbohydrates such as starch or cellulose. Aninoculum is first prepared usually from a lyophilized vial whose purity must be checkedon an agar plate. The organism is then grown in shake flasks of increasing volumes untilabout 10% of the volume of the pilot fermentor is attained. It is then introduced into pilotfermentor(s) before final transfer into the production fermentor(s) (Fig. 1.2).The extraction of the material depends on what the end product is. The methods areobviously different depending on whether the organism itself, or its metabolic product isthe desired commodity. If the product is the required material the procedure will bedictated by its chemical nature. Quality control must be carried out regularly to ensurethat the right material is being produced. Sterility is important in industrial microbiologyprocesses and is maintained by various means, including the use of steam, filtration or bychemicals. Air, water, and steam and other services must be supplied and appropriatelytreated before use. The wastes generated in the industrial processes must also be disposed