Notes

v. The organism should have a reasonable genetic and physiological stability. An organism which mutates easily is an expensive risk. It could produce undesired products if a mutation occurred unobserved. The result could be reduced yield of the expected material, production of an entirely different product, or even a toxic material. None of these situations is a help towards achieving the goal of the industry, which is the maximization of profits through the production of goods with predictable properties to which the consumer is accustomed to. vi. The organism should lend itself to a suitable method of product harvest at the end of the fermentation. If, for example, a yeast and a bacterium were equally suitable for manufacturing a certain product, it would be better to use the yeast if the most appropriate recovery method was centrifugation. This is due to the bacterial diameter of approximately 1 μm, while yeasts are approximately 5 μm. Assuming their densities are the same, yeasts would sediment 25 times more rapidly than bacteria. The faster sedimentation would result in less expenditure in terms of power, personnel supervision, etc. which could translate to higher profit. vii. Wherever possible, organisms which have physiological requirements which protect them against competition from contaminants should be used. An organism with optimum productivity at high temperatures, low pH values or which is able to elaborate agents inhibitory to competitors has a decided advantage over others. Thus, a thermophilic efficient producer would be preferred to a mesophilic one. viii. The organism should be reasonably resistant to predators such as Bdellovibrio spp. or bacteriophages. It should therefore be part of the fundamental research of an industrial establishment using a phage-susceptible organism to attempt to produce phage-resistant, yet high yielding, strains of the organism.ix. Where practicable, the organism should not demand large amounts of oxygen as aeration (through greater power demand for agitation of the fermenter impellers, forced air injection, etc.) contributes about 20% of the cost of the finished product.x. Lastly, the organism should be fairly easily amenable to genetic manipulation to enable the establishment of strains with more acceptable properties.