Nutritional factors bacterial growth

Dextran can be produced either directly by batch fermentation or indirectly by the use of the enzyme complex dextransucrase mentioned above. Direct production is, of course, the simpler process, but molecular weights of dextrans are varying. The fermentation process is performed in stirred and aerated bioreactors with typical volumes of up to 200 m. Bacterial growth requires amino acids and growth factors. Fermentation is started at 25 - 30 C and a pH of 6.5 - 7.0, dropping to about 4.5 at the end of the production cycle (after about 48 hours) due to formation of lactic acid as a by-product. Maintenance of an adequate dissolved oxygen concentration is problematic due to the non-Newtonian fluid behavior of the nutritional... 

These quotations contain in essence a general conception of bacterial nutrition and its wider aspects which the work of succeeding years has developed and enriched. Twort and Ingram attempted to isolate the active substance synthesized by Mijeo. phlei which was required by Johne s bacillus. They thus made one of the earliest studies in the field of bacterial growth factors. Twort and Ingram s book (391) is certainly One of the few classics in the history of bacterial chemistry. 

A complex interplay of host and pathogen factors influences the acquisition and development of fungal infections. Intact skin or mucosal surfaces serve as primary barriers to infection. Desiccation, epithelial cell turnover, fatty acid content, and low pH of the skin are believed to be important factors in host resistance. Bacterial flora of the skin and mucous membranes compete with fungi for growth. Alterations in the balance of normal flora caused by the use of antibiotics or alterations in nutritional status can allow the proliferation of fungi such as Candida, increasing the likelihood of systemic invasion and infection. ... 

The association of duration of catheterization, with the incidence of catheter positive sepsis has been widely debated. Some believe duration to be a factor (14,18,22,31), and others do not (10,44). The latter group believe that the catheter is contaminated at the time of introduction. In our experience (Table 4) duration does appear to be a factor. The ability of the nutritive solutions to support bacterial and fungal growth is now well established (12, 14,43). Candida albicans will grow particularly well in casein hydrolysates with dextrose, and in intravenous soy bean fat emulsions. 

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