Fermentation aseptic

For CSTF runs, we need to have nutrient and product reservoirs which are connected to the fermenter aseptically. The rate of input and output stream needs to be controlled precisely. Sometimes, the control of the outlet flowrate can be difficult due to the foaming or plugging by large cell aggregates. Since the length of the run should last several days or even weeks to reach a steady state and also to vary the dilution rates, there is always a high risk for the fermenter to be contaminated. Frequently, it is difficult to reach a steady state because of the cell s mutation and adaptation to new environment. 

In monoculture the substrate is pasteurized or sterilized and inoculated with a pure culture. During the fermentation aseptic procedures may be used to prevent contamination. In some cases the conditions may select against contaminants and the process organism may grow vigorously so that any contaminants caimot compete. In these cases the process maybe able to be carried out by unskilled operators. 

In large-scale SSF, it is difficult to continuously monitor the pH change, and hence it is advised to use buffers in the medium. In open systems such as tray fermentation, aseptic operation is not possible and therefore pH and moisture play a crucial role in reducing the risk of contamination. 

An industrial fermentor of capacity up to several hundred kiloliters equipped with aeration and stirring devices, as well as other automatic control systems, is used. The cultures must be sterilized and aseptic air must be used owing to the high sensitivity to bacterial contamination of L-glutamic acid fermentation. 

Transfer of fluid in a fermentation plant usuallv makes use of air pressure differences. One or more manifold headers may interconnect many vessels. As transfers may have to be aseptic, headers are pressurized with steam until needed. A typical arrangement of steam seals is shown in Fig. 24-12. 

Aseptic Free from living germs of disease, fermentation or putrefaction. 

After 55 hours of fermentation, the contents of the round flask is transferred under aseptic conditions into a metal reactor of about 100 liters capacity containing 60 liters of sterile medium prepared as follows ... 

The mixture of broth and mycelium thus formed was then transferred under aseptic conditions to a 3-iiter fermentor containing 2 00 ml of a sterile fermentation medium having the following composition 60 g Cerelose (dextrose hydrate), 18 g soybean meal, 5 g distillers solubles, 12 g cornmeal and tap water in a sufficient amount for a 1,000-ml total volume, adjusted to pH 7.0 to 7.2 with potassium hydroxide. 

Tank fermentation of Micromonospora inyoensis — Germination stage 1 Under aseptic conditions, add a lyophilized culture (or cells obtained from a slant culture) of M. inyoensis to a 300 ml shake flask containing 100 ml of the following sterile medium ... 

A spore sand culture containing Gibberella zeae (Gordon) NRRL-2830 was aseptically placed in a sterile tube containing 15 ml of Czapek s-Dox solution and a small amount of agar. This medium was then incubated for about 168 hours at approximately 25°C. At the end of the incubation period, the medium was washed with 5 ml of steriledeionized water and transferred to a sterile tube containing 45 ml of Czapek s-Dox solution. The contents of the tube were then incubated for about 96 hours at about 25°C after which the material was available for use in inoculation of a fermentation medium. 

To produce Candida sp. as food additive the above process could be operated, except that fermentation would have to be aseptic (with sterilisation costs). The cost would be 0.647 + 0.04 = 0,687 per kg biomass or 1.145 per kg protein. 

To produce Fusarium sp. as feed, the cheapest option would be non-aseptic fermentation, filtration and diying. The cost is thus 0.649 + 0.001 + 0.02 = 0,670 per kg biomass. 

To produce Fusarium sp. as high-protein food additive, the above system could be used, with aseptic fermentation and grinding the product after drying. The cost is thus 0.670 + 0.04 + 0.01 = 0,720 per kg biomass. 

Normally, fermentation processes can be classified depending on the objective of study. For example, in terms of products fermentation is divided into 4 types, namely, microbial cell, microbial enzyme, microbial metabolite and transformation process. If considering due to its contaminating conditions, it will be classified into 3 types septic, semi-septic and aseptic fermentation. However, in general, the fermentation processed are classified into 3 types as follows. 

All laboratory operations are carried out in laminar flow cabinets in rooms in which filtered air is maintained at a slight positive pressure relative to their outer environment. Operators wear sterilized clothing and work aseptically. Antibiotic fermentations are, of strict necessity, pure culture aseptic processes, without con-tamirrating orgarrisms. 

Not all the nutrients required during fermentation are initially provided in the culture medium. Some are sterilized separately by batch or continuous sterilization and then added whilst the fermentation is in progress, usually via automatic systems that allow a preset programme of continuous or discrete aseptic additions. 

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