Chemistry: molecular biology and microbiology – Micro-organism – per se ; compositions thereof; proces of... – Bacteria or actinomycetales; media therefor
Patent
1988-07-25
1989-10-17
Rosenberg, Peter D.
Chemistry: molecular biology and microbiology
Micro-organism, per se ; compositions thereof; proces of...
Bacteria or actinomycetales; media therefor
4352521, 435300, 435313, C12N 120
Patent
active
048747076
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for producing an aqueous suspension of nitrifying bacteria using a growth medium containing ammonia or nitrite, in which the bacteria remain metabolically and physiologically active by induction of the specific nitrification enzyme systems, in which the bacteria can be kept for long periods and can be finally used, as well as a device for carrying out the process.
Like all viable organisms, bacteria are dependent on permanent energy supply at physiological temperatures. They derive the energy from the metabolization of different substances, whereby various metabolic groups have been created in evolution, specified according to the energy source, the hydrogen donor, and the carbon source. According to the hydrogen donor the organisms are designated as "organotroph" or "lithotroph". In the first case, organic compounds are used as energy source. On the other hand, lithotrophic growth is achieved when inorganic energy sources like H.sub.2, NH.sub.3, H.sub.2 S, S, CO, Fe.sup.2+, NH.sub.4.sup.+ or NO.sub.2.sup.- are used.
Between both metabolic types great differences exist, related to the generation time, when growth of organotrophically growing organisms like Pseudonomas or Escherichia is compared with growth of lithotrophic organisms like Nitrosomonas or Nitrobacter. Escherichia has generation times of approximately 20 min., whereas Nitrobacter has generation times of at least 10 h under lithotrophic conditions. The reason for that difference is the different amount of energy derived from the oxidation of substrates being utilized.
Due to the inorganic substrates used for energy generation, the metabolism of species of nitrifying bacteria is different. The oxidation of ammonia is performed in three steps, first the oxidation of ammonia to hydroxylamine by a monooxygenase. nitrite as the energy generating step. The key enzyme of this reaction is hydroxylamine oxidoreductase. originate from air, but from water. This is shown by the following partial reactions as well as the electrons released from nitrite and transfered to oxygen. +2 H.sup.+ +2 Cyt a.sub.1.sup.2+ a.sub.1.sup.3+ Cyt c.sup.3+ aa.sub.3.sup.3+ +H.sub.2 O transfer to the respiratory chain. Another growth factor is the hydrogen ion concentration. Bacterial growth is dependent on the pH-value and has its optimum at pH 7,8. Higher as well as lower pH-values inhibit bit growth, and they are even toxic with greater deviations from the pH-optimum. Variations of pH-value may occur, when acid is produced by ammonia oxidation, or when organic acids supplied to the medium are metabolized and completely oxidized, resulting in an increase of the pH-value.
Oxygen supply is significant for bacterial growth. Aerobic organisms use molecular oxygen as terminal hydrogen acceptor, whereas anaerobically growing organisms use nitrate or sulfate for example as terminal hydrogen acceptor For the latter, oxygen is toxic even in low concentrations. However, high oxygen partial pressure may be toxic also for aerobic organisms. Furthermore, oxygen requirement changes with the growth phase. If the cells are in the logarithmic growth phase, their oxygen requirement is much higher than in the stationary phase. Resting cells need less oxygen than growing cells. Fast growing organisms like Escherichia coli and Pseudonomas can be grown at high cell concentrations without any problem by the method of a balanced aeration, when process controlled bioreaktors are used.
But so far, no methods exist to achieve such high cell concentrations with active cells of nitrifying bacteria.
Oxygen supply is also a problem when nitrifying bacteria are stored. To have high amounts of those cells available for industrial use, the cells must remain active and be protected against oxygen as well.
These complex relations between the necessary oxygen supply on the one hand and the anaerobic conditions on the other hand require a system for growing cells of different physiological states together.
The object of the invention is to provide a process for growing and stori
REFERENCES:
patent: 755519 (1904-03-01), Moore
patent: 865965 (1907-09-01), Earp-Thomas
patent: 4072577 (1978-02-01), Hurshaut
Anderson Elizabeth M.
Rosenberg Peter D.
TetraWerke Dr.rer.nat. U. Baensch GmbH
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