Chemistry: molecular biology and microbiology – Micro-organism – per se ; compositions thereof; proces of... – Bacteria or actinomycetales; media therefor
Patent
1994-09-22
1996-11-12
Naff, David M.
Chemistry: molecular biology and microbiology
Micro-organism, per se ; compositions thereof; proces of...
Bacteria or actinomycetales; media therefor
4352536, 435243, 435244, 4352524, C12N 100, C12N 120
Patent
active
055739474
DESCRIPTION:
BRIEF SUMMARY
The object of the present invention is a selective medium for counting or enumerating propionic bacteria.
It also relates to a method for counting these microorganisms.
The propionic bacteria have an essential role in producing the organoleptic characteristics specific to cooked pressed crust cheeses (Emmental-Gruy ere-Comt e). They are involved in the production of CO.sub.2 causing the formation of the "holes", in the production of acetic and, in particular, propionic acids, and in the peptic degradation of milk protein derivatives, both of which contribute to the characteristic flavor.
This bacterial genus has also been used recently for the industrial production of vitamin B.sub.12. Other uses have also been suggested: production of propionates in a bioreactor (French patent n.degree. 90 04 985 publication 2.660.932), said propionates being used for their antifungal properties in bread and cheese making, and production of biomass for probiotic use (feed for milk cows; preservation of silage).
Whether for these uses or for the determination of the role played in the maturing of pressed-crust cheeses, the progress of knowledge on propionic bacteria requires a specific means of counting, that is to say a selective culture medium.
To the knowledge of the applicant, no such selective medium exists.
The reference medium, currently used in the cheese industry, is the YELA (Yeast Extract Lactate Agar) medium described by Hettinga et al., 1968 (J. Dairy Science, 51 1707-1709). This medium enables propionic flora to be counted when they are predominant. However, it does not inhibit the mesophilic and thermophilic lactic bacteria which constitute the dominant flora in cooked pressed crust cheeses.
Two other media, based on the limitation of nitrogenous nutrients (replacement of the yeast extract by ammonium sulfate or a tryptic hydrolysate of casein, trypticase) and the corresponding provision of significant quantities of vitamins (biotin, calcium pantothenate, para-aminobenzoic acid and thiamine) and salts of essential minerals (in particular Mg.sup.++ ; Mn.sup.++ and Fe.sup.++) have been described by Peberdy and Fryer (NZ J. Dairy Science and Techn., 11, 10-15, 1976). These media, named A.S.L.A. (Ammonium Sulfate Lactate Agar) and T.L.A. (Trypticase Lactate Agar), although showing relative selectivity, require at least 10 days anaerobic incubation and in addition must be used in parallel to count the propionic bacteria present in the cheeses. These practical limitations have been considered unacceptable by potential users and the use of the ASLA and TLA media has not developed further.
The addition of cadmium or a mixture of arsenic salts and an antibiotic, netilmicin, to a lactate agar medium (U.S. Pat. 5,026,647) has also been proposed.
However, these media only allow the growth of a limited number of strains belonging to the species P. jensenii and seem to inhibit the other propionic bacteria species.
In addition, the generalized use of these media would obviously create serious toxicity risks both for the operators and for the environment resulting from the discharge of arsenic and cadmium.
The milk propionic bacteria are known to be resistant to the majority of the sulfamides, to some penicillins of the penicillin-M group, such as oxacillin or cloxacillin, as well as to nalidixic acid (Reddy et al; 1972, J. Dairy Sci 55, 665; 1973, J. Milk Food Technol. 30, 564-569; 1973, Antimicrob. Ag. Chemother. 4, 254-258). The same authors have shown that the strains of Propionibacterium tested also showed moderate resistance to polypeptides (colistin and polymyxin B) and to antibiotics of the aminoside group (neomycin and kanamycin). The propionic bacteria are, on the other hand, sensitive to the majority of the .beta.-lactamines (penicillin G and A, cephalosporins) as well as to the cyclines (tetracycline), and to the macrolides, such as erythromycin and to chloramphenicol (Reddy et al., J. Milk Food Technol. 30,564-569; Nord and Olsson-Liljequist, 1985, J. Antimicrob. Chemother., 15, suppl. C, 183-188). As far as th
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Madec Marie-No elle
Maubois Jean-Louis
Rouault Annette
Thierry Anne
Institut National de la Recherche Agronomique
Naff David M.
Ware Deborah K.
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