I have tried using MRS broth and plating on MRS agar with 0.01% calcium carbonate and there is bacteria colonies growth on plates. Unfortunately, almost all colonies shows catalase positive which is not belong to lactic acid family. Lactic acid bacteria is catalase negative or is it possible to have a catalase positive lactic acid bacteria?
Hi
The media of Lactic acid bacteria depends on genus of bacteria
Generally, you can use MRS, M17 and Recoze agar but when isolated some genus example Streptococci , you can use Sodium Azid media or Probiotic bacteria, you can use MRS - bile salt .......est
Thanks
Lactic acid bacteria (LAB) are catalase-oxidase negative in general. MRS is usually used to cultivate LAB. In case you got other microorganism on your plate, it is highly suspected that you have contamination and in most cases this contamination is due to either Bacillus spp or other yeasts which can grow also on MRS. You may consider using M17 supplemented with 5% lactose or glucose. Do not use general media ! LAB needs enriched media to grow. In addition, most of G-negative bacteria can not grow on MRS. If you are not happy with MRS and M17, you can use Tryptic Soy broth supplemented with 2% yeast extract.
Keep in mind that it is not as easy as it looks to isolated pure LAB from honey or any other fermented sources.
-Abdelahhad
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