eng Oriental Scientific Publishing Company Biomedical and Pharmacology Journal 0974-6242 2016-08-21 9 2 451 462 10.13005/bpj/958 7917 article Hussah Shafi Al-Otaibi 1 Rukaia Mohammed Gashgari 1 Afrah Eltayeb Mohammed 2 Shaden Abdulmohsen Almojel 3 Mudawi Mukhtar Elobeid 4 Jehan Saud Al Abrahaim 2 Department of Biology, Faculty of Science, King Abdul Aziz Univerisity, Jeddah - Saudi Arabia. Department of Biology, Faculty of Science, Princess Nourah Bent Abdul-Rahman University, Riyadh - Saudi Arabia. Department of Medicin, Faculty of Medicine, Princess Nourah Bent Abdulrahman University, Riyadh - Saudi Arabia. Department of Silviculture, Faculty of Forestry, University of Khartoum, Khartoum north, Shambat – Sudan. In the present investigation five species of probiotic bacteria, whichbelong to Lactobacillus (L. reautari, L. rhamnosus, L. acidophilus),Bifidobacterium(L. casei, L. helveticus, B. bifidum) were evaluated for their growth in dried infant's milk. Three kinds of milk which is used for healthy infants and two other kinds which are widely spread and commonly used for unhealthy breastfeeding infants (vomiting and diarrhea).The study has clearly indicated that all the probiotics employed in this investigation have grown in all milk types to which the nutrient MRS medium was added as well as for the tested milk types without any additives. Findings showed that the optimal time period for adequate growth of probiotic ranges from 12 to 24 hours. Furthermore, it was found that during incubation period of the tested probiotics the pH was in the range of 7.20 to 7.87 for all the milk types tested. It was generally observed that changes in pH were meager during the first 8 hours after incubation and then pH started to decrease reaching a value of ≤ 4 with the increase in growth until the end of incubation period (i-e, 72 hours). The current results also showed that the optimal temperature for adequate growth of probiotics investigated is 37 ºC whereas the least temperature is 5 ºC. Variation in pH had a limiting effect on bacterial growth. Results showed that the best probiotic growth was detected at pH 6 and the least growth was at pH 11. Furthermore, the maximum growth levels at  55% relative humidity, except L. helveticus bacteria for which the highest growth rate was recorded at 75% RH and growth of the tested probiotics was decreased at RH of 35% and 100%. https://biomedpharmajournal.org/vol9no2/investigation-of-the-growth-ability-of-probiotic-lactobacillus-and-bifidobacterium-in-infants-milk-under-different-environmental-conditions/ Probiotic pH  Bifidobacterium Lactobacillus  temperature infant milk