Isolation and Identification of Lactobacillus Strains from Dairy Products and Evaluation of Carbon Sources Effects on Bacterial Growth and Phytase Activity: Supplement for Fish Feed

Lactobacillus sp. are safe organisms for using as probiotic due to their different properties such as useful enzyme products. For example, phytase is an enzyme that has an important role in fish feed digestion. The aim of this study was to isolate and identify Lactobacillus species with phytase activity from dairy products such as milk, yogurt, and cheese and to evaluate the effects of different carbon sources on bacterial growth and phytase activity. For this purpose, Lactobacillus species were screened from dairy products using biochemical tests, and 16S rRNA gene analysis was used to confirm the lactobacilli class. Three of the isolates that showed the best bacterial growth and phytase activity were selected and their 16S rRNA gene sequences were deposited in GeneBank. Then, to determine the optimum growth conditions, three carbon sources including glucose and sucrose at concentrations of 10, 20, 30, 40 g L-1 and wheat bran at concentrations of 10, 20, and 30 g L-1 were used in three replicates. Phytase activity of isolated bacteria including Lactobacillus sp. strains AM11, AM13, and AM14 were measured using zymoplate as well as extracellular enzyme assay. Lactobacillus sp. strain AM11 showed higher phytase activity and growth compared to the other isolates (P<0.05). According to the results, Lactobacillus sp. strain AM11 isolates can be used as a feed supplement to improve minerals availability in fish nutrition.