Studies On Proliferation Of Kefir-like Grains And Isolation And Identification Of Microorganisms From Them

Activating cultivation and proliferation of a kind of milk ferment calledkefir-like grains were studied. Besides, by morphological characterobservation, physiological and biochemical experiments, somemicroorganisms were preliminarily isolated and identified from thekefir-like grains.When kefir-like grains were subcultured and activated, the vitality ofkefir-like grains gradually increased. At the 7th generation of continuousculture, pH value, whey precipitation percentage and total microorganismsnumber of the fermented milk were respectively 3.97, 51％and 19.18cfu/mL,reached the highest point of kefir-like grain vitality. Afterwards, from the 8thgeneration to the 12th generation, the vitality is basically kept at a high level,when pH value, whey precipitation percentage and total microorganismsnumber of the fermented milk were respectively 4.10, 50％and19.00×10~7cfu/mL.During activating, cleaning to kefir-like grains had some influence on thevitality. Under condition of every generation being cleaned, the vitality ofkefir-like grains rose slower than that of no-cleaning subculture, and at the12th generation, the pH value, whey precipitation percentage and totalmicroorganisms number of the fermented milk were respectively 4.78,43.5％and 9.05×10~7cfu/mL. Under condition of every two generationsbeing cleaned, kefir-like grains also needed be cultivated 10 consecutivegenerations to achieve higher vitality.The proliferation rate of every generation and the total proliferation ratealso had some regularity in activating subculture. From the first generationto the 7th generation, the proliferation rate of every generation was graduallyincreasing and reached the maximum 12％at the 7th generation. Afterwards,from the 9th generation to the 12th generation, it was basically stable at ahigh level of about 9％. The total proliferation rate continued to increasefrom the first generation to the 12th generation, and reached 123.68％at the 12th generation. The results showed that the proliferation rate of everygeneration had a significant correlation with pH value, whey precipitationpercentage and total microorganisms number of the fermented milk,respectively.Cultivated ways had a certain influence on proliferation of kefir-likegrains. Shaking culture was benefit to improvement of the proliferation.After continuous shaking culture of seven generations the proliferation ratewas 2.5 times of static culture.The results of orthogonal test showed that the impact of temperature wasthe most remarkable and the second was inoculation level among the threefactors. The optimum condition of proliferation was culture time of 24 hour,culture temperature of 28℃and 3％of inoculation level. Under the optimumcondition, after three generations culture for activated kefir-like grains, theproliferation rate achieved 105％.Three strains were isolated from kefir-like grains, named M1, M2 and M3.M1, M2 and M3 strains were respectively identified to Saccharomycescerevisiae, Acetobacter aceti and Lactobacillus lactis.