The growth of twelve Lactobacillus strains and six Bifidobacterium strains on a medium containing 13 carbohydrates including prebiotics (fructooligosaccharide (FOS), FOS (Vilof), xylooligosaccharide (XOS), galactooligosaccharide (GOS), short-chain inulin, long-chain inulin, isomalto oligosaccharide (IMO), stachyose, resistant dextrin, polydextrose, L-arabinose, lactitol, and erythritol) as sole carbon sources was compared using lactose as a control. Optical density at 600 nm (OD600 nm) and pH were recorded after 24 and 72 h of culture. Results showed great differences in the growth of strains on different carbohydrates. Resistant dextrin, polydextrose, and erythritol showed very limited growth promotion effects on all the strains after 24 h, probably because these strains lack the enzymes that hydrolyze glycosidic bonds. The growth promotion effects of FOS, XOS, GOS, inulin, stachyose, L-arabinose and lactitol were strain specific, presumably because of the different extracellular or intracellular enzymes secreted by each strain. Long-chain inulin slowed down the fermentation of Lactobacillus acidophilus, but was not applicable to the other strains. Despite being derived from the same source, the FOS from different manufactures showed different effects on the fermentation characteristics of strains, presumably because of the different contents of impurities they had. It was postulated that some prebiotics are beneficial to human health not by directly working on promoting the growth of lactobacilli or bifidobacteria in vivo; instead, they are degraded by other bacteria in the gut before being utilized by probiotic strains.

Lactobacillus acidophilus LA-G80, isolated from the human intestinal flora, has probiotic functions. In this study, the medium composition and culture conditions for this strain were optimized. The results obtained showed that the optimal medium consisted of glucose 41.5 g/L, maltose 20 g/L, soybean oligosaccharide 10 g/L, beef extract powder 18.64 g/L, tryptone 10 g/L, yeast peptone 15 g/L, Tween-80 1 mL/L, K2HPO4·7H2O 2 g/L, NaAc·3H2O 5 g/L, triammonium citrate 2 g/L, MgSO4·7H2O 0.25 g/L, MnSO4·4H2O 0.05 g/L, aspartic acid 0.16 g/L, alanine 0.16 g/L, serine 0.16 g/L, peanut protein powder 5 425 g/L, and soybean cake powder 7 425.48 g/L. The optimal culture conditions were as follows: inoculum size 2%, initial pH 6.0, constant pH 5.5, and constant temperature 37 ℃. Experiments carried out in a 5 L fermenter gave a viable cell count of 42.2 × 108 CFU/mL, which was about 10 times higher than that of observed with MRS medium.

Lactobacillus plantarum is a probiotic bacterium with various biological effects. Its ability to relieve muscle fatigue and injury has aroused market concerns, which is associated with glutamine synthetase (GS) activity. However, the literature currently lacks reports on the production of GS by fermentation with Lactobacillus plantarum. In this study, the GS activity of L. plantarum Lp-G18 was enhanced by adding L-glutamic acid to the medium and optimizing the carbon sources and metal ion concentrations. The optimized medium was composed of glucose 40 g/L (222 mmol/L), MgSO4·7H2O 4.92 g/L (20 mmol/L), MnSO4 0. 025 g/L (1.5 mmol/L), L-glutamic acid 8.82 g/L (60 mmol/L), peptone 10 g/L, beef extract powder 10 g/L, yeast extract powder 5 g/L, K2HPO4 2 g/L, NaAc 5 g/L, diammonium hydrogen citrate 2 g/L, and Tween-80 1 g/L. The GS activity obtained using the optimized medium was 2.4 times higher than that from basal MRS medium.