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We screened lactic acid bacteria that exhibited high innate immunity-stimulating activity by monitoring muscle contraction activity in silkworms. Heat-treated fractions of lactic acid bacteria, Leuconostoc carnosum #7-2, Leuconostoc gelidum #4-2, and Leuconostoc mesenteroides 8/11-3, had high (250-460 units/mg) innate immunity-stimulating activity. These lactic acid bacteria proliferated in milk to concentrations of 1 × 106 colony forming unit/mL. The present findings suggest that the silkworm muscle contraction assay is useful for screening lactic acid bacteria with high innate immunity-stimulating activity, and that the assay can be used for the production of fermented foods made from milk. [ABSTRACT FROM AUTHOR]

This study performed an acute oral toxicity test of 59 compounds in silkworms. These compounds are listed in OECD guidelines as standard substances for a cytotoxicity test, and median lethal dose (LD50) werecalculated for each compound. Acute oral LD50 values in mammals are listed in OECD guidelines and acute oral LD50 values in silkworms were determined in this study. R2 for the correlation between LD50 values in mammals and LD50 values in silkworms was 0.66. In addition, the acute oral toxicity test in silkworms was performed by two different facilities, and test results from the facilities were highly reproducible. These findings suggest that an acute oral toxicity test in silkworms is a useful way to evaluate the toxicity of compounds in mammals. [ABSTRACT FROM AUTHOR]

Lactic acid bacteria (LAB) have been thought to be helpful for human heath in the gut as probiotics. It recently was noted that activity of LAB stimulating immune systems is important. Innate immune systems are conserved in mammals and insects. Silkworm has innate immunity in response to microbes. Microbe-associated molecular pattern (ex. peptidoglycan and β-glucan) induces a muscle contraction of silkworm larva. In this study, we established an efficient method to isolate lactic acid bacteria derived from natural products. We selected a highly active LAB to activate the innate immunity in silkworm by using the silkworm muscle contraction assay, as well. The assay revealed that Lactococcus lactis 11/19-B1 was highly active on the stimulation of the innate immunity in silkworm. L. lactis 11/19-B1 solely fermented milk with casamino acid and glucose. This strain would be a starter strain to make yogurt. Compared to commercially available yogurt LAB, L. lactis 11/19-B1 has higher activity on silkworm contraction. Silkworm normally ingested an artificial diet mixed with L. lactis 11/19-B1 or a yogurt fermented with L. lactis 11/19-B1. Interestingly, silkworms that ingested the LAB showed tolerance against the pathogenicity of Pseudomonas aeruginosa. These data suggest that Lactococcus lactis 11/19-B1 would be expected to be useful for making yogurt and probiotics to activate innate immunity. [ABSTRACT FROM AUTHOR]

Vegetables are eaten as part of a healthy diet throughout the world, and some are also applied topically as a traditional medicine. We evaluated the innate immunostimulating activities of hot water extracts of various vegetables using the silkworm muscle contraction assay system, and found that broccoli, Brassica oleracea var. italica, contains a strong innate immunostimulant. We purified the innate immunostimulant from broccoli, and characterized the chemical structure by chemical analyses and NMR spectroscopy. The innate immunostimulant comprised galacturonic acid, galactose, glucose, arabinose, and rhamnose, and had a pectic-like polysaccharide structure. To determine the structural motif involved in the innate immunostimulating activity, we modified the structure by chemical and enzymatic treatment, and found that the activity was attenuated by pectinase digestion. These findings suggest that a pectic-like polysaccharide purified from broccoli has innate immunestimulating activity, for which the polygalacturonic acid structure is necessary. [ABSTRACT FROM AUTHOR]

Leuconostoc carnosum #7-2, L. gelidum #4-2, and L. mesenteroides 8/11-3, which were isolated from fermented plant foods, are lactic acid bacteria. We previously reported that these bacteria are functional lactic acid bacteria whose innate immunity-stimulating activities are high based on a silkworm muscle contraction assay. The concentrations of these three lactic acid bacteria increased to more than 1 × 106 colony forming units (cfu)/mL in various vegetable and fruit juices when the pH values were appropriately adjusted. As the bacteria grew in the vegetable and fruit juices, the pH decreased and the concentrations of total sugars and glucose also decreased. These findings suggest that these functional lactic acid bacteria can be used to produce vegetable and fruit juices with reduced sugar levels, which is expected to be beneficial for human health. [ABSTRACT FROM AUTHOR]