Microbial fermentation of starch- or fibre-rich feeds added with dry or pre-activated Saccharomyces cerevisiae studied in vitro under conditions simulating high-concentrate feeding for ruminants.

BACKGROUND: To study if the effect on fermentation of yeasts added in ruminant diets can be improved, the effect of adding dry (DY) or pre-activated (AY) Saccharomyces cerevisiae, compared with unsupplemented rumen fluid (CT), on barley grain or sugar beet pulp was evaluated under in vitro high-concentrate fermentative conditions. Yeasts were pre-activated by culturing aerobically at 30 °C for 24 h. RESULTS: In Experiment 1, AY showed a higher concentration than DY at 6 h incubation (6.83 versus 5.76 log cfu mL-1 ; P = 0.007), differences disappearing at 12 h. This was supported by higher gas production with AY, especially on sugar beet pulp. In Experiment 2, incubation pH was 6.24 and 6.31 respectively for barley and sugar beet pulp at 8 h (P < 0.05), but no effect was recorded at 24 h (6.00 and 5.96; P > 0.05). With sugar beet pulp, gas production promoted by AY was the highest (P < 0.05) in the first 8 h of incubation. However, differences with barley were lower and only detected between AY and CT at 12 h (P < 0.05). Total volatile fatty acids (VFAs) concentration at 8 h followed the same trend, but no differences were detected on molar VFAs profile or lactate concentration. Microbial diversity was more affected by the incubation series than by experimental treatments, and inocula including yeasts (AY, DY) did not differ from unsupplemented rumen liquid. CONCLUSIONS: When pre-activated, the concentration of S. cerevisiae was initially higher and resulted in higher gas volumes, and more on a fibrous (sugar beet pulp) than a starchy (barley) substrate. The response is apparently quantitative, since no major changes were detected on biodiversity or fermentation profile. © 2020 Society of Chemical Industry.

Improving the antiprotozoal effect of saponins in the rumen by combination with glycosidase inhibiting iminosugars or by modification of their chemical structure.

The antiprotozoal effect of saponins is transitory, as when saponins are deglycosylated to sapogenins by rumen microorganisms they become inactive. We hypothesised that the combination of saponins with glycosidase-inhibiting iminosugars might potentially increase the effectiveness of saponins over time by preventing their deglycosylation in the rumen. Alternatively, modifying the structure of the saponins by substituting the sugar moiety with other small polar residues might maintain their activity as the sugar substitute would not be enzymatically cleaved. The aim of this in vitro study was to evaluate the acute antiprotozoal effect and the stability of this effect over a 24 h incubation period using ivy saponins, a stevia extract rich in iminosugars, ivy saponins with stevia extract, and a chemically modified ivy saponin, hederagenin bis-succinate (HBS). The effects on fermentation parameters and rumen bacterial communities were also studied. Ivy saponins with stevia and HBS had a greater antiprotozoal effect than ivy saponins, and this effect was maintained after 24 h of incubation (P<0.001). The combination of ivy and stevia extracts was more effective in shifting the fermentation pattern towards higher propionate (+39%) and lower butyrate (-32%) and lower ammonia concentration (-64%) than the extracts incubated separately. HBS caused a decrease in butyrate (-45%) and an increase in propionate (+43%) molar proportions. However, the decrease in ammonia concentration (-42%) observed in the presence of HBS was less than that caused by ivy saponins, either alone or with stevia. Whereas HBS and stevia impacted on bacterial population in terms of community structure, only HBS had an effect in terms of biodiversity (P<0.05). It was concluded that ivy saponins with stevia and the modified saponin HBS had a strong antiprotozoal effect, although they differed in their effects on fermentation parameters and bacteria communities. Ivy saponins combined with an iminosugar-rich stevia extract and/or HBS should be evaluated to determine their antiprotozoal effect in vivo.

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Three new norditerpenoid alkaloids from Consolida orientalis.

The structures of three new norditerpenoid alkaloids named dehydrodeltatsine (1), 14-O-acetyltakaosamine (2), 18-demethoxypubescenine (3) isolated from the aerial parts of Consolida orientalis (GAY) SCHROD., were elucidated by 1D and 2D NMR spectroscopy and HR-EIMS. Twelve known norditerpenoid alkaloids (type lycoctonine) and the diterpenoid alkaloid ajaconine have been isolated. Several assignments of (13)C-NMR data for delbonine (4) were revised and the complete assignment for 18-hydroxy-14-O-methylgadesine (5) was realized.

Four new alkaloids from Consolida glandulosa.

The structures of four new hetisine-type diterpenoids, 9-deoxyglanduline (1), glandulosine (2), 11,13-O-diacetylglanduline (3), and 9-O-acetylglanduline (4), isolated from Consolida glandulosa, were determined by two-dimensional NMR techniques. All the structures of these compounds were substantiated by a single-crystal X-ray analysis performed on compound 3.

Alkaloids from Consolida oliveriana.

Four new diterpenoid alkaloids, olivimine (1), olividine (2), 8-O-methylcolumbianine (3), and 7alpha-hydroxycossonidine (4), were isolated from the aerial parts of Consolida oliveriana. Compounds 1 and 2, 3, and 4 belong to the lycoctonine-azomethine, aconitine, and hetisine types, respectively, and their structures were elucidated by spectral data interpretation.