Fig. 2 Effect of neutral red concentration of fermentation end products by mixed ruminal microbes in vitro.
Although Bauchop (1967) demonstrated that the related dye benzyl viologen decreased methanogenesis by mixed ruminal microbes in vitro, the effects on the amounts and distribution of other end products were not reported.
Fig. 1 Effect of the redox dyes methyl viologen (0.5 mM), neutral red (1 mM) and safranin O (1 mM) on fermentation end product distribution by mixed ruminal microbes in vitro.
With mixed ruminal microbes, rate of substrate disappearance tended to be greater for glucose (GLC) than for PHL and chicory fructan (inulin; INU), which tended to differ from each other (0.74, 0.62, and 0.33 h−1, respectively).
In model rumens, B. thetaiotaomicron BTX increased fiber digestion when added to mixed ruminal microbes, independent of chondroitin sulfate addition; but further study is needed to determine effects on other fiber-digesting bacteria.
Although studies on H2 oxidation coupled to ferric iron reduction by Escherichia coli suggested that NR stimulated both H2 and formate oxidation (McKinlay and Zeikus 2004), NR addition resulted in accumulation of both H2 and formate in our studies with mixed ruminal microbes.
The objective of this in vitro study was to compare the effects of different levels of RDP (0.15, 0.31, 0.46 g of N/L) from tryptone (Tryp) or urea (Ur) on product formation from glucose in fermentations with mixed ruminal microbes.
In agreement with incubations with mixed rumen microbes, glucose release from untreated control lines did not differ from untreated transgenic lines.
The first challenge to produce a bioinoculant using PGPS is to find the best strain of streptomycete (single formulation) or its combination with other microbes (mixed formulation).
In order to avoid contamination of the fermentation process and the product with pathogenic microbes, mixed culture was gradually replaced by pure culture.
