Use of a semi‐continuous culture system (RUSITEC) to study the effect of ph on microbial metabolism of thiamin (Vitamin B₁)

Abstract

Polioencephalomalacia (P.E.M.) in ruminants is often associated with high concentrate diets and rumen acidosis; this syndrome is classically related to a disturbance of the rumen metabolism of thiamin. An in vitro model using a semicontinuous system (RUSITEC) was used to investigate the effect of pH on microbial metabolism and on production of thiamin in the rumen. These effects were tested using either a natural diet (hay/wheat) or a semi-synthetic one. Lowering the pH decreased total volatile fatty acids, methane and microbial nitrogen production. Molar proportions of VFA were modified by an increase in butyric, valeric and caproic acids. Microbial production of thiamin was comparable to in vivo synthesis but decreased when the diet was enriched with thiamin. The diet of the donors of inoculum had no effect on this metabolism. For all diets, lowering of pH did not reduce microbial production of thiamin. Thiaminase activity in the liquid phase of fermentors was very low and was not modified by pH. Thus lowering of pH in vitro, had no deleterious effect on microbial production of thiamin. Therefore, lowering of the rumen pH in acidotic conditions may not be a factor which promotes P.E.M.

Effect of Nitrate Presence on Selenium Bioremediation in Chemically Modified Zeolite Columns

“…However, the pH values in the treated water were reduced, ranging from 6.0 to 6.8. As microorganisms consume the organic compound, which is lactate in the current study, using it as their energy source, they produce metabolic byproducts including volatile fatty acids [37]. These fatty acids are weak acids that can dissociate in water and release hydrogen ions (H + ), thereby lowering the pH of the water.…”

Semicontinuous Culture System for Lemna Gibba Bioassay: Functioning and Theory of Operation

“…Fresh nutrient medium is stored in a container (11). Opening a valve and closing the clamp on the medium line can add medium to the culture vessel.…”

“…The flow rate of the medium is adjusted according to the concentration of the medium and growth rate of L. gibba. If the growth rate is not well calculated or defined, the literature recommends that approximately 20% of culture should be removed as spent and replaced by an equal volume [10,11,16]. Each Lemna growth vessel has an inlet and outlet connection (3 and 4).…”

“…Various strategies, e.g., recharge or buffer system, have been developed. One of such systems is continuous culture, which became widely used particularly for microbes, algae and cell culture for industrial and research purposes [1,7,10,11,30,31]. The early development of the continuous culture system can be traced back to simultaneous works of Novick & Szilard [27] and Monod [25].…”