Amino acids and protein metabolism of rumen ciliate protozoa

V. Investigation of artificial buffer solution for cultivation of ciliates

Abstract

Artificial buffer solution and protein-free medium to investigate the endogenous nitrogen compounds of rumen ciliates were tested.
With regard to the tonicity, it was found that concentration of buffer solution equivalent to 0.250M sucrose solution was isotonic to ciliates.
Owing to the intense catabolism of ciliates, pH value of culture medium which had been used widely became extremely low during incubation. To prevent the decrease of pH, the buffer solution having high buffering capacity which maintained pH at 6.4 even after 12hr. incubation was prepared. The buffer solution was called B-9 and its compositions are as follows:
NaCl; 2.6, KCl; 0.2, CaCl2•2H2O; 0.1, MgSO4•7H2O; 0.1, KH2PO4; 2.0, Na2HPO4•12 H2O; 15 (g/l)
The solution was bubbled with mixed gas of N2+CO2 (85:15) and adjusted pH at 6.8.
After 24hr. incubation of ciliates in B-9, organic nutrient-free medium, ciliates maintained active motility and the corpses of ciliates, its fragments and turbidity of the medium were not found.
After 12hr. incubation of ciliates in C2 medium (B-9+glucose, 3g/l+starch, 1.5g/l+cellulose powder, 1.5g/l), pH value was also maintained at 6.3.
Determination of non-protein nitrogen increment in both B-9 and C1 (B-9+glucose, 1g/l+starch, 0.5g/1) medium at every 3 hr. incubation of ciliates showed that their values are constant. Therefore, it seemed to us that the nitrogen compounds excreted even at the first period of incubation might be the endogenous nitrogen compounds upon which food taken previously by ciliates did not influence.