Corn starch was better both in the amount of bacteria attached per unit weight of starch and in easiness of handling than other starches from different origin as adsorbent for bacterial attachment. The attachment of bacteria to starch occurred shortly after the addition of starch granules, and a maximum attachment was attained after further 5-min incubation at 38°. The amount of bacteria attached to starch granules was approximately proportional to the quantity of granules added until 2.5% in weight per volume.
Effect of environmental factors on the attachment of rumen bacteria to starch was examined. The attachment of bacteria to starch was maximal in a medium containing sodium carbonate above 0.15%. Carbon dioxide as gas phase was far better in the attachment of bacteria to starch than hydrogen and nitrogen gases. There existed bacteria capable of attaching to starch even at 4° or for the first time at above 30°. The amount of bacteria attached to starch was small at 4° and more abundant at 38°.
A trial was made to elute bacteria attached to starch granules first with a salt solution and subsequently with Formalin. The results obtained showed that bacteria attached to starch, excepting those attached at 4°, included the following three types of bacteria. The bacteria of thefirst type were those loosely attaching to starch, that were eluted easily with a salt solution. The bacteria of the second type were those firmly attached and were eluted for the first time with Formalin. The bacteria of the third type were those with irreversibly attaching ability, that were not eluted even with Formalin.
The most characteristic properties of bacteria attached to starch were their amylase and urease activities. The specific amylase activity of bacteria attached to starch was remarkably high, compared with that of non-attached bacteria. There was little or no specific urease activity of attached bacteria, while that of non-attached bacteria was relatively high. There was no significant difference in the specific activity of other four hyrolases between bacteria attached and non-attached to starch.
The actual role of bacteria which are apt to attach to starch in the rumen
in situ is also discussed.
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