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Ferulic acid esterase activity arose in the ceca of rats that were fed on acid hydrolysate of refined corn bran. The main component of this hydrolysate was soluble ferulic acid arabinoxylan ester. In order to determine the relationship between the ferulic acid esterase activity and intestinal bacteria, the ferulic acid esterase activities from the four kinds of typical bacteria in the intestine were measured. Ferulic acid arabinose ester (LMW) and ferulic acid arabinoxylan ester (HMW) were used as substrates. The enzyme frorn Lactobacillus acidophilus exhibited the highest activity when LMW was used as a substrate. However, when HMW was used, all enzymes from these bacteria exhibited trace activities. At the same time, Blfidobacterium blfidum showed high xylanase and arabinofuranosidase activities. It was suggested that the xylanase and the arabinofuranosidase from bacteria such as B. blfidum attacked HMW and degraded it to lower molecules at first. The ferulic acid esterase from bacteria such as L. acidophilus might then act to release ferulic acid in the cecum.

We compared the effect of direct supplementation with docosahexaenoic acid (DHA) on the fatty acid composition of the liver and the rod outer segment (ROS) membranes of the retina in young (five-week-old) and mature (one-year-old) rats. In young rats, a high content of DHA in the diet (9.7% of total energy) effectively increased the proportion of DHA in ROS membranes (41.8%), compared with the proportion observed in a linoleic acid (LA) diet group (control, 31.6%). The proportion of DHA was also significantly higher in the livers of young DHA-fed rats. These results show that direct supplementation with DHA is very effective in increasing DHA levels in the ROS membranes and livers of developing animals. In contrast, in mature rats there was no significant increase in the proportion of DHA in the ROS membranes, even after the highest dose (8.4% of total energy) of DHA, although the proportion of DHA was significantly higher in the livers of DHA-fed rats. The changes in fatty acid composition in the ROS membranes were different in young and mature rats fed high-DHA diets. Our findings indicate that mature rats maintain a constant level of DHA in the ROS membranes even after being directly supplemented with high doses of DHA.

Enzymatic activities in cecal contents were studied on rats fed on high cholesterol diets with ferulic acid arabinoxylan ester (FAX) and arabinoxylan (AX); both were processed from refined corn bran (RCB) and were compared with those of cellulose(CE)-and RCB-fed rats. The enzymatic activities in the ceca changed according to the diets. Xylanase activity, arabinofuranosidase activity and ferulic acid esterase activity appeared in the cecum of the FAX-and AX-fed rats, but these activities were not observed in the cecum of CE-and RCB-fed rats. FAX and AX showed a tendency to decrease serum cholesterol levels. At first, xylanase and arabinofuranosidase were supposed to attack the FAX and AX main chain and side chain, and thus high molecular weight FAX and AX became lower molecular weight fragments. At that time, ferulic acid esterase was presumed to attack and FAX was degraded lower. These enzymes might act synergistically.

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