Effects of two storage β-1,3-glucans, laminaran from Eicenia bicyclis and paramylon from Euglena gracili, on cecal environment and plasma lipid levels in rats

To determine the dietary effects of storage β-1,3-glucans on the intestinal environment, fermentation of laminaran (from brown alga Eicenia bicyclis  , degree of polymerization (DP)≒22), paramylon (granule from Euglena gracilis, DP < 700) and curdlan (from bacteria Alkaligenes faecalis, DP = 2500–4900) by human fecal microflora in vitro was investigated. Furthermore, the dietary effects of 1% (w/w) laminaran and paramylon on the cecal microflora, cecal organic acids and plasma lipid levels in rats were examined. Paramylon suppressed the growth of human fecal microflora in vitro, though laminaran promoted the growth and lowered the pH of the culture medium. Curdlan did not have an effect on the growth and pH. In the rats fed a diet containing laminaran, the cecal weight, cecal organic acids (acetic acid and propionic acid) and ratio of bifidobacteria to total viable cells increased. On the other hand, cecal fermentation was not shown in rats fed paramylon. The diet containing paramylon lowered liver weight, changed the colour of cecal content to green, and increased plasma triacylglycerols. These results indicate that the dietary effects of β-1,3-glucans on intestinal environment and lipid metabolism are affected by molecular weight, DP, and/or solubility in water.