Characterizing the non-starch polysaccharides of hempseed cell walls

Abstract

Hempseed (Cannabis sativa L.) is a valuable source of oil and a quality vegetable protein source, but little is known about its fiber composition. This study provides the most extensive characterization of hempseed cell wall polysaccharides to date. Quantification of total dietary fiber (TDF) and acetyl bromide soluble lignin (ABSL), monosaccharide composition through two complimentary hydrolysis methods (Saeman hydrolysis and methanolysis), and linkage analysis via derivatization of monosaccharides to partially methylated alditol acetates (PMAAs) were done. More detailed profiling of hempseed xyloglucans and pectic arabinans and galactans was performed via targeted enzymatic generation and quantification of characteristic oligosaccharides. Hempseed’s cell wall polysaccharide profile is consistent with the primary cell walls of dicots, but it is particularly abundant in linear xylans, presumably from secondary cell walls. The hempseed water-insoluble cell wall material was mostly composed of cellulose and xylans, but pectins (including arabinans with a low degree of branching and galactans), xyloglucans with L- and F-motifs and a relatively low substitution rate, and mannans were also present. These data show that hempseed is a good source of complex dietary fiber for human diets and a potential fiber additive for herbivorous livestock diets. Potential consequences of these carbohydrate structural details on hempseed’s microbial fermentability are discussed.