Inulin backbone

Inulin is characterized by a p-(2—>1) linked backbone and is generally found as reserve carbohydrate in plants such as chicory (up to 20%), Jerusalem artichoke, and onion, and also in some bacteria. Plant inulin has a degree of polymerization (DP) with a maximum up to 200, which depends on the plant species and their life-cycle. Bacterial inulin has a much higher DP (from 10,000 to more than 1(X),000) but is also highly branched (>15%). Both DP and the presence of branches are important properties since they influence the functionality of the inulin. Many possible applications demand a high molecular weight inulin like bacterial inulin, but without branches. 

Inulin. Fructans are natural polymers of fructose. In nature, there are two different types of fructans. One is named levan with a backbone of (3-(2 6)... 

Pectin, amylose, dextran and inulin provide coatings that degrade by enzymes of colonic flora. These polysaccharides are commonly combined with cellulose ethers or esters or synthetic polymers to obtain biphasic release profiles or colon-specific release [29-31]. Drugs conjugated to dextran (linear polymer backbone of a-D-glucopyranose units) show enhanced stability in the upper part of the gastrointestinal tract, but they can be absorbed in the colon [32]. 

As an answer to the growing demand for products made from renewable resources and with (modified) starch as a reference in mind, a lot of these starches have been devoted to the chemical modification of inulin [3]. Hydrophobization of inulin, e.g. grafting of alkyl chains on to the inulin backbone and as such obtaining an inulin derivative showing the wanted amphiphilic character, can be done in several ways by esterification, by etherification or by carbamoylation. The reactions are usually performed in solvents like pyridine, dimethylformamide or dimethylsulfoxide, using catalysts like, for example, sodium acetate, potassium carbonate or triethylamine. 

Different HMI surfactants can be obtained by changing three parameters the DP of the inulin backbone, the length of the alkyl chain and the degree of substitution. INUTEC SP1, commercially available from BENEO Bio Based Chemicals, consist of an inulin backbone with a DP greater than 23 on which several Cn alkyl chains are randomly grafted. 

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