Chitooligosaccharides

Cutting the chain short does not change the chemistry; it changes what happens in a beaker. A chitooligosaccharide is still built from β-(1→4)-linked D-glucosamine and N-acetyl-D-glucosamine units — there are simply two to ten of them rather than several hundred. At that length the chains stop tangling with each other. Intermolecular hydrogen bonding, the force that locks high-molecular-weight chitosan into a semi-crystalline solid which only opens up in dilute acid, loses most of its grip, so a short-chain fraction dissolves in plain water at neutral pH with nothing more than gentle stirring. Viscosity falls at the same time: a one-percent solution flows close to water instead of behaving like a thickener, which is what a formulator wants when the material has to be a minor ingredient rather than the matrix itself.

We work only at the short-chain end of this family, and across its full width. Bulk powder in the low-molecular-weight cuts, single-oligomer reference standards from the dimer to the decamer, fully deacetylated and fully acetylated families alongside partially acetylated ones, membrane-enriched bands for work that cannot tolerate a broad distribution, and the amino sugars sitting underneath the ladder. Chain length, acetylation pattern and counter-ion are the three variables a batch is built around here, and all three can be specified.

What the term covers, and where its edges fall

Two ways to shorten the chain, and why the route shows up in the product

Acid hydrolysis is the blunt instrument. Chitosan is held in concentrated hydrochloric acid at elevated temperature — roughly 35% HCl at 80 °C for one to two hours is the condition most often quoted — and the glycosidic bonds break more or less at random. The reaction is hard to steer, the fragments spread over a wide range of lengths, and the acid has to be washed out afterwards. Enzymatic hydrolysis behaves in the opposite way. Chitosanase (EC 3.2.1.132) and chitinase (EC 3.2.1.14) cut β-(1→4) linkages specifically, at moderate temperature and close to the enzyme optimum pH, so the band you end up with is set by enzyme dose, substrate ratio and time rather than by luck.

Enzymatic depolymerisation under controlled temperature — the route that keeps the chain-length band narrow.

Reading a quotation from this family

The ladder, rung by rung

Single oligomers are normally supplied as hydrochloride salts, because the free-amine form is hygroscopic and awkward to weigh accurately. The series below is what we keep in stock; every rung can be supplied from a few milligrams up to multi-gram quantities.

Three acetylation families, not one

Chain length is only half of a batch's identity. The acetyl groups still attached to the chain change the charge density unit by unit, and the way they are distributed along the oligomer — the pattern of acetylation — is a variable in its own right. Material from a straight acid or enzyme hydrolysis usually carries a random pattern. Where a project depends on the arrangement, the pattern can be steered by combining a chitin oligosaccharide deacetylase with the depolymerising enzyme, and then proven rather than assumed.

Molecular-weight cuts for volume work

Most projects do not need a single species. Bulk material is supplied as a defined molecular-weight window, and the window determines how the powder behaves once it is in solution. Four standard cuts sit on the shelf; narrower ones are produced by membrane fractionation to order.

Collecting the separated fractions: a mixed hydrolysate being split into defined molecular-weight windows.

Standards, kits and substrates

Analytical work needs the single species, not the mixture, so this part of the range is built around small vials and documents rather than drums. Every lot leaves with its chromatographic and spectral data attached.

How a batch is characterised

An average molecular weight hides a distribution, and two powders with the same average can behave quite differently. We report the distribution itself, using whichever of the following methods suits the question being asked.

Reading the oligomer distribution of a finished batch from a mass spectrometry target plate.

Getting it into solution, and keeping it there

• No acid step. At this chain length the powder dissolves in water at room temperature with gentle stirring, and nothing has to be added beforehand. That is the practical difference from polymer-grade chitosan, which needs dilute acid to open up before it will go into solution at all.
• Expect a mildly acidic solution. A one-percent solution typically lands between pH 4.5 and 7.0, depending on how many acetyl groups remain and on the counter-ion, so measure it after dissolution rather than assuming a figure.
• Water is the solvent; ethanol, propanol and the other alcohols are not. Where a co-solvent is needed for a longer partially acetylated member, dissolve the solid in water first and add the alcohol afterwards.
• Order of addition matters in formulations. Dropping the solid into a dilute solution of an anionic polymer will find the two complexing on the spot; add the oligosaccharide solution last, under good agitation, if a clear system is the goal.
• Store sealed, cool, dry and out of direct light. Solutions are best used fresh; where one has to be kept, freeze it or dry the material back down rather than holding it as a liquid at room temperature.
• Two conditions to avoid: prolonged heat and strongly alkaline media. Both push the short chains back toward polymer behaviour and darken the powder along the way.

The whole proposition in one frame: powder going into plain water and dissolving without an acid step.

Where short chains are actually used

Assay work: clearing zones in a chitin gel plate, the classic readout for chitinase or chitosanase activity.

Adjusting a batch, and scaling it

Nearly every project starts from one of the standard cuts and then moves. These are the levers we can pull, individually or together.

• Chain length: DP-enriched fractions separated by membrane or chromatographic methods, from a two-oligomer band up to a broad technical cut.
• Acetylation: fully deacetylated, partially acetylated or fully acetylated, with the pattern itself specified where an application depends on it.
• Counter-ion: hydrochloride, acetate or lactate, whichever sits better with the rest of the formulation.
• Purity: standard grade through to material intended for analytical work, with lot-specific chromatograms and spectra attached.
• Pack size: from 5 mg reference vials up to 25 kg drums, foil-lined for bulk consignments.
• Paperwork: a certificate of analysis and a safety data sheet with every shipment, and retention samples kept against the batch number for traceability.
• Matched supply: send the specification you already buy against, and we will quote to that rather than asking you to redesign around whatever happens to be in stock.

Bulk consignments leave in sealed drums with the batch documentation attached.

Picking a starting point

Most first orders come down to one of the rows below. Where the requirement is not on the list, describe the experiment rather than the product — the fraction that fits and what it will look like on a specification sheet is a short conversation.

For Research or Industrial Raw Materials, Not For Personal Medical Use!