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cyclodextrin

cyclodextrins are cyclic oligosacharides produced from starch. The most well known representatives are built up from 6, 7, or 8 glucopyranose units called alpha-, beta- and gamma-cyclodextrins. The hydroxyl groups located at the rim of the ring ensure good water solubility. The inner side of these ring-shaped molecules is rather hydrophobic resulting in inclusion complex forming ability: guest molecules of poor solubilitycan enter the cavity of the host cyclodextrins. The solubility of the poorly soluble guest molecules is usually improved by complex formation. This solubilizing effect can be observed especially for the cyclodextrin derivatives of high solubility, like hydroxypropyl cyclodextrin (HPBCD) and random methylated cyclodextrin (RAMEB). Both are produced on ton scale. Pharmaceutical excipients and food additives. They are non-toxic. The alpha- and gamma-cyclodextrins can be consumed without any restrictions, the acceptable daily intake (ADI) for beta-cyclodextrin is 0.5 mg/kg, that is a person of 50 kg can consume 25 mg a day. The environmental application of cyclodextrins is based on their complex forming ability towards most of the organic contaminants. For example, the contaminants having low solubility, high Kow and high sorption to the soil (that is low bioavailability) will show improved availability on the effect of cyclodextrin complexation. The efficiency of the remediation technologies especially that of the bioremediation technologies can be enhanced by cyclodextrins as additives. cyclodextrins, as environmentally friendly materials can substitute the harmful tensides.

Cyclodextrin Technology
abbreviated as CDT, a bioremediation technology utilizing cyclodextrin (more exactly random methylated beta-cyclodextrin) for improving the bioavailablitity of the organic contaminants e.g. hydrocarbons, PAHs, chlorinated aliphatic hydrocarbons, polychlorinated biphenyls (PCBs) in the soil. The time saving by the cyclodextrin-intensified bioremediation may compensate for the higher price of the technology. Further details can be found in MOKKA database (sheets No. 51 and 175). Further literature: Gruiz, K.; Fenyvesi, E.; Kriston, E.; Molnar, M.; Horvath, B. (1996) J. Inclusion Phenom. Mol. Recognit. Chem. 25(1-3), 233-236, Leitgib, L.; Gruiz, K.; Fenyvesi, E.; Balogh, G.; Muranyi, A. (2008) Science of the Total Environment, 392(1), 12-21
hydroxypropyl beta-cyclodextrin
abbreviated as HPBCD, a sugar derivative of good solubilizing capacity. By molecular encapsulation (inclusion complex formation) it can dissolve water-insoluble organic compounds, e.g. hydrocarbons in water. It is of ring shape molecule, a cyclodextrin unit with 3-6 hydroxypropyl substituents. It is utilized for mobilizing the organic pollutants in soil (→"sugar flushing" technology), for improving the bioavailability and biodegradability of these contaminants. HPBCD is fast biodegraded in soils (half life time is < 1 year). It is not harmful for the soil microflora, improves the availability of their nutrients. It is harmless for the humans as well, is used as pharmaceutical excipient and as an additive in various food products.
random methylated beta-cyclodextrin
a cyclodextrin derivative containing 12 methyl groups in average in a molecule in a random pattern. Similarly to tensides it has good solubilizing effect therefore utilized for solubilization, mobilization of soil contaminants and for the improvement of their bioavailability. Its solubilizing capacity is usually higher than that of the hydroxypropyl beta-cyclodextrin, but its biodegradation in the soil is slower (the half life time in the soil is 1-1.5 year). It is not harmful for the soil microflora, it has rather a beneficial effect by improving the availability of the nutrients of the microbes. It is harmless for humans as well, used as excipient in drugs, cosmetics and foods.