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The polysaccharide chitin is widely distributed in the biosphere and, like cellulose, it is a highly abundant biopolymer available from renewable resources.1 The annual regeneration of chitin by biosynthesis is even higher than that of cellulose.2–4 The principal source for production of chitin is waste from processing of shrimp and other crustaceans, estimated to be in the order of 106 tons per annum,5 with chitin content between approximately 10 and 30% of dry matter. However, the industrial demand for chitin was estimated in 2000 to be only about 10,000 metric tons per annum which is about four orders of magnitude lower than that for cellulose. Most of the chitin is hydrolyzed for production of glucosamine.6 The demand for chitosan, which is the deacetylated, cationic derivative of chitin, is estimated to be around 2,000 metric tons per annum.

The unique, amply documented physicochemical and biomedical properties of chitosan render it a formidable biopolymer, much too precious to be dumped as waste into the sea or in landfills. The reluctance of the industry to explore chitosan is due mostly to uncertainties and limitations in availability of bulk quantities, in addition to higher costs of production of good quality materials. In consequence, research on chitosan must focus on unique, high-value applications, exploring niches in the high-tech and health industrial sectors.

The global research activity and progress in chitin science is reflected not only by the number of patents and publications in journals, but also by conferences organized at regular intervals by a number of Chitin Societies, either as Regional events (Asia-Pacific, Europe, Ibero-America, Canada-USA), as well as National meetings (India, Japan, Korea, Poland, PR China, Russia, Taiwan, Thailand, Vietnam), often in conjunction with International World Conferences on Chitin and Chitosan. Proceedings are often published in a non-peer reviewed series of books, known as “Advances in Chitin Science”.

This Special Issue of Polymer International contains a collection of three reviews and 12 research papers presented at the 5th Symposium of the Sociedad Iberoamericana de Quitina (SIAQ), Santiago do Chile, June 06–09, 2010. Around 90 delegates attended the conference, 29 of them were students. Besides members of SIAQ, i.e. from the Latin Americas, Portugal, and Spain, a few participants came from other European countries and also from Asia. The scientific programme included six plenary lectures, 23 oral presentations and 111 posters, documenting the lively scientific activity of SIAQ. Topics were divided into the thematic areas production, enzymes, and applications in various areas, including nanotechnology and biomaterials. Besides inviting three reviews, all participants were encouraged to submit extended abstracts of their work for evaluation by a board of reviewers which assembled during the conference.

Properties of composites prepared from bacterial or nanofibrillated cellulose and chitosan are reviewed by Fernandes et al.7 This paper presents some novel aspects on the macromolecular assembly, using fluorescent chitosan derivatives. The composites possess unique barrier, mechanical, antimicrobial, and optical properties, besides improved printability, making them especially interesting for packaging and electronic devices. A short section deals also with the preparation and properties of oxypropyl-chitosan, which offers new venues for the construction of novel graft polymers.

Peniche and Peniche8 present a review of the state of the art of the preparation of nanoparticles from chitosan and their applications in pharmacological drug delivery, including oral, nasal, pulmonary, and ocular administration routes as well as delivery of vaccines and gene therapy.

A timely review by Ubhayasekera9 on the structures, mechanisms, and functions of a group of chitinases, known as family 19 glycosyl hydrolases10 is presented here. Despite their potential use for depolymerization of chitin and their role in plant defence responses, relatively little is known on the family 19 members, as compared with their family 18 relatives.

Production of chitosan and derivatives with control of degree of acetylation (FA), molecular weight (DP, Mw or Mv) and dispersity Ð can still be improved by process optimization. The kinetics of depolymerization of chitosan under sonolysis, microfluidization, and shear at various concentrations and reaction temperatures is investigated by Chen et al.11 who propose a novel protocol for control of the process for production of chitosan with low PI. Ultrasound-assisted deacetylation of β-chitin gives a rather high Mv and low FA chitosan (Delezuk et al).12N-Permethylation of chitosan with dimethylsulfate is optimized by factorial design with variation of reaction time and temperature (Britto et al).13

Polyelectrolyte complexes (PEC) of chitosan and blends with other macromolecules continue to attract interest due to their potential for pharmaceutical and food applications. Ramos-de-la-Peña et al14 characterize PEC prepared from water soluble chitosan at various concentrations and Jicama pectin, a low-methoxylated anionic polysaccharide with considerable economical importance, while Horn et al15 study the physicochemical properties of chitosan blends with gelatinized and with chemically modified starch. Aldehyde groups introduced into starch by periodic acid oxidation may condense with amino groups of chitosan, thus giving a novel type of cross-linked polymer. Ezquerra-Brauer et al16 blend collagen from jumbo squid with chitosan and report on barrier, mechanical, and thermal properties of films. This paper is also interesting because the collagen originates from waste of a marine organism that has significant economic importance for the seafood industry in the Baja Californica regions of Mexico.

Coming now to applications, articles dealing with food storage, pharmaceutical, and technical aspects are included in this Special Issue. Assis and Britto17 use a common document scanner for digital image processing of apple slices to quantify the antifungal effects of chitosan coating, while Cota-Ariolla et al.18 report that chitosan inhibits growth of Aspergillus parasiticus in culture, but does not reduce aflatoxin levels in corn grain. Incorporation of iron oxide into quaternized chitosan presents a novel contrast agent for magnetic resonance imaging (Shen et al).19 A sensitive detector for ppm concentrations of H2S is constructed by incorporation of suitable indicator dyes into chitosan films (Kato et al).20 Composites made from CaO and chitosan are efficient catalysts for production of biodiesel by transesterification of soybean oil with methanol (Fu et al).21 Last but not least, coating of Kraft paper with chitosan improves the mechanical and barrier properties of the inexpensive, widely used packaging materials (Reis et al).22

In summary, besides contributions from Portugal, Sweden, and Taiwan, this collection of reviews and research papers presents several nice examples of research activities on chitosan in South-and Central America. We are thankful to all authors for submitting their work for publication in this issue. We also wish to express our thanks to the editors of Polymer International for accepting our proposal to publish a Special Issue on “Advances in Chitin and Chitosan Research”, as well as for their encouragement, guidance and help in assembling the articles.

Acknowledgements

  1. Top of page
  2. Acknowledgements
  3. REFERENCES

The Guest Editors would like to thank the following for their assistance in processing and selecting papers for this special issue:

  • Guest Editorial Board:

  • S. Campana-Filho, Universidade de São Paulo, São Carlos, Brasil

  • G. Cárdenas, Universidad de Concepción, Chile

  • R.-H. Chen, Seaparty International Co., Keelung, Taiwan

  • A. Gandini, Universidade de Aveiro, Portugal

  • M. Plascencia-Jatomea, Universidad de Sonora, Mexico

  • S. M. Rodríguez, Universidad Nacional del Sur, Bahia Blanca, Argentina

REFERENCES

  1. Top of page
  2. Acknowledgements
  3. REFERENCES