Biotechnology and Bioprocess Engineering 19: 58-69 (2014) DOI 10.1007/s12257-013-0488-9 New Chitin, Chitosan, and O-Carboxymethyl Chitosan Sources from Resting Eggs of Daphnia longispina (Crustacea); with Physicochemical Characterization, and Antimicrobial and Antioxidant Activities Murat Kaya, Yavuz Selim Cakmak, Talat Baran, Meltem Asan-Ozusaglam, Ayfer Mentes, and Kabil Ozcan Tozak Received: 26 July 2013 / Revised: 22 October 2013 / Accepted: 27 October 2013 © The Korean Society for Biotechnology and Bioengineering and Springer 2014 Abstract The paper describes the isolation and charac- terization of chitin and chitosan from Daphnia longispina resting eggs harvested from a reservoir. Resting eggs are fertilized eggs that are encased in chitinous shells called ‘ephippia’ and which ensure the survival of the Daphnia population in adverse conditions. The chitin-content of D. longispina resting eggs was found to be 23 ~ 25% and the chitosan (having a 70 ~ 75% deacetylation degree) yield of the chitin was 76 ~ 77%. This high chitin-content indicates that D. longispina resting eggs can be exploited as a chitin source. The structure and thermal properties of chitin, extracted from D. longispina resting eggs, were characterized by employing Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. The crystallinity of the chitin was found to be very low (48%). Physicochemically- characterized chitosan and the produced O-carboxymethyl chitosan were tested for their antimicrobial and antioxidant activity. It has been observed that chitosan displays antimicrobial activity against all pathogenic bacteria, whereas O-carboxymethyl chitosan only exhibits inhibition activity against L. garvieae, L. Monocytogenes ATCC 7644, Y. enterocolitica NCTC 11175 and S. aureus ATCC 25923. In a free radical scavenging activity assay, the IC 50 values of chitosan, O-carboxymethyl chitosan and butylated hydroxy- toluene were found to be 23.01, 56.43 and 0.05, respectively. The ferric-reducing power of O-carboxymethyl chitosan (EC 50 = 8.30) indicated higher activity than chitosan (EC 50 = 10.12). Keywords: chitin, chitosan, O-carboxymethyl, physico- chemical characterization, biological activity 1. Introduction Studies on the production and characterization of chitin and chitin-derivatives have generally focused on crab, shrimp and krill [1,2]. In recent years, chitin has been isolated from some species of insects [3-5] and fungi [6], and their characterization has suggested alternative sources of chitin. In chitin production, adult organisms that belong to the Crustacea group are generally selected, but in only one research, chitin-content of Artemia cyst structure was examined and suggested as a new source of chitin [7]. Chitin and its derivatives are used in various fields, such as agriculture, food preservation, drug delivery, tissue engineering, wastewater treatment, molecular imprinting and cosmetics [8-10]. Studies focusing on chitin and its derivatives are increasingly numerous, and new potential areas of usage have been determined [11-13]. In the current study, and in order to contribute to the increasing need for chitin worldwide, the potential use of D. longispina resting eggs as an alternative source for chitin has been investigated. Daphnia are predominantly small, freshwater crustacean zooplankton and forms, as such, an essential part of the Murat Kaya, Yavuz Selim Cakmak, Asan-Ozusaglam Department of Biotechnology and Molecular Biology, Aksaray University, Aksaray, Turkey Murat Kaya * , Yavuz Selim Cakmak, Talat Baran, Meltem Asan-Ozusaglam, Ayfer Mentes Science and Technology Application and Research Centre, Aksaray University, Aksaray, Turkey Tel: +90-382-228-2184; Fax: +90-382-288-2185 E-mail: muratkaya3806@yahoo.com Talat Baran, Ayfer Mentes, Kabil Ozcan Tozak Department of Chemistry, Faculty of Science and Letters, Aksaray University, Aksaray, Turkey RESEARCH PAPER