Influence of the drying route on the depolymerization and properties of chitosan

Abstract

In this work, a chitosan sample with a high degree of deacetylation (DD >95%) obtained from freshwater shrimp shells was subjected to drying processes in an electric oven and by supercritical CO2. The results indicated that drying chitosan particles with supercritical CO2 resulted in a very significant increase in specific surface area and pore volume, and also increased the material's crystallinity index. This drying route led to a more than 10‐fold reduction in viscosimetric molecular weight (from 35.3 to 3.0 kDa), indicating that the physical drying process caused the chitosan to depolymerize, which usually occurs by enzymatic and chemical methods, according to the literature. Low molecular weight chitosan is essential for some applications in the field of biomedicine (drug delivery for example); hence, drying via the CO2 route can be considered a promising technique for the production of high value‐added materials with applications in this area. POLYM. ENG. SCI., 55:1969–1976, 2015. © 2014 Society of Plastics Engineers

Effect of shrimp shells milling on the molar mass of chitosan

“…In an earlier work [1] , when using reflux for 10 hours at 100 °C in 50% of NaOH solution, chitosan was obtained whose DD ranged between 95 and 97%. When performing the adaptation for this simplified method and stirring under room temperature, DD values obtained by 1 H NMR (Figure 4) located between 77 and 80% (Table 1) demonstrate the viability of this method when the DD range is suitable for the intended purpose of chitosan produced.…”

“…where K and α are constants for a given polymer-solvent system, which in the case of chitosan, varies according to the degree of acetylation (DA) [16] . Chitin extraction was confirmed by determining the rates of demineralization and deproteination, and the average degree of acetylation of chitosan was obtained by 1 H NMR, using a Bruker Avance III spectrometer and 9.4 Tesla, in the following experimental conditions: 400 MHz for hydrogen frequency (SWH), experimental temperature of 323 K, 16 scans (ns), wait time of 10 s (d1), acquisition time of 6.83 s (aq), and 65,536 data points (td). The %DA and %DD were calculated as described by Santos et al [20] .…”

“…In a previous work, our group evaluated the influence of different drying routes over depolymerization and properties of the biopolymer chitosan (2-amino-2-deoxy-D-glucose and 2-acetamido-2-deoxy-D-glucose copolymer) [1] . The results indicated that the physical drying process may decisively affect the molar mass of the biopolymer, and the drying of chitosan with supercritical CO 2 (SAS) was reduced more than 10 times its molar mass (from 35.3 to 3.0 kDa).…”

<b>Optimization of lactic fermentation for extraction of chitin from freshwater shrimp waste

“…As freshwater shrimp farming activity has expanded, it has become more important to characterize the waste and develop processes to exploit it as a resource, to prevent environmental problems and obtain high added value products such as chitosan. Following the earlier work of our group on the chemical extraction of chitin and chitosan production (Arantes et al, 2015) the present work proposes the use of a fermentation method for extracting chitin capable of replacing the traditionally used chemical method.…”

“…Chitin is 15-20% of the mass of the residue and can be converted to chitosan through deacetylation, which is the conversion of acetamide groups (-NHCOCH 3 ) to amino (-NH 2 ) groups (Tolaimate, Desbrieresb, Rhazia, & Alaguic, 2003). The development of optimized techniques from the preparation of shells, through chitin extraction to chitosan production aims to obtain chitosan with specific characteristics depending on the type of application, with emphasis on the degree of deacetylation and the molar mass of the biopolymer (Yue, Yao, & Wei, 2009;Arantes et al, 2015).…”