Summary The chitosan biopolymer can be used as a proton‐conducting membrane in proton‐exchange membrane fuel cell. In the forms that they have normally obtained and tested, chitosan membranes typically show poor performance in conduction of protons, requiring modifications in the structure of the biopolymer or blending with other polymers to increase its proton conductivity. The present work investigates the individual properties of chitosan and relates them to the proton conductivity performance of membranes composed of this polymer. Evaluation was made of the effects of variables such as the degree of deacetylation (DD) and the molar mass (Mv) of chitosan membranes without addition of any other polymer. The DD and Mv values of the chitosan used to produce membranes determined the proton conduction, with lower DD and higher Mv resulting in higher conductivity. The thicker membranes presented greater crystallinity, with conductivity between 2.0 × 10−4 and 1.8 × 10−3 S cm−1. The characteristic stages of degradation of the chitosan membranes were in the ranges 200 to 300°C and 500 to 600°C, indicating good thermal stability of the material.

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ABSTRACT. Freshwater shrimp shells from the shrimp farming activity in tanks, were processed for biological extraction of chitin, by fermentation with Lactobacillus plantarum isolated from meat products, offering an advantageous demineralization and deproteination of the residue, replacing the chemically. Deproteination was obtained approximately 99% and demineralization of up to 87% using batch fermentations with a maximum of 72 hours and the use of simple strategies such as pH adjustment and reinoculation. The performance of chitin was about 40% greater than in the chemical extraction and the results indicate an interesting method in the process of production of chitosan, where the biopolymer chitin is precursor.Keywords: shrimp shells, chitosan, Lactobacillus plantarum, bioprocess.Otimização de fermentação lática para extração de quitina de resíduos de camarão de água doce RESUMO. Carapaças de camarão de água doce provenientes da atividade de carcinicultura em tanques foram processadas para extração biológica de quitina, por meio da fermentação com Lactobacillus plantarum isolado de produtos cárneos, oferecendo uma via vantajosa de desmineralização e de desproteinização do resíduo, em substituição à via química. Obteve-se desproteinização de cerca de 99% e desmineralização de até 87% por intermédio de fermentações em batelada com duração máxima de 72 horas e o uso de estratégias simples, como ajuste de pH e reinoculação. O rendimento de quitina foi cerca de 40% maior do que na extração química, e o conjunto dos resultados indica um método interessante no processo de produção de quitosana, em que o biopolímero quitina é precursor.Palavras-chave: carapaças de camarão, quitosana, Lactobacillus plantarum, bioprocesso.

Membranes prepared with commercial chitosan and with chitosan extracted from carapaces of freshwater shrimp were developed to be tested as low cost electrolyte in PEM-FC fuel cells. The main factors of interest of this research are related to the possibility that the biopolymer might undergo physical and chemical modifications due to amine groups (-NH 2) existing in the structure. The shrimp carapaces were obtained from residues of shrimp farming in the West Region of Paraná-Brazil. Researches testing chitosan membranes as proton conductors usually apply matrices of other polymers together, forming composites with more suitable properties for this purpose. Very few studies investigate the effects of chitosan properties for obtaining these membranes and normally, membranes of commercial chitosan are utilized. In original research, it was investigated the influence of the degree of deacetylation (DDA) and the molar mass (Mv) of chitosan used in the preparation of membranes on the performance regarding proton conductivity and other properties. For obtaining chitosan and membranes, classical chemical methods were applied. The results indicate that chitosan produced in laboratory led to obtaining membranes with promising properties, presenting proton conductivity one hundred times higher when compared to those presented by commercial chitosan membranes, which are in order of 1,6 and 1,9 10-2 S.cm-¹. The significant increase in proton conductivity can be associated with the higher number and availability of-NH 2 groups existent in chitosan with higher DDA and lower Mv, produced in laboratory. The versatility of chitosan and the possibility