Methods of Chitin Production a Short Review

Such characteristics, diverse applications in areas such as agriculture, food, environmental, and as two areas with greater focus: pharmaceutical and health [3,4]. Its structure consists of N-acetyl-d-glucosamine units with β- (1,4) bonds, having as main characteristic the insolubility in water and some organic acids [5]. Chitin belongs to the group of structural polysaccharides, together with cellulose, the second polymer being more abundant in the biosphere [6-9]. Due to its structural nature, a product release system was not found in any of the arthropod exoskeleton, in the structures of molluscs [10], in the cell wall of fungi [11,12], protozoa and bacteria, egg shells of nematodes [13,14], the shrimp fishery residue being the most widely used source [15].Throughout the decades of research and handling of this polymer, many methods of extraction have been developed, being the chemical method most found in the literature, being also used in the means of production of industrial chitin. The USA, Japan, India, Canada, China, South Korea, Russia and Norway generally use the reject of crustacean fishing for production. The use of strong acids and bases in the chitin extraction process generates critical points to the process, such as: high cost of the materials involved, generation of chemical effluent and final product with low levels of purity [16,17]. Biological processes become more attractive because they have an affordable cost of production, do not generate high risk effluent (such as the chemical process) and high-quality final product [18,19]. All the processes found in the literature are an objective: to obtain chitin by separating the proteins and minerals from the raw material used [20]. Chitin, besides having great biotechnological value, generates by-products (such as chitosan) that also have added value and even more relevant properties. In this paper we discuss the already known processes of obtaining chitin known and registered in the literature of 2010 up to the present moment: Chemical, enzymatic and biological processes relating the different methods of obtaining and with the objective to identify the particularities of each process regarding the industrial viability and economically balancing them so that the reader concludes the best process for their research, also the possibility of executing quality improvements in these processes. We will also discuss the polymorphic structures of α- and β-chitin and the different methods of obtaining each, since different processes are required in each of them due to their structures, properties and reactivity. The main objective of this review is to be able to relate the different processes of obtaining chitin with the most suitable applications for the method, based on such relation in aspects such as degree of purity and economic applicability.

该类物质具备多样应用场景，覆盖农业、食品、环境等领域，其中医药与健康两大领域为重点关注方向[3,4]。其结构由带有β-(1,4)糖苷键的N-乙酰-D-葡糖胺（N-acetyl-d-glucosamine）单元构成，核心特征为不溶于水及部分有机酸[5]。甲壳素（Chitin）属于结构多糖类，与纤维素（cellulose）同属此类，是生物圈中含量第二丰富的聚合物[6-9]。基于其结构特性，在节肢动物外骨骼、软体动物组织[10]、真菌细胞壁[11,12]、原生动物与细菌，以及线虫卵壳[13,14]中均未发现专属的产物释放系统，而虾类渔业副产物是目前应用最广泛的甲壳素来源[15]。历经数十年对该聚合物的研究与应用开发，现已衍生出多种提取方法，其中化学法在文献中最为常见，同时也是工业化生产甲壳素的主流手段。美国、日本、印度、加拿大、中国、韩国、俄罗斯及挪威等国通常以甲壳类捕捞副产物作为生产原料。在甲壳素提取过程中使用强酸与强碱会带来诸多工艺痛点，例如：原料成本高昂、产生化学废液，以及最终产物纯度较低[16,17]。生物法则更具优势，其生产成本可控，不会产生类似化学法的高风险废液，且可得到高品质的最终产物[18,19]。现有文献记载的所有提取工艺，核心目标均为从原料中分离蛋白质与矿物质，从而获取甲壳素[20]。甲壳素不仅具备极高的生物技术价值，其衍生副产物（如壳聚糖（chitosan））同样具备附加值，且拥有更为优异的相关特性。本文将梳理2010年至今文献中记载的所有已知甲壳素提取工艺，包括化学法、酶解法与生物法，对比各类提取方法的差异，旨在阐明各工艺在工业可行性与经济性层面的独特性，帮助读者结合自身研究需求选出最优方案，同时探讨上述工艺的质量提升路径。此外，本文还将探讨α-甲壳素与β-甲壳素的多晶型结构，以及各自对应的专属提取方法——由于二者在结构、性质与反应活性上存在差异，因此需采用不同的工艺进行制备。本综述的核心目标，是基于产物纯度与经济适用性等维度，将不同的甲壳素提取工艺与其最适配的应用场景进行关联匹配。