Institute of Biology for Engineers and Biotechnology of Wastewater, Karlsruhe Institute of Technology, Am Fasanengarten, Karlsruhe 76131, Germany.
Microb Cell Fact. 2013 Oct 5;12:90. doi: 10.1186/1475-2859-12-90.
After cellulose and starch, chitin is the third-most abundant biopolymer on earth. Chitin or its deacetylated derivative chitosan is a valuable product with a number of applications. It is one of the main components of shrimp shells, a waste product of the fish industry. To obtain chitin from Penaeus monodon, wet and dried shrimp shells were deproteinated with two specifically enriched proteolytic cultures M1 and M2 and decalcified by in-situ lactic acid forming microorganisms. The viscosity of biologically processed chitin was compared with chemically processed chitin. The former was further investigated for purity, structure and elemental composition by several microscopic techniques and (13)C solid state NMR spectroscopy.
About 95% of the protein of wet shrimp shells was removed by proteolytic enrichment culture M2 in 68 h. Subsequent decalcification by lactic acid bacteria (LAB) took 48 h. Deproteination of the same amount of dried shrimps that contained a 3 × higher solid content by the same culture was a little bit faster and was finished after 140 h. The viscosity of chitin was in the order of chemically processed chitin > bioprocessed chitin > commercially available chitin. Results revealed changes in fine structure and chemical composition of the epi-, exo- and endocuticle of chitin from shrimp shells during microbial deproteination and demineralization. From transmission electron microscopy (TEM) overlays and electron energy loss spectroscopy (EELS) analysis, it was found that most protein was present in the exocuticle, whereas most chitin was present in the endocuticle. The calcium content was higher in the endocuticle than in the exocuticle.13C solid state NMR spectra of different chitin confirmed < 3% impurities in the final product.
Bioprocessing of shrimp shell waste resulted in a chitin with high purity. Its viscosity was higher than that of commercially available chitin but lower than that of chemically prepared chitin in our lab. Nevertheless, the biologically processed chitin is a promising alternative for less viscous commercially available chitin. Highly viscous chitin could be generated by our chemical method. Comprehensive structural analyses revealed the distribution of the protein and Ca matrix within the shrimp shell cuticle which might be helpful in developing shrimp waste processing techniques.
在纤维素和淀粉之后，甲壳素是地球上第三丰富的生物聚合物。甲壳素或其脱乙酰衍生物壳聚糖是一种具有多种应用价值的宝贵产品。它是虾壳的主要成分之一，是鱼类工业的一种废物。为了从斑节对虾中获得甲壳素，用两种特别富集的蛋白酶 M1 和 M2 将湿虾壳和干虾壳进行脱蛋白处理，并通过原位形成的乳酸菌进行脱钙处理。生物处理的甲壳素的粘度与化学处理的甲壳素进行了比较。通过几种微观技术和（13）C 固态 NMR 光谱法对前者进行了进一步的纯度、结构和元素组成的研究。
用蛋白酶富集培养物 M2 在 68 小时内去除了湿虾壳中约 95%的蛋白质。随后用乳酸菌（LAB）脱钙需要 48 小时。用相同的培养物对含有 3 倍高固体含量的相同量的干虾进行脱蛋白处理稍微快一点，140 小时后完成。甲壳素的粘度顺序为化学处理的甲壳素>生物处理的甲壳素>市售的甲壳素。结果表明，在微生物脱蛋白和脱矿过程中，虾壳的外、中、内表皮的精细结构和化学组成发生了变化。从透射电子显微镜（TEM）叠加和电子能量损失光谱（EELS）分析中发现，大多数蛋白质存在于外表皮中，而大多数甲壳素存在于内表皮中。内表皮中的钙含量高于外表皮。不同甲壳素的 13C 固态 NMR 光谱证实最终产物中的杂质含量<3%。
虾壳废物的生物处理得到了高纯度的甲壳素。它的粘度高于市售的甲壳素，但低于我们实验室中化学制备的甲壳素。然而，生物处理的甲壳素是一种有前途的替代粘性较低的市售甲壳素的选择。高粘性的甲壳素可以通过我们的化学方法生成。综合结构分析揭示了蛋白质和 Ca 基质在虾壳表皮内的分布，这可能有助于开发虾壳废物处理技术。
