Screening of industrial enzymes for deproteinization of shrimp head for chitin recovery

Food grade proteolytic enzymes were examined for deproteinization of shrimp head. Shrimp head was easily deproteinized by Alcalase ® and trypsin at a pH of 8.0. Alcalase was chosen as the most efficient commercial enzyme for deproteinization of shrimp head. Alcalase treatment of shrimp head recorded 61% of weight loss on dry basis and a residual protein of 275 mg/g dried shrimp head. The enzymatically deproteinized shrimp head was later demineralized with lactic acid using microwave radiation at 400W. The combination of enzymatic and physicochemical treatments promoted the chitin recovery from dried shrimp head under eco-friendly conditions.     

Antioxidant production and chitin recovery from shrimp head fermentation with Streptococcus thermophilus

Fermentation of shrimp head was conducted using Streptococcus thermophilus to produce antioxidant and recover chitin. Fermentation conditions were found to be 10% shrimp head concentration, 5% glucose concentration, 1.2%(v/v) inoculum size, and 64 h of incubation time at 42°C to attain an initial pH of 5.00 with response surface method optimization and the actual deproteinization rate obtained was 93.59%. Antioxidant activity in the supernatant fluid increased greatly during fermentation, the DPPH radical scavenging ability of the culture supernatant was about 98.70%. The concent-ration of astaxanthin, phenolic compounds, and free amino acid in the culture supernatant was 1.774 μg/mL, 589.69 μg gallic acid equivalents/mL, and 796.978mg/mL, respectively. Comparison of the FT-IR spectra and X-ray diffraction (XRD) analysis among commercial chitin (CTa), chitin prepared by the S. thermophilus fermentation (CTb), and chitin prepared by chemical treatments (CTc) demonstrated that CTb had the highest degree of deacetylation.     

南美白对虾甲壳素提取工艺的优化

用柠檬酸和氢氧化钠分别脱除了南美白对虾下脚料中的钙和蛋白质,制备了食品级的甲壳素,同时还综合利用了下脚料中的钙和蛋白质,制备了纯净的柠檬酸钙和蛋白质粉.实验结果表明南美白对虾下脚料中甲壳素的制备方法为:虾壳的力度大小为5 mm,以10%的柠檬酸浸泡10 h,废液用来回收柠檬酸钙;脱钙后的虾壳用10%的氢氧化钠浸泡3 h脱蛋白,废液回收,用盐酸中和至pH5.5制备蛋白粉.     

酶法从虾壳中提取甲壳素工艺优化的研究

利用蛋白酶水解虾壳,以水解率为指标,研究了各种条件对水解效果的影响。通过比较不同蛋白酶的水解效果,发现碱性蛋白酶的水解效果最好,最适的水解条件为:碱性蛋白酶添加量5000U/g,pH8.5,水解温度60℃,水解时间6h,水解pH为8.5,底物质量浓度2g/100mL,在此条件下,水解率达到78.3%。最后通过扫描电镜(SEM)观察了采用不同脱除蛋白方法处理后的甲壳素表面状态,酶法与碱法脱蛋白对甲壳素表面微观状态影响不同,酶法脱蛋白后甲壳素表面较光洁,证实本方法分离效果合理。      

凡纳滨对虾虾头制备甲壳素工艺的研究

采用自溶法对凡纳滨对虾虾头脱除蛋白质后,研究螯合剂脱钙制备甲壳素的工艺条件。以脱钙率为考察指标,依据单因素实验结果,采用Box-Behnken中心组合实验和响应面分析法考察螯合剂EDTA·Na2浓度、反应时间和pH对脱钙率的影响。实验结果表明,EDTA·Na2螯合脱钙最佳工艺条件为:EDTA·Na2浓度9%（m/V）,反应时间2.5h,pH8.0,在此条件下脱钙率为99.56%±0.06%。      

离子液体在虾壳甲壳素提取中的应用研究进展

文章综述了虾壳在离子液体中的溶解与再生、甲壳素提取物的组成及结构表征,分析了离子液体种类、溶解条件对甲壳素提取效果的影响规律,并展望了今后的研究方向。     

超声波辅助提取虾壳甲壳素的工艺研究

通过单因素实验和正交实验,探讨了利用超声波辅助提取虾壳中甲壳素的工艺条件。结果表明:脱除虾壳中无机盐的最佳条件为:室温、超声波频率60kHz、功率180W、柠檬酸浓度为14%、液料比为12∶1(mL/g)、反应时间22min;脱除虾壳中蛋白质的最佳条件为:60℃,超声波频率60kHz,功率100W,NaOH浓度为5%,液料比为5∶1(mL/g),反应时间20min。在最佳提取工艺下制备的甲壳素产品含氮量为5.92%,灰分含量为0.04%,水分含量为3.8%,得率21.3%。     

柠檬酸-反相微胶团法提取虾壳中甲壳素的研究

以虾壳为原料,采用柠檬酸反向微胶团法研究出一种新型的制备甲壳素的方法。首先用食品级的柠檬酸结合超声波辅助萃取技术脱除虾壳中的无机盐,再用微胶团萃取技术脱除虾壳中的蛋白质,再用30%的双氧水脱色,从而制得甲壳素。在单因素实验的基础上,通过响应面设计,得到柠檬酸反相微胶团法提取虾壳中甲壳素的最优条件。并将该法与酸碱法和酶法制备甲壳素产率进行了对比。结果表明,最优条件为:40 m L反相微胶团中虾壳的原料添加量为0.62 g、KCl浓度为0.15 mol/L、萃取时间为116 min,产率为47.32%。柠檬酸反相微胶团法甲壳素产率极显著低于传统的酸碱法,但极显著高于酶法。该方法可行,可为甲壳素生产工艺的改进提供理论基础。      

Plant inhibitors of proteolytic enzymes

The presence of inhibitors of proteinases was stated in many species of plants. There are macropeptides of the molecular weight ranging from 3700 to 8000, often bound to carbohydrates. Potential sources of inhibitors of proteinases are legumes, cereals, potatoes and also some fruits. They are characterized by different activity. "Single-headed" inhibitors inhibit one type of proteolytic enzyme, when "double-headed" inhibitors, possessing two independent active sites, can inhibit several types of proteolytic enzymes at the same time. They also differ in the resistance to temperature and change of pH. The role and importance of inhibitors of proteinases is not exactly explained. They are used in the pharmaceutical, baking and beer-industry as well as in the therapy of numerous diseases.     

The cryoprotectant effect of shrimp chitin and shrimp chitin hydrolysate on denaturation and unfrozen water of lizardfish surimi during frozen storage

Shrimp chitin and shrimp chitin hydrolysate prepared from black tiger (Penaeus monodon), endeavour (Metapenaeus endeavouri) and giant freshwater (Macrobrachium rosenbergii) prawns were added to lizardfish surimi, and it was frozen and stored at −25 °C for 6 months to evaluate freeze-induced protein denaturation. Changes in total Ca-ATPase activity and the amount of unfrozen water in samples were periodically determined during frozen storage. The surimi containing shrimp chitin showed the same freeze-denaturaion rate (K_D) as the surimi without cryoprotectants (control), and the amount of unfrozen water was lower than that of control. However, surimi containing shrimp chitin hydrolysates showed K_D values equal to surimi containing sucrose or glucose but lower than the control, and the amount of unfrozen water was increased compared to control. The results revealed that shrimp chitin hydrolysates retarded the effects on freeze-induced denaturation by stabilizing the hydrated water molecules that surround the protein.     

Characterisation of trypsin purified from the viscera of Tunisian barbel (Barbus callensis) and its application for recovery of carotenoproteins from shrimp wastes

Trypsin was purified from the viscera of barbel by precipitation using ammonium sulphate (0-80%), Sephadex G-100, and Mono Q-Sepharose ion exchange chromatography. The trypsin was purified 27-fold, with 79 U/mg specific activity and 31% recovery. The enzyme had a molecular weight of 24 kDa; purified trypsin appeared as a single band on native-PAGE. The optimum pH and temperature for enzyme activity were pH 10.0 and 55 °C with BAPNA used as a substrate. The N-terminal amino acid sequence of the first 12 amino acids of the purified trypsin was IVGGYECTPYSQ. The Michaelis-Menten constant (K_m) and catalytic constant (k_cat) values of the enzyme were 0.018 mM and 1.21 s⁻¹, respectively. The study also investigated the effects of purified trypsin on the recovery of carotenoproteins from shrimp (Parapenaeus longirostris) shells through hydrolysis using 1.0 U barbel trypsin/g shrimp shells for 1 h at 30 °C. The freeze-dried carotenoproteins recovered contained 71.09% protein, 16.47% lipid, 7.78% ash, and 1.79% chitin.     

Characterisation and partial purification of proteolytic enzymes from sardine by-products to obtain concentrated hydrolysates

A procedure to recover proteases and lipases from the by-products of Monterey sardine (Sardinops sagax caerulea) has been developed, comprising 2 steps: a centrifugation at low temperature to eliminate more than 90% of the initial fat content, and an acetone precipitation step. After this treatment, enzymatic activity increased by 33.8% for lipase, 15.5% for trypsin, 14.8% for chymotrypsin, 93.4% for aminopeptidase, and 19.7% for pepsin. The extents of hydrolysis of fish by-product proteins by endogenous enzyme by-product extract, viscera concentrate extract, and commercial Alcalase® were 62%, 85%, and 28%, respectively. The two extract preparations from sardine by-product (viscera and by-product concentrate extracts) produced 3-fold greater hydrolysis than with the commercial enzyme. The recovery of enzyme concentrates from sardine waste has both ecological and economical advantages for the fish industry.     

喷雾干燥应用于对虾加工废弃物制造水解蛋白粉的研究

以南美白对虾加工废弃物(虾头,虾壳)为原料,通过蛋白酶酶解处理后采用喷雾干燥工艺制造水解蛋白粉,重点研究进风温度、入料浓度、助干剂添加量(虾固形物与麦芽糊精比例)对水解蛋白粉品质的影响。结果表明,当喷雾干燥的进风温度为190℃、入料浓度为15%、虾固形物与麦芽糊精比例为4:1时,所得到的水解蛋白粉品质最好,表现出水分含量低、色泽好、虾香味浓郁,其氨基酸态氮含量为3·988%,水分含量为2·90%。      

Antibacterial activity of chitin,chitosan and its oligomers prepared from shrimp shell waste

The antimicrobial activities of chito-oligosaccharides against four Gram-positive and seven Gram-negative bacteria were compared to chitosan and chitin with an emphasis on the effects of biopolymer molecular weight (Mv) and degree of deacetylation (DD). Chitin was isolated from shrimp (Parapenaeus longirostris) shell waste by sequential chemical treatments. Chitosan and its oligomers N-acetyl chito-oligosaccharides and chito-oligosaccharides were prepared by deacetylation and chemical hydrolysis, respectively. Chitin exhibited a bacteriostatic effect on Gram-negative bacteria, Escherichia coli ATCC 25922, Vibrio cholerae, Shigella dysenteriae, and Bacteroides fragilis. Chitosan exhibited a bacteriostatic effect on all bacteria tested, except Salmonella typhimurium. The oligomers exhibited a bactericidal effect on all bacteria tested.     

Recent development of anaerobic digestion processes for energy recovery from wastes

Anaerobic digestion leads to the overall gasification of organic wastewaters and wastes, and produces methane and carbon dioxide; this gasification contributes to reducing organic matter and recovering energy from organic carbons. Here, we propose three new processes and demonstrate the effectiveness of each process. By using complete anaerobic organic matter removal process (CARP), in which diluted wastewaters such as sewage and effluent from a methane fermentation digester were treated under anaerobic condition for post-treatment, the chemical oxygen demand (COD) in wastewater was decreased to less than 20 ppm. The dry ammonia-methane two-stage fermentation process (Am-Met process) is useful for the anaerobic treatment of nitrogen-rich wastes such as waste excess sludge, cow feces, chicken feces, and food waste without the dilution of the ammonia produced by water or carbon-rich wastes. The hydrogen-methane two-stage fermentation (Hy-Met process), in which the hydrogen produced in the first stage is used for a fuel cell system to generate electricity and the methane produced in the second stage is used to generate heat energy to heat the two reactors and satisfy heat requirements, is useful for the treatment of sugar-rich wastewaters, bread wastes, and biodiesel wastewaters.     

One-step bio-extraction of chitin from shrimp shells by successive co-fermentation using Bacillus subtilis and Lactobacillus plantarum

Chitin was bio-extracted in one-step from shrimp shells by successive co-fermentation using Bacillus subtilis and Lactobacillus plantarum in this study. To construct this co-fermentation system, B. subtilis was first cultured for 3 days for deproteinization (DP), and then L. plantarum was inoculated for demineralization (DM). After 6 days of co-fermentation, the final DP and DM efficiency reached 94.1% and 96.3%, respectively. The molecular weight, degree of acetylation, and crystalline index of chitin were reduced by 9.8, 5.6 and 1.4% with the DP time of 2 days extending to 3 days. Meanwhile, L. plantarum instead of B. subtilis became the dominant bacterium on day 5 of co-fermentation, with L. plantarum count of 6.19 log CFU/mL and lactic acid concentration of 28.22 g/L, respectively. The chitin prepared in this study exhibited similar structural characterization as commercial chitin. One step successive co-fermentation was a simple and feasible approach for high-quality chitin preparation.Industrial relevance: This study establishes one-step bio-extraction of chitin from shrimp shells by successive co-fermentation using B. subtilis followed by L. plantarum. One-step successive co-fermentation simplifies the intermediate processes of conventional two-step fermentation for extracting chitin. DP and DM happen during the entire co-fermentation period, which helps to achieve satisfactory DP and DM efficiency. This innovative yet simple method provides more possibilities for the biotechnological production of chitin on an industrial scale.