Ind. Eng. Chem. Res. 2001, 40, 5885-5888
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Production of Valuable Materials by Hydrothermal Treatment of Shrimp Shells Armando T. Quitain,† Nobuaki Sato, Hiroyuki Daimon,* and Koichi Fujie Department of Ecological Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi 441-8580, Japan
The possibility of amino acids and glucosamine production from the treatment of shrimp shells in high-temperature and high-pressure water was investigated. Under the tested conditions, the highest amount of amino acids (70 mg/g of dry shrimp shell) from hydrolysis of proteins was obtained at a reaction temperature of 523 K in 60 min. This amount was about 2.5 times the total amino acids obtained at 363 K, the temperature at which shrimp extracts for use in noodles soup are being prepared. The amount of simple amino acids such as glycine and alanine increased with increasing temperature up to 523 K and decreased thereafter. This behavior has also been observed from other seafood processing wastes such as fish entrails and scallop wastes. Glucosamine was not detected presumably because of its deamination to produce glucose or cellulose. To further investigate the reason for the nonformation of glucosamine from shrimp shells, experiments on chitin as the starting reaction material were carried out. Introduction Industrial processes always accompany wastes that pose significant risk to the environment. Technologies that would treat these wastes, or even better recover some useful organic materials before disposal, are necessary to mitigate pollution. In a local seafood processing company in Japan, 7-10 tons of shrimp are processed daily. About 30% of this amount, containing mostly shells, is discarded as wastes. Shrimp shells normally contain about 17% chitin and 42% proteins;1 recovery of these useful products or their derivatives is significant from an industrial and ecological viewpoint. Chitin [β-1,4-poly(n-acetyl-D-glucosamine)] can be converted to glucosamine by deacetylation and hydrolysis,2 while proteins can be hydrolyzed to form amino acids.3 Glucosamine, as medicine, can help rebuild damaged joints, tendons, cartilage, and soft tissue. It is also believed to cure osteoarthritis, the most common form of arthritis that affects cartilage.4,5 In a local company, glucosamine in combination with chloride or acetate is utilized to manufacture commercial products such as “natural glucosamine” and “NA-COS-Y”, respectively. These products are considered to have various possible applications in the food industry;6 however, additives are necessary to offset the unpleasant taste of glucosamine. Amino acids, on the other hand, have wide uses in pharmaceuticals, food products, animal nutrition, and cosmetic industries. As medicine, they are used in treating various diseases such as renal, gastrointestinal, endocrinal, and dermal diseases among others. In the food industry, amino acids can be used as taste enhancers [e.g., sweetness, glycine (Gly) and alanine (Ala); sourness, glutamine (Glu) and asparagine (Asp); bitterness, arginine (Arg)] and as animal feeds. If each amino acids could be separated individually, these could * Corresponding author. E-mail:
[email protected]. Tel: +81-532-44-6910. Fax: +81-532-44-6910. † Current address: Research Institute for Solvothermal Technology, 2217-43 Hayashi, Takamatsu, Kagawa 761-0301, Japan.
also be reagents for the synthesis of new materials including electronic-related chemicals (e.g., for liquid crystals and exposure liquids for color copiers).7 High-temperature and high-pressure (HTHP) water technology can be applied to recover glucosamine and amino acids from these wastes. Reactions in HTHP water have been gaining interest recently because of the fascinating properties of water as a reaction medium at elevated temperatures and pressures.8,9 At room temperature and atmospheric pressure, water has a dielectric constant of 80 and an ion product (KW) of 10-14. These values can be controlled by manipulating temperature and pressure and could greatly affect the reactivity of various compounds in water. The dielectric constant expresses the affinity of water as a solvent to reaction substances especially for nonpolar materials. In addition, an ion product of water can also be adjusted to control the ability of hydrolysis, favoring hydrolysis at high ion product. Under saturated vapor pressure, water has a maximum ion product at around 250 °C. Numerous studies have been carried out on the application of HTHP water, and the technique was found to be useful especially on wastewater treatment10 and solid waste resource recovery.11 Some recent works deal with the application of the technology to recover useful materials from various organic wastes, including plastic,12,13 cellulosic,14 and proteinaceous wastes.3,15,16 In the area of resource recovery from seafood processing wastes, Yoshida et al.15 applied hydrolysis in subcritical water to produce organic and amino acids from fish meat. They observed that liquefaction of fish meat occurs rapidly using subcritical water, the optimum conditions for the production of amino acids such as cystine, glycine, etc., were reported at 543 K (5.51 MPa). Production of other useful organic acids such as lactic acid, pyroglutamic acids, etc., was also observed. In our previous work, production of amino acids from waste fish entrails by hydrolysis in sub- and supercritical water was optimized by varying the temperature and reaction time using batch and semibatch reactors.3,16 Ren and his co-researchers tried to make extracts for commercial soup bases by hot water treatment of crab
10.1021/ie010439f CCC: $20.00 © 2001 American Chemical Society Published on Web 11/10/2001
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Figure 1. Schematic diagram of the batch reactor apparatus.
and shrimp shells.17 Results showed that the best extractability was obtained in 3 h at 373 K. In addition, Watanabe and Mohri carried out experiments on chitin at around 573-623 K at a constant pressure of 30 MPa to investigate the possibility of hydrothermal extraction of nutritional materials from crab shells.18 The reaction time was in the range of 60-1800 s. It was observed that a maximum of about 50% of chitin could be decomposed under the tested conditions. This research investigates the possibility of producing amino acids and glucosamine from shrimp shells by reaction in HTHP water under sub- and supercritical conditions. Experimental Apparatus and Methodology Properties of Shrimp Shells. Shrimp shells were obtained from a local seafood company. The shells were reduced in size by using a mixing cutter (CQM-N1, Toshiba Corp.) and then stored in a freezer at 252 K. The water content was about 80 wt %. The shells were found to contain about 30 wt % (300 mg/g of dry shell) amino acids by hydrolysis using 6 N HCl acid in 22 h. This value corresponds to the amount of proteins originally present in the sample. The obtained amino acids were mainly glutamine, aspartic acid, and histidine. Batch Reactor Apparatus. The schematic diagram of a batch reactor apparatus is shown in Figure 1. The apparatus (TSC-006, Taiatsu Glass Corp.) consists of a stirrer, a pressure gauge, the reactor, and a molten salt bath containing mixtures of potassium nitrate and sodium nitrate. The reactor made up of Hastelloy C22 (an alloy of Ni, Cr, Mo, and others) has a total inside volume of 66 cm3. This can be operated at a maximum temperature of 873 K and a maximum pressure of 45 MPa. Experimental Methodology. In each run, about 2 g sample of shrimp shells (0.4 g, dry basis) and 50 mL of deionized water (weight ratio ) 1:125, dry basis) were placed into the reactor. The reactor was sealed, and then the air inside was purged using a vacuum pump. The reactor was immersed into the preheated molten salt bath to start the reaction. After the desired reaction time had elapsed, the reactor was plunged into a water bath to bring them quickly to room temperature, effectively ceasing any occurring reactions. It is most likely that quenching had an affect on the reaction products, but this was not considered in this present study. The experiments were conducted at various temperatures (363, 473, 523, 573, and 673 K) and reaction times (5-60 min).
Figure 2. Yield of total amino acids at various reaction temperatures and times.
Analytical Methods. The amino acids of the reaction products were determined using an amino acid analyzer (LC-10AD, Shimadzu Corp.). The amino acid analyzer is a combination of an ion-exclusion column (Shim-pack Amino-Na, Shimadzu Corp.) and postcolumn labeling methods with a spectrofluorophotometer (RF-10A, Shimadzu Corp.). In sample preparation for amino acid analysis, filtration was done using an ultrafiltration membrane (30 000 fractional molecular weight, Millipore Ultra Free C3) to maintain a good performance of the chromatographic system. The quantities of 17 kinds of amino acids (presented here according to elution order)saspartic acid (Asp), threonine (Thr), serine (Ser), glutamine (Glu), proline (Pro), glycine (Gly), alanine (Ala), cystine (Cys), valine (Val), methionine (Met), isoleucine (ILeu), leucine (Leu), tyrosine (Tyr), phenylalanine (Phe), histidine (His), lysine (Lys), and arginine (Arg)swere determined in each analytical run. Glucosamine and ammonia were also analyzed using the amino acid analyzer. The amount of acetic acid was measured using an organic acid analyzer (LC-10A, Shimadzu Corp.). The organic acid analysis system consists of an ion-exclusion column (Shim-Pack SCR-102H) and an electroconductivity detector. The compounds that can be analyzed are aliphatic carboxylic acids, hydroxycarboxylic acids, ketocarboxylic acids, and other organic acids having a dissociation constant (pKa) of 2-5 and a carbon number of 5 or less. Results and Discussion Several experiments were carried out under hydrothermal conditions to study the possibility of amino acids and glucosamine production from shrimp shells. The results are discussed in subsequent sections. Amino Acid Production. Figure 2 shows the yield of amino acids at various reaction temperatures and times. These amino acids were produced from hydrolysis of proteins originally present in shrimp shell samples. The amount at zero reaction time corresponds to the amino acids that are soluble in water at room temperature. This was determined by soaking the sample in water for 30 min. The reaction was first conducted at 363 K, the temperature at which soup bases for use in noodles are prepared from crab or shrimp shells in a local food company. At this temperature, only about 25 mg/g of dry shell was obtained. This low yield is presumably due to the low ion product of water at this temperature. It should be noted that high ion product
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Figure 4. Speculated reaction pathway of the hydrothermal decomposition of chitin.
Figure 3. Effect of the reaction temperature on the yield and composition of amino acids.
of water favors the hydrolysis reaction, as has been previously mentioned. It is most likely that only extraction of soluble amino acids took place. At 523 K, about 25% of the original amino acids in the sample (as determined by acid hydrolysis) were recovered at a reaction time of 30 min. This corresponds to about 2.5 times the amount obtained at 363 K at the same reaction time. At temperatures higher than 523 K, the amino acids decompose fast, resulting in a low yield as time progresses. At 573 K and a reaction time of 30 min, almost all amino acids decomposed to organic acids and ammonia by decarboxylation and deamination, respectively. At a reaction time of 60 min, the specific yield of each amino acid at various temperatures is shown in Figure 3. It was observed that as the temperature increases the amount of Gly and Ala also increases. The same results were observed in the case of other seafood processing wastes such as fish entrails and scallop waste.16,17 This is due to the stability of simple amino acids in HTHP water. It is also possible that complex amino acids decompose to form simple amino acids (i.e., Gly and Ala). Considering that these compounds are intended for use in food additives and taste enhancers, the results suggest that proper control of treatment conditions (i.e., temperature and time) is necessary to obtain the desired taste. Sourness is enhanced by formation of Glu and Asp at low temperature and in a short reaction time. On the other hand, at high temperature and in a long reaction time, production of lowmolecular-weight amino acids such as Gly and Ala can improve sweetness. The overall yield of amino acids using HTHP water is relatively low compared to that in acid hydrolysis. Although the use of acid for the hydrolysis reaction is a well-established technique, to our knowledge, this method has not been considered commercially for the treatment of shrimp shells. This is presumably due to the difficulty in removing the acids from the products in addition to the long treatment time the process would require. Our goal for carrying out this research is to develop a process that would be able to treat an enormous amount of shrimp shell wastes, while recovering useful products, using an environmentally benign and health-risk-free solvent. Glucosamine Production. Another interesting product that can be derived from hydrothermal treatment of shrimp shells is glucosamine. This can be produced by deacetylation of chitin to chitosan followed by hydrolysis as shown in Figure 4. However, glucosamine was not detected from the reaction products of the
Figure 5. Concentration of the reaction products from decomposition of chitin at various reaction temperatures and times (b, chitin + residues; 4, acetic acid; 0, ammonia).
treatment of shrimp shells under the tested reaction conditions. To further investigate the reason for the nonformation of glucosamine from shrimp shells, experiments on chitin (Nacali Tesque), the source of glucosamine in shrimp shells, were carried out. Experiments were performed at various reaction conditions: 523, 573, 623 K (at its corresponding saturated vapor pressure), and 673 K (45 MPa). To analyze the hydrothermal decomposition of chitin, the behavior of the formation of acetic acids and ammonia was investigated. Acetic acids and ammonia are byproducts of deacetylation and deamination, respectively. Figure 5 summarizes the results of the concentration of reaction products from the decomposition of chitin at various reaction temperatures and times. While chitin and other residues decrease, both ammonia and acetic acid increase with increasing reaction temperatures and times. Glucosamine was not detected under any tested conditions. At temperatures of 523 and 673 K, deacetylation and deamination occurred at the same time as observed from the equimolar production of acetic acid and ammonia. These would result in the nonformation of glucosamine. The presence of glucosamine is expected at 573 and 623 K because of the differences in the amount of acetic acid and ammonia, but still glucosamine was not detected. This can be explained by the fact that, although chitosan may be produced by deacetylation under the tested conditions, deamination of chitosan is favored over hydrolysis, resulting in the nonformation of the desired glucosamine. On the basis of these results and the reaction pathway in Figure 4, the absence of glucosamine in reaction products is presumably due to deamination of chitosan to produce glucose or cellulose. Proper control of the hydrolysis reaction and deamination to form glucosamine by using some additives still needs further investigation.
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Conclusion Hydrothermal decomposition of proteins and chitin in shrimp shells to produce amino acids and glucosamine, respectively, was investigated in this study. About 70 mg of amino acids/g of dry shrimp shell could be obtained at a temperature of 523 K in 60 min. This maximum amount obtained under the tested conditions is about 2.5 times the total amino acids obtained at 363 K. The production of simple amino acids such as Gly and Ala increased with increasing temperature but decreased for temperatures above 523 K. Under all of the reaction conditions investigated in this study, glucosamine was not detected because of its deamination as observed from the increasing amount of ammonia. The control of deamination and hydrolysis of chitin toward the formation of glucosamine using some additives merits further investigation. Acknowledgment This research was funded in part by Japan Society for the Promotion of Science, Research for the Future Program Grant 97I00504 (Causes and Effects of Environmental Loading and Its Reduction). Literature Cited (1) Shahidi, F. Extraction of Value-Added Components from Shellfish Processing Discards. In Food Flavors: Generation, Analysis and Process Influence; Charalambous, G., Ed.; Elsevier Science B.V.: Amsterdam, The Netherlands, 1995. (2) Sakai, K. Function and Application of Chitin-Chitosan Oligomers. New Food Ind. 1998, 40, 17 (in Japanese). (3) Kang, K.; Quitain, A. T.; Daimon, H.; Noda, R.; Goto, N.; Hu, H.; Fujie, K. Optimization of Amino Acids Production from Waste Fish Entrails by Hydrolysis in Sub- and Supercritical Water. Can. J. Chem. Eng. 2001, 79, 65. (4) Sakamoto, K. Glucosamine for Osteoarthritis and Applied for Foods. Bio Ind. 1998, 15, 46 (in Japanese). (5) Glucosamine Sulfate, Using Glucosamine for Wellness. http://glucosamine.net.
(6) Matahira, Y. Function of Glucosamine and Application to Food Products. New Food Ind. 1998, 40, 8 (in Japanese). (7) Amino Acid Related OperationssIndustrial Use. http:// www.ajinomoto.co.jp/ajonomot/A-Life/e-aminoscience. (8) Shaw, R. W.; Brill, T. B.; Clifford, A. A.; Eckert, C. A.; Franck, E. U. Supercritical Water: A Medium for Chemistry. Chem. Eng. News 1991, 12, 26. (9) Savage, P. E.; Gopalan, S.; Mizan, T. I.; Martino, C. J.; Brock, E. E. Reactions at Supercritical Conditions: Applications and Fundamentals. AIChE J. 1995, 41, 1723. (10) Goto, M.; Nada, T.; Kodama, A.; Hirose, T. Kinetic Analysis for Destruction of Municipal Sewage Sludge and Alcohol Distillery Wastewater by Supercritical Water Oxidation. Ind. Eng. Chem. Res. 1999, 38, 1863. (11) Shanableh, A. Production of Useful Organic Matter from Sludge Using Hydrothermal Treatment. Water Res. 2000, 34, 945. (12) Sato, N.; Saeki, T.; Daimon, H.; Fujie, K. Decomposition Reaction of Polyvinyl Alcohol in High-Temperature and HighPressure Water. Kagaku Kogaku Ronbunshu 2001, in press. (13) Adschiri, T.; Sato, O.; Machida, K.; Saito, N.; Arai, K. Recovery of Terephthalic Acid by Decomposition of PET in Supercritical Water (in Japanese). Kagaku Kogaku Ronbunsho 1997, 23, 505 (in Japanese). (14) Sasaki, M.; Kabyemela, B.; Malaluan, R.; Hirose, S.; Takeda, N.; Adschiri, T.; Arai, K. Cellulose Hydrolysis in Subcritical and Supercritical Water. J. Supercrit. Fluids 1998, 13, 261. (15) Yoshida, H.; Terashima, M.; Takahashi, Y. Production of Organic Acids and Amino Acids from Fish Meat by Subcritical Water Hydrolysis. Biotechnol. Prog. 1999, 15, 1090. (16) Daimon, H.; Kang, K.; Sato, N.; Fujie, K. Development of Material Recycling Technology for Marine Wastes. J. Chem. Eng. Jpn. 2001, in press. (17) Ren, H.; Liu, D.; Wang, Y.; Endo, H.; Watanabe, E.; Hayashi, T. Preparation of Hot-Water Extract from Fisheries Waste. Nippon Suisan Gakkaishi 1997, 63, 985 (in Japanese). (18) Watanabe, Y.; Mohri, S. Development of Applying Hydrothermal Reaction for Biomass. Rep. Miyagi Prefect. Inst. Technol. 1998, 29, 110.
Received for review May 14, 2001 Revised manuscript received September 12, 2001 Accepted September 14, 2001 IE010439F
