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Transformation of the matrix structure of shrimp shells during bacterial deproteination and demineralization.

Xu Y, Bajaj M, Schneider R, Grage SL, Ulrich AS, Winter J, Gallert C - Microb. Cell Fact. (2013)

Bottom Line: The viscosity of biologically processed chitin was compared with chemically processed chitin.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.Bioprocessing of shrimp shell waste resulted in a chitin with high purity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biology for Engineers and Biotechnology of Wastewater, Karlsruhe Institute of Technology, Am Fasanengarten, Karlsruhe 76131, Germany. mini.bajaj@kit.edu.

ABSTRACT

Background: 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.

Results: 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.

Conclusions: 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.

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Deproteination of a) wet shrimp shells and b) dried shrimp shells by enrichment cultures M1 and M2. Decalcification with lactic acid, produced in-situ by lactic acid bacteria (LAB) from glucose was started after 68 h in the wet shrimp assay (a) and after 140 h in the dried shrimp assay (b) by addition of glucose and LAB. Twice the amount of glucose had to be added in the dry shrimp shell assay as compared to the assay with wet shrimp shells, due to the higher amount of total solids in dry shrimp shells.
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Figure 1: Deproteination of a) wet shrimp shells and b) dried shrimp shells by enrichment cultures M1 and M2. Decalcification with lactic acid, produced in-situ by lactic acid bacteria (LAB) from glucose was started after 68 h in the wet shrimp assay (a) and after 140 h in the dried shrimp assay (b) by addition of glucose and LAB. Twice the amount of glucose had to be added in the dry shrimp shell assay as compared to the assay with wet shrimp shells, due to the higher amount of total solids in dry shrimp shells.

Mentions: To elucidate whether there exist relevant differences for deproteination of wet or dried P. monodon shells, protein and calcium elimination from the respective abdomen fractions with the proteolytic enrichment cultures M1 and M2 were compared (Figure 1a and b). TKN and protein content of waste shells were determined before each assay. The average TKN and protein content of the shells were 73 mg/g wet weight and 300 mg/g dry weight, respectively as described previously [2]. As shown in Figure 1a, 95% of the protein of 15 g wet weight of shrimp shells (=5.1 g dry weight) was eliminated after 68 h of incubation with enrichment culture M2 and more than 80% was removed with enrichment culture M1. About 80% of the dissolved protein was deaminated during deproteination of wet and dried shrimp shells by both enrichment cultures (Table 1). Although protein removal from dried shrimp shells (Figure 1b) required 120 h (culture M2) or 140 h (culture M1), yet the protein removal rates were much higher than with wet shrimp shells if the dry matter content is taken in consideration. The dry matter amount was 14.1 g and 5.1 g per assay of dried and wet shrimp shells, respectively (Table 2).


Transformation of the matrix structure of shrimp shells during bacterial deproteination and demineralization.

Xu Y, Bajaj M, Schneider R, Grage SL, Ulrich AS, Winter J, Gallert C - Microb. Cell Fact. (2013)

Deproteination of a) wet shrimp shells and b) dried shrimp shells by enrichment cultures M1 and M2. Decalcification with lactic acid, produced in-situ by lactic acid bacteria (LAB) from glucose was started after 68 h in the wet shrimp assay (a) and after 140 h in the dried shrimp assay (b) by addition of glucose and LAB. Twice the amount of glucose had to be added in the dry shrimp shell assay as compared to the assay with wet shrimp shells, due to the higher amount of total solids in dry shrimp shells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3852495&req=5

Figure 1: Deproteination of a) wet shrimp shells and b) dried shrimp shells by enrichment cultures M1 and M2. Decalcification with lactic acid, produced in-situ by lactic acid bacteria (LAB) from glucose was started after 68 h in the wet shrimp assay (a) and after 140 h in the dried shrimp assay (b) by addition of glucose and LAB. Twice the amount of glucose had to be added in the dry shrimp shell assay as compared to the assay with wet shrimp shells, due to the higher amount of total solids in dry shrimp shells.
Mentions: To elucidate whether there exist relevant differences for deproteination of wet or dried P. monodon shells, protein and calcium elimination from the respective abdomen fractions with the proteolytic enrichment cultures M1 and M2 were compared (Figure 1a and b). TKN and protein content of waste shells were determined before each assay. The average TKN and protein content of the shells were 73 mg/g wet weight and 300 mg/g dry weight, respectively as described previously [2]. As shown in Figure 1a, 95% of the protein of 15 g wet weight of shrimp shells (=5.1 g dry weight) was eliminated after 68 h of incubation with enrichment culture M2 and more than 80% was removed with enrichment culture M1. About 80% of the dissolved protein was deaminated during deproteination of wet and dried shrimp shells by both enrichment cultures (Table 1). Although protein removal from dried shrimp shells (Figure 1b) required 120 h (culture M2) or 140 h (culture M1), yet the protein removal rates were much higher than with wet shrimp shells if the dry matter content is taken in consideration. The dry matter amount was 14.1 g and 5.1 g per assay of dried and wet shrimp shells, respectively (Table 2).

Bottom Line: The viscosity of biologically processed chitin was compared with chemically processed chitin.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.Bioprocessing of shrimp shell waste resulted in a chitin with high purity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biology for Engineers and Biotechnology of Wastewater, Karlsruhe Institute of Technology, Am Fasanengarten, Karlsruhe 76131, Germany. mini.bajaj@kit.edu.

ABSTRACT

Background: 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.

Results: 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.

Conclusions: 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.

Show MeSH
Related in: MedlinePlus