Extraction of chitin from red crab shell waste by cofermentation with Lactobacillus paracasei subsp. tolerans KCTC-3074 and Serratia marcescens FS-3

For one-step extraction of chitin from red crab shell waste, cofermentation with Lactobacillus paracasei subsp. tolerans KCTC-3074, a lactic-acid-producing bacterium, and Serratia marcescens FS-3, a protease-producing bacterium, was conducted. Fermentation with single strain (L. 3074 or FS-3) was also conducted. At day 7, the pH in L. 3074, FS-3, and L. 3074+FS-3 (1:1) treatment decreased from 6.90 to 3.30, 5.88, and 3.48, respectively. Ash content in the residue after fermentation treatment of crab shells in L. 3074 and L. 3074+FS-3 (1:1) treatment drastically decreased from 41.2% to 3.19 and 1.15%, respectively. In L. 3074+FS-3 (1:1) cofermentation, the level of demineralization was the highest value of 97.2%, but the level of deproteinization in the cofermentation was 52.6% at day 7. Protein content in the treatment of FS-3 alone reduced from 22.4 to 3.62%. These results indicate that cofermentation of the shells using the two strains is efficient and applicable for the one-step extraction of crude chitin from red crab shell waste.

Production of N-acetyl-beta-D-glucosamine from chitin by Aeromonas sp. GJ-18 crude enzyme

A bacterium, GJ-18, having strong chitinolytic activity was isolated from coastal soil. The isolated strain was identified as Aeromonas sp. by morphological and biochemical properties along with 16S rRNA gene sequence. The crude chitinolytic activity of culture supernatants was maximal on the 5th day of culture. Below 45 degrees C, chitin was effectively hydrolyzed to N-acetyl-beta-D-glucosamine (GlcNAc) by Aeromonas sp. GJ-18 crude enzymes, but hydrolysis decreased markedly above 50 degrees C. The optimum pH for enzyme activity was 5.0. TLC and HPLC analysis revealed that, below 45 degrees C, the major reaction product was GlcNAc with a small amount of (GlcNAc)(2) and (GlcNAc)(3), whereas above 50 degrees C the major product was (GlcNAc)(2). When swollen chitin (100 mg) was incubated with crude enzyme preparations (10 U) at 40 degrees C, chitin was hydrolyzed to 83.0 and 94.9% yield of GlcNAc within 5 and 9 days, respectively.