Extraction of Chitin From Shrimp Shell by Successive Two-Step Fermentation of Exiguobacterium profundum and Lactobacillus acidophilus

As an environmentally friendly and efficient method, successive two-step fermentation has been applied for extracting chitin from shrimp shells. To screen out the microorganisms for fermentation, a protease-producing strain, Exiguobacterium profundum, and a lactic acid-producing strain, Lactobacillus acidophilus, were isolated from the traditional fermented shrimp paste. Chitin was extracted by successive two-step fermentation with these two strains, and 85.9 ± 1.2% of protein and 95 ± 3% of minerals were removed. The recovery and yield of chitin were 47.82 and 16.32%, respectively. Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy (SEM) were used to characterize the chitin. The crystallinity index was 54.37%, and the degree of deacetylation was 3.67%, which was lower than that of chitin extracted by the chemical method. These results indicated that successive two-step fermentation using these two bacterial strains could be applied to extract chitin. This work provides a suitable strategy for developing an effective method to extract chitin by microbial fermentation.

Allobacillus salarius sp. nov., and Allobacillus saliphilus sp. nov., Isolated from Shrimp Paste (ka-pi) in Thailand

The moderately halophilic, Gram-stain-positive, spore-forming rods, designated SKP4-8T and SKP8-2T isolated from a traditional fermented shrimp paste (Ka-pi), were taxonomic studied based on polyphasic approach. Strain SKP4-8T grew at pH 6.0-9.0 (optimum 7.0), at 25-45°C (optimum 37°C) and in 1-16 % (w/v) NaCl (optimum 5-10). Strain SKP8-2T grew at pH 6.0-9.0 (optimum 8.0), at 25-45°C (optimum 37°C) and in 0-20 % (w/v) NaCl (optimum 3-10 %). The strains contained meso-diaminopimelic acid in cell-wall peptidoglycan and the major menaquinone was MK-7. Strain SKP4-8T contained iso-C15:0, antesio-C15:0 and iso-C17:0; and strain SKP8-2T contained antesio-C15:0, iso-C15:0, iso-C16:0 and antesio-C17:0 as major cellular fatty acids.Phosphatidylglycerol, diphosphatidylglycerol, unknown phospholipids and an unknown glycolipid were detected as major polar lipids. On the basis of 16S rRNA gene sequence analysis, strains SKP4-8T and SKP8-2T belonged to the genus Allobacillus and was closely related to Allobacillus halotolerans LMG 24826T with 98.8 % and 99.3 % similarity, respectively. The comparative genome analysis based on average nucleotide identity (ANI) and digital DNA-DNA hybridization revealed that both strains showed the values below 95 and 70 %, from each other and the Allobacillus halotolerans LMG 24826T, respectively. Based on data from this polyphasic study, strains SKP4-8T and SKP8-2T represent the novel species of the genus Allobacillus and the name Allobacillus salarius sp. nov. was proposed for SKP4-8T (=KCTC 33905T =LMG 30016T =TISTR 2499T); and Allobacillus saliphilus sp. nov. for SKP8-2T (=KCTC 33906T =LMG 29682T =TISTR 2558T).