Mechano-Enzymatic Degradation of the Chitin from Crustacea Shells for Efficient Production of N-acetylglucosamine (GlcNAc).

Chitin, the second richest polymer in nature, is composed of the monomer N-acetylglucosamine (GlcNAc), which has numerous functions and is widely applied in the medical, food, and chemical industries. However, due to the highly crystalline configuration and low accessibility in water of the chitin resources, such as shrimp and crab shells, the chitin is difficult utilize, and the traditional chemical method causes serious environment pollution and a waste of resources. In the present study, three genes encoding chitinolytic enzymes, including the N-acetylglucosaminidase from Ostrinia furnacalis (OfHex1), endo-chitinase from Trichoderma viride (TvChi1), and multifunctional chitinase from Chitinolyticbacter meiyuanensis (CmChi1), were expressed in the Pichia pastoris system, and the positive transformants with multiple copies were isolated by the PTVA (post-transformational vector amplification) method, respectively. The three recombinants OfHex1, TvChi1, and CmChi1 were induced by methanol and purified by the chitin affinity adsorption method. The purified recombinants OfHex1 and TvChi1 were characterized, and they were further used together for degrading chitin from shrimp and crab shells to produce GlcNAc through liquid-assisted grinding (LAG) under a water-less condition. The substrate chitin concentration reached up to 300 g/L, and the highest yield of the product GlcNAc reached up to 61.3 g/L using the mechano-enzymatic method. A yield rate of up to 102.2 g GlcNAc per 1 g enzyme was obtained.

Niches and interspecific association of major shrimp and crab species in Pishan waters of Zhejiang Province, China.

Based on the fishery resource investigation data in Pishan waters of Zhejiang coastal area in November of 2015 (autumn), February (winter), May (spring) and August (summer) of 2016, we analyzed the spatio-temporal niche characteristics and interspecific association of the domi-nant shrimp and crab species using the methods of niche test, variance ratio, chi-square test, Spearman test and redundancy analysis. A total of 34 shrimp and crab species belonging to 14 families and 20 genera were identified. Among them, 10 species were collected in all the four seasons. Dominant species were Parapenaeopsis hardwickii, Exopalaemon carinicauda and Portunus trituberculatus. The temporal, spatial and spatio-temporal niche breadths of the major shrimp and crab species ranged from 0.03-1.34, 2.07-3.63 and 0.08-4.64, respectively. The cluster analysis of niche breadths suggested that all the species could be divided into narrow, medium and wide niche breadth groups under the 90% similarity level. In addition, the spatio-temporal niche overlap values of the major species in Pishan Sea were mainly at low level (68.9% of the species's Qik<0.3), implying little interspecific competition for resource utilization. The analysis of variance ratio showed that the major shrimp and crab species were mainly positively correlated, with 11.1% of the species showing significantly positive association. The JI index, OI index and Spearman test all showed the relationship between major shrimp and crab species tended to be positive correlation as a whole. Redundancy analysis showed that surface temperature, bottom temperature, and surface salinity were the main environmental factors affecting the distribution of shrimp and crab species in Pishan waters.

High production of cold-tolerant chitinases on shrimp wastes in bench-top bioreactor by the Antarctic fungus Lecanicillium muscarium CCFEE 5003: bioprocess optimization and characterization of two main enzymes.

The Antarctic fungus Lecanicillium muscarium CCFEE-5003 was preliminary cultivated in shaken flasks to check its chitinase production on rough shrimp and crab wastes. Production on shrimp shells was much higher than that on crab shells (104.6±9.3 and 48.6±3.1U/L, respectively). For possible industrial applications, bioprocess optimization was studied on shrimp shells in bioreactor using RSM to state best conditions of pH and substrate concentration. Optimization improved the production by 137% (243.6±17.3). Two chitinolytic enzymes (CHI1 and CHI2) were purified and characterized. CHI1 (MW ca. 61kDa) showed optima at pH 5.5 and 45°C while CHI2 (MW ca. 25kDa) optima were at pH 4.5 and 40°C. Both enzymes maintained high activity levels at 5°C and were inhibited by Fe(++), Hg(++) and Cu(++). CHI2 was strongly allosamidin-sensitive. Both proteins were N-acetyl-hexosaminidases (E.C. 3.2.1.52) but showed different roles in chitin hydrolysis: CHI1 could be defined as "chitobiase" while CHI2 revealed a main "eso-chitinase" activity.