BackgroundN-acetyl-d-glucosamine (GlcNAc) possesses many bioactivities that have been used widely in many fields. The enzymatic production of GlcNAc is eco-friendly, with high yields and a mild production process compared with the traditional chemical process. Therefore, it is crucial to discover a better chitinase for GlcNAc production from chitin.ResultsA novel chitinase gene (Cmchi1) cloned from Chitinolyticbacter meiyuanensis SYBC-H1 and expressed in Escherichia coli BL21(DE3) cells. The recombinant enzyme (CmChi1) contains a glycosyl hydrolase family 18 catalytic module that shows low identity (12–27%) with the corresponding domain of the well-characterized chitinases. CmChi1 was purified with a recovery yield of 89% by colloidal chitin affinity chromatography, whereupon it had a specific activity of up to 15.3 U/mg. CmChi1 had an approximate molecular mass of 70 kDa after the sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and its optimum activity for colloidal chitin (CC) hydrolysis occurred at pH 5.2 and 50 °C. Furthermore, CmChi1 exhibited kcat/Km values of 7.8 ± 0.11 mL/s/mg and 239.1 ± 2.6 mL/s/μmol toward CC and 4-nitrophenol N,N′-diacetyl-β-d-chitobioside [p-NP-(GlcNAc)2], respectively. Analysis of the hydrolysis products revealed that CmChi1 exhibits exo-acting, endo-acting and N-acetyl-β-d-glucosaminidase activities toward N-acetyl chitooligosaccharides (N-acetyl CHOS) and CC substrates, behavior that makes it different from typical reported chitinases. As a result, GlcNAc could be produced by hydrolyzing CC using recombinant CmChi1 alone with a yield of nearly 100% and separated simply from the hydrolysate with a high purity of 98%.ConclusionThe hydrolytic properties and good environmental adaptions indicate that CmChi1 has excellent potential in commercial GlcNAc production. This is the first report on exo-acting, endo-acting and N-acetyl-β-d-glucosaminidase activities from Chitinolyticbacter species.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1169-x) contains supplementary material, which is available to authorized users.
The aim of this study was to investigate the evolution of some physicochemical properties of fermented Zaopei throughout the fermentation. For each layer of Zaopei, the temperature gradually increased to a maximum after about 2 weeks, and then remained stable for about 15 days before it began to decrease; acidity tended to increase during the entire fermentation, while the starch content decreased throughout the fermentation. The reducing sugar content for all layers reached a maximum after one week and decreased afterwards. Ethanol accumulated with time and reached a peak after 5 weeks for each layer, then tended to decrease but rose again slightly after 7 weeks. The moisture content in the top and middle layers increased gradually and reached saturation after 5 weeks, then remained almost unchanged, while the moisture of the bottom layer increased throughout the fermentation. The ethyl caproate, ethyl acetate and ethyl butyrate content of all layers remained almost constant for the first 2 weeks, then increased gradually and reached a maximum after 6 weeks, and subsequently declined slightly. The ethyl lactate of each layer increased throughout the fermentation. The caproic acid, acetic acid, butyric acid and lactic acid in all of the layers reached the highest level on the sixth week, followed by a continuous decrease until week 8, thereafter followed by a slight increase in trend. Additionally, the qualities of the raw liquor distilled from the different layers of Zaopei were investigated and the results demonstrated that the bottom layer possessed the best quality.
In this study, we propose a novel biological fermentation method to process chitin powder utilizing the bacteria Chitinolyticbacter meiyuanensis SYBC-H1.
In this study, an alkali freeze-thaw pretreatment protocol was investigated to efficiently enhance enzymatic hydrolysis of chitin into N-acetyl glucosamine (GlcNAc) at high concentrations. The optimal conditions for alkali freeze-thaw...
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