Food and Fermentation Industries >

2025 , Vol. 51 >Issue 22: 247 - 253

DOI: https://doi.org/10.13995/j.cnki.11-1802/ts.041686

Screening of protease-producing Bacillus thuringiensis and its application in chitin preparation

  • KAN Jia ,
  • JIANG Ning ,
  • WANG Xin ,
  • WANG Cheng ,
  • LIANG Liya ,
  • PAN Saikun ,
  • MA Yanhong
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  • 1(College of Ocean Food and Biological Engineering, Jiangsu Ocean University, Lianyungang 222005, China)
    2(Institute of Agro-products Processing, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China)
    3(College of Food Science and Bioengineering, Tianjin Agricultural University, Tianjin 300384, China)

Received date: 2024-11-26

  Revised date: 2025-04-02

  Online published: 2025-12-15

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Abstract

To address the environmental impact of conventional chemical processes, this study developed a sustainable method for chitin extraction.A high protease-producing strain of Bacillus thuringiensis LX-W4 was isolated from naturally fermented crayfish shells and co-fermented with Enterococcus faecalis LX18-9.The fermentation conditions (including initial pH, temperature, crayfish shell addition and duration) were optimised, and the optimal parameters were determined to be pH 6.0, fermentation temperature 40 ℃, crayfish shell addition 6% and fermentation for 4 days.Under these conditions, the protease activity of LX-W4 was 86.02 U/mL and the deproteinisation rate reached 95.21%.Structural characterisation using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) confirmed that LX-W4 had an α-crystal structure with a deacetylation degree of 15% and a crystallinity index of 84.8%.The surface morphology was smooth, flat, and porous, with higher purity and structural integrity compared with chemically extracted chitin.Compared with the traditional chemical method, the microbial fermentation method better preserved the molecular structure of chitin and improved the purity of the product.This study establishes a novel fermentation process for chitin extraction from crayfish shells, which provides a viable method for the high-value utilisation and recycling of crayfish by-products.The results of the study highlight the potential of microbial fermentation as an environmentally friendly alternative method for chitin production.

Key words： crayfish shell; protease; strain screening; fermentation; chitin

Cite this article

KAN Jia , JIANG Ning , WANG Xin , WANG Cheng , LIANG Liya , PAN Saikun , MA Yanhong . Screening of protease-producing Bacillus thuringiensis and its application in chitin preparation[J]. Food and Fermentation Industries, 2025 , 51(22) : 247 -253 . DOI: 10.13995/j.cnki.11-1802/ts.041686

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