Purpose This study sought to employ the response surface methodology (RSM) to investigate factors that affect Bacillus amyloliquefaciens X8 bacteriostasis. Methods Design Expert 8.0.6 was used to perform multiple regression fitting and create antimicrobial mathematical models to optimize the antimicrobial effect of Bacillus amyloliquefaciens X8. A Shodex Protein KW-2004 gel column and a C18 column coupled with a high-performance liquid chromatography (HPLC) system were used to separate and

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... y the antimicrobial substances extracted from Bacillus amyloliquefaciens X8 (X8-AS). An Agilent 6410 Triple Quad LC/MS system and Nicolet-is10 system were used to analyze X8-AS via liquid chromatography mass spectrometry (LC-MS) and infrared spectroscopy (IR). Results The results demonstrated that the optimum antimicrobial conditions for Bacillus amyloliquefaciens X8 (at which antimicrobial activity was increased by 22.3%) were pH 6, 30 ℃, and 36 h of incubation. Conclusion The results showed that the relative molecular weight of X8-AS was 1413.5 Da. After searching through the infrared spectrum material library, X8-AS was found to be highly similar to chondroitin sulfate.