Bacillus amyloliquefaciens belongs to the genus Bacillus and family Baciliaceae. It is ubiquitously found in food, plants, animals, soil, and in different environments. In this review, the application of B. amyloliquefaciens in probiotic and prebiotic microbes in fermentation, synthesis, and hydrolysis of food compounds is discussed as well as further insights into its potential application and gaps. B. amyloliquefaciens is also a potential microbe in the synthesis of bioactive compounds including peptides and exopolysaccharides. In addition, it can synthesize antimicrobial compounds (e.g., Fengycin, and Bacillomycin Lb), which makes its novelty in the food sector greater. Moreover, it imparts and improves the functional, sensory, and shelf life of the end products. The hydrolysis of complex compounds including insoluble proteins, carbohydrates, fibers, hemicellulose, and lignans also shows that B. amyloliquefaciens is a multifunctional and potential microbe which can be applied in the food industry and in functional food processing.

Here, molecular docking simulation was used to predict and compare interactions between a recombinant Trametes sp. C30 laccase from Saccharomyces cerevisiae and four aflatoxins (AFB 1 , AFB 2 , AFG 1 , and AFG 2 ) as well as their degradation at a molecular level. The computational result of docking simulation indicates that each of the aflatoxins tested can interact with laccase with a binding ability of AFB 1 >AFG 2 >AFG 1 >AFB 2 . Simultaneously, it also demonstrated that aflatoxin B 1 , B 2 , G 1 , G 2 may interact near the T1 copper center of the enzyme through H-bonds and hydrophobic interactions with amino acid residues His481 and Asn288; His481; Asn288, and Asp230; His481 and Asn288. Biological degradation test was performed in vitro in the presence of a recombinant laccase. Degradation increased as incubation time increased from 12 to 60 hr and the maximum degradation obtained for AFB 1 , AFB 2 , AFG 1 , and AFG 2 was 90.33%, 74.23%, 85.24%, and 87.58%, respectively. Maximum degradation of aflatoxins was determined with a total activity 3 U laccase at 30°C in 0.1 M phosphate buffer, pH 5.7 after 48-hr incubation. The experimental results are consistent with that of docking calculation on the biological degradation test of four aflatoxins by laccase.Practical Application: In this study, the degradation efficiencies of laccase for B and G series of aflatoxins were determined by computer simulation and verified by performing in vitro experiments. It can provide reference for rapid screening of aflatoxin degradation-related enzymes.

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Spermidine is a biologically active polyamine with extensive application potential in functional foods. However, previously reported spermidine titers by biosynthesis methods are relatively low, which hinders its industrial application. To improve the spermidine titer, key genes affecting the spermidine production were mined to modify Bacillus amyloliquefaciens. Genes of Sadenosylmethionine decarboxylase (speD) and spermidine synthase (speE) from different microorganisms were expressed and compared in B. amyloliquefaciens. Therein, the speD from Escherichia coli and speE from Saccharomyces cerevisiae were confirmed to be optimal for spermidine synthesis, respectively. Gene and amino acid sequence analysis further confirmed the function of speD and speE. Then, these two genes were co-expressed to generate a recombinant strain B. amyloliquefaciens HSAM2(PDspeD-SspeE) with a spermidine titer of 105.2 mg/L, improving by 11.0-fold compared with the control (HSAM2). Through optimization of the fermentation medium, the spermidine titer was increased to 227.4 mg/L, which was the highest titer among present reports. Moreover, the consumption of the substrate S-adenosylmethionine was consistent with the accumulation of spermidine, which contributed to understanding its synthesis pattern. In conclusion, two critical genes for spermidine synthesis were obtained, and an engineering B. amyloliquefaciens strain was constructed for enhanced spermidine production.

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