Xiaofu Wang,Yunsong Zhao,Sufang Zhang,Xinping Lin,Huipeng Liang,Yingxi Chen,Chaofan Ji
Biogenic amines (BAs) are produced by microbial decarboxylation in various foods. Histamine and tyramine are recognized as the most toxic of all BAs. Applying degrading amine enzymes such as multicopper oxidase (MCO) is considered an effective method to reduce BAs in food systems. This study analyzed the characterization of heterologously expressed MCO fromL. sakeiLS. Towards the typical substrate 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), the optimal temperature and pH for recombinant MCO (rMCO) were 25 °C and 3.0, respectively, with the specific enzyme activity of 1.27 U/mg. Then, the effect of different environmental factors on the degrading activity of MCO towards two kinds of BAs was investigated. The degradation activity of rMCO is independent of exogenous copper and mediators. Additionally, the oxidation ability of rMCO was improved for histamine and tyramine with an increased NaCl concentration. Several food matrices could influence the amine-oxidizing activity of rMCO. Although the histamine-degrading activities of rMCO were affected, this enzyme reached a degradation rate of 28.1% in the presence of surimi. Grape juice improved the tyramine degradation activity of rMCO by up to 31.18%. These characteristics of rMCO indicate that this enzyme would be a good candidate for degrading toxic biogenic amines in food systems.Keywords:Lactobacillus sakei;biodegradation;multicopper oxidase;food matrices;biogenic amines
Ling Li,Yanxin Huang,Ruya Tan,Danli Wang,Tinglan Yuan,Gongshuai Song,Hyunbin Seong,Jinyan Gong
To enhance the stability and intestinal delivery of the probiotic Lactobacillus sakei J15, a multilayer microencapsulation system was developed using layer-by-layer (LBL) technology, using milk protein-hyaluronic acid (HA) conjugates (casein–HA or β-lactoglobulin–HA) and chitosan (CHI). The microcapsules exhibited high encapsulation efficiency (up to 98.65%) and significantly improved probiotic viability under harsh conditions, including acid, bile salt, simulated gastrointestinal digestion, and heat. Electrostatic interaction was confirmed as the main force binding the amino groups in the conjugate to the carboxyl groups of CHI, and the surface charge of the samples reversed as a zigzag pattern whenever another outermost layer was added. The (CHI/CN–HA/CHI)3 and (CHI/β-Lg–HA/CHI)3 microcapsules exhibited the best adhesion to Caco-2 cells, reaching 24.47 and 26.71 CFU/cell, respectively. Microcapsules with two or four layers (milk protein-HA as the outer layer) showed superior resistance to environmental stresses, while three-layer capsules (chitosan as the outer layer) exhibited the strongest adhesion to Caco-2 cells.
Yong-Xiang Wu,Xun Zhou,Benwang Zhou,Chao Li,Peng Cui,Manhuan Cheng,Yang Wang,Xinsong She
Presently, Cu(OH) 2 nanowire arrays@Cu Foam (Cu(OH) 2 –NWA@Cu Foam) nanostructure has been confirmed to possess an excellent capacity of nonenzymatical electroanalysis of histamine (His). Based on Cu(OH) 2 –NWA@Cu Foam electrode, electrochemical investigations elucidated electron transfer kinetics principles of electrooxidation of His. Substantially, it was realized that a four–electron–transferring dehydrogenation was involved in diffusion–controlled electrooxidation of His, contributing tremendously to establishing as–proposed mechanization of His electrooxidation. At optimal conditions, Cu(OH) 2 –NWA@Cu Foam electrode reflected excellent electrochemical performance such as sensitivity of 3.089 mA mM –1 cm –2 , limit of determination of 94 nM, respond time of 1.6 s and linear respond rang of 0.5–1250 μM. The outperformed electroanalytical performance can be physically explicated by the dedications from larger exposed surface area, bigger interface–hydrophilicity–deduced His diffusion coefficient and less charge transfer resistance. Moreover, the outstanding selectivity, stability and reproducibility of Cu(OH) 2 –NWA@Cu Foam electrode ensured its practical effectiveness in regulating real His levels in fermented mandarin fish. Compared with control group, the mandarin fish by inoculating Lactobacillus sakei subsp . sakei delivered less His contents, deducing that inoculation of Lactobacillus sakei subsp . sakei can effectively depress His generation during fermentation process. Eventually, the one–step as–established Cu(OH) 2 –NWA@Cu Foam nanostructure positioned itself as an upcoming possibility to pursue commercialized utilization.
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