ϵ-Poly-L-lysine (ϵ-PL) is a natural food preservative with high safety to humans and a wide antimicrobial spectra. It was found that ϵ-PL could form precipitates when it contacted to Cu(II) and Zn(II). Thus in this st...
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This study investigated the effect of selected lactic acid bacteria (LAB) fermentation on Goji with flavor, chemical profiles, and bioactivity. Five selected LAB strains were suitable to ferment Goji, and exceeded 8.6...
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Poly-L-lysine（ε-PL） is a natural food preservative with high safety to humans and a wide antimicrobial *** was found that ε-PL could form precipitates when it contacted to Cu（Ⅱ） and Zn（Ⅱ）.Thus in this study,...
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Poly-L-lysine（ε-PL） is a natural food preservative with high safety to humans and a wide antimicrobial *** was found that ε-PL could form precipitates when it contacted to Cu（Ⅱ） and Zn（Ⅱ）.Thus in this study,two complexes of ZnCl and CuCl with ε-poly-L-lysine having molecular weights between 2 and 5 kDa were prepared and characterized by elemental analysis（EA）,atom absorption spectrometry（AAS）,chlorine assay,*** results show that the compositions of two complexes can be expressed as [-NH-（CH2）-CO-]·（ZnCl）_n·2nHO and [-NH-（CH）-CO-]·（CuCl）_n·2nHO（n=6-18）,*** results of FT-IR reveal that the formation of Zn-N and Cu-N coordination bonds.X-RD patterns indicat that the two complexes are new phases different from the raw ε-PL *** the basis of TG-DTA curves,the complexes have a coordination *** the results of the bacteriostatic test,ε-PL-Zn（Ⅱ） and ε-PL-Cu（Ⅱ） have similar antibacterial activity to ligand ε-PL.
Acetic acid bacteria (AAB) are widely used in acetic acid fermentation due to their remarkable ability to oxidize ethanol and high tolerance against acetic acid. In Acetobacter pasteurianus, nucleotide excision repair...
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Acetic acid bacteria (AAB) are widely used in acetic acid fermentation due to their remarkable ability to oxidize ethanol and high tolerance against acetic acid. In Acetobacter pasteurianus, nucleotide excision repair protein UvrA was up-regulated 2.1 times by acetic acid when compared with that without acetic acid. To study the effects of UvrA on A. pasteurianus acetic acid tolerance, uvrA knockout strain AC2005-ΔuvrA, uvrA overexpression strain AC2005 (pMV24-uvrA), and the control strain AC2005 (pMV24), were constructed. One percent initial acetic acid was almost lethal to AC2005-ΔuvrA. However, the biomass of the UvrA overexpression strain was higher than that of the control under acetic acid concentrations. After 6% acetic acid shock for 20 and 40 min, the survival ratios of AC2005 (pMV24-uvrA) were 2 and 0.12%, respectively; however, they were 1.5 and 0.06% for the control strain AC2005 (pMV24). UvrA overexpression enhanced the acetification rate by 21.7% when compared with the control. The enzymes involved in ethanol oxidation and acetic acid tolerance were up-regulated during acetic acid fermentation due to the overexpression of UvrA. Therefore, in A. pasteurianus, UvrA could be induced by acetic acid and is related with the acetic acid tolerance by protecting the genome against acetic acid to ensure the protein expression and metabolism.
To investigate the possibly carcinogenic substance occurring in soy sauce, the furan, 5-hydroxymethylfurfural (HMF) and nitrite, as well as chemical properties, such as total titratable acid, reducing sugars, ethanol,...
To investigate the possibly carcinogenic substance occurring in soy sauce, the furan, 5-hydroxymethylfurfural (HMF) and nitrite, as well as chemical properties, such as total titratable acid, reducing sugars, ethanol, amino nitrogen and total nitrogen, analysis in sixteen commercial soy sauce from the China market were determined using chromatography-mass spectrometry method. There were considerable variations in furan, HMF and nitrite concentrations of different commercial soy sauces. The results showed that the level of furan and 5-hydroxymethylfurfural of the soy sauce studied ranges from15.36 to 119.82 µg/kg and 0.21 to 4.27 mg/kg, respectively, whereas the content of nitrite ranges from 0.04 to 0.73 mg/kg. The results indicated that the level of nitrogen and glucose may have a relationship with formation of furan, 5-HMF and nitrite in soy sauce. It was observed that soy sauce may be an important source of contamination by furan, HMF and nitrite.
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