Sphingobacterium praediipecoris sp. nov. isolated from effluent of a dairy manure treatment plant

Effect of the Manufacturing Process on the Microbiota, Organoleptic Properties and Volatilome of Three Salmon-Based Products

Lightly preserved seafood products, such as cold-smoked fish and fish gravlax, are traditionally consumed in Europe and are of considerable economic importance. This work aimed to compare three products that were obtained from the same batch of fish: cold-smoked salmon (CSS) stored under vacuum packaging (VP) or a modified atmosphere packaging (MAP) and VP salmon dill gravlax (SG). Classical microbiological analyses and 16S rRNA metabarcoding, biochemical analyses (trimethylamine, total volatile basic nitrogen (TVBN), biogenic amines, pH, volatile organic compounds (VOCs)) and sensory analyses (quantitative descriptive analysis) were performed on each product throughout their storage at a chilled temperature. The three products shared the same initial microbiota, which were mainly dominated by Photobacterium, Lactococcus and Lactobacillus genera. On day 28, the VP CSS ecosystem was mainly composed of Photobacterium and, to a lesser extent, Lactococcus and Lactobacillus genera, while Lactobacillus was dominant in the MAP CSS. The diversity was higher in the SG, which was mainly dominated by Enterobacteriaceae, Photobacterium, Lactobacillus and Lactococcus. Although the sensory spoilage was generally weak, gravlax was the most perishable product (slight increase in amine and acidic off-odors and flavors, fatty appearance, slight discoloration and drop in firmness), followed by the VP CSS, while the MAP CSS did not spoil. Spoilage was associated with an increase in the TVBN, biogenic amines and spoilage associated VOCs, such as decanal, nonanal, hexadecanal, benzaldehyde, benzeneacetaldehyde, ethanol, 3-methyl-1-butanol, 2,3-butanediol, 1-octen-3-ol, 2-butanone and 1-octen-3-one. This study showed that the processing and packaging conditions both had an effect on the microbial composition and the quality of the final product.

Removal of zinc(II) from livestock and poultry sewage by a zinc(II) resistant bacteria

In order to remediate Zn-contaminated livestock and poultry sewage, a zinc-resistant bacterial strain was screened and isolated from the manure of livestock and poultry and identified by molecular biology. The optimal conditions for removing zinc(II) from strain XZN4 were determined by single-factor experiments as follows: within 3 times of repeated use, pH value was 5, initial concentration of zinc(II) was 100 mg/L, the amount of bacteria was 6 g/L, the temperature was 25-30 °C, and the removal equilibrium time was 60 min. Then, through adsorption isotherm model, scanning electron microscope image, energy dispersive spectrum analysis, infrared spectrum analysis and sterilization control experiment, it was found that the removal of zinc(II) by bacteria was single-molecule layer adsorption, which was carried out in coordination with degradation. The influence of different concentrations of copper(II), ammonia nitrogen, phosphorus, and chlortetracycline on the removal of zinc(II) from livestock and poultry sewage by XZN4 strain in the actual application was discussed. The bacteria can reduce the concentration of zinc(II) from the complex livestock and poultry waste water to below the discharge standard, and has a strong environmental tolerance, the highest removal rate reached 88.6% and the highest removal amount reached 10.30 mg/L. The screening and application of XZN4 strain can thus be of great significance for the microbial treatment of zinc(II) in complex livestock and poultry sewage. The results will provide guidance for the microbial remediation of heavy metal pollution.