Microbial diversity of representative traditional fermented sausages in different regions of China

AIMS

The purpose of this experiment was to study the bacterial diversity of traditional fermented sausages from four typical regions of China (Chengdu, Shenzhen, Changsha and Harbin) and to further evaluate their microbiological safety.

METHODS AND RESULTS

The diversity of the microbiota of the sausages was studied using the Illumina HiSeq platform. The results showed that compared with the highest diversity of fermented bacteria in Guangdong, the bacterial diversity of fermented sausage was the lowest in Sichuan. The percentage of dominant phylum (Firmicutes, Cyanophyta, Proteobacter) were 78·39, 13·13 and 7·14% in SC, 35·47, 30·36 and 28·04% in GD, 54·81, 28·91 and 14·00% in HN, 20·20, 58·16 and 17·31% in HB respectively. The main genus distribution of fermented sausages in different regions is varied, but lactic acid bacteria and cyanobacteria are generally the main ones. Traditional fermented sausages using natural fermentation methods have poor microbiological safety, and pathogenic and spoilage micro-organisms such as Acinetobacter, Brochothrix and Pseudomonas have been detected in all four regions.

CONCLUSIONS

The results in this paper provide a microbiota profile of four typical fermented sausages in China. There is a big difference in the microbiota of sausages in different regions, and the good flavour of traditional Chinese fermented sausage is related closely with the abundant microbial resources, however, the natural fermentation method also expose to the product security threats, including spoilage, pathogenic micro-organisms and biogenic amines, etc. SIGNIFICANCE AND IMPACT OF THE STUDY: The results would offer guidance for industrial fermented sausage production with certain flavour and also improve the microbial resource utilization, and contribute to the control of harmful micro-organisms in traditional fermented sausage.

Influence of the vitamin D status on the early hepatic response to carcinogen exposure in rats

Although 1,25-dihydroxyvitamin D3 has been shown to promote the differentiation of cancer cells and cell lines in vitro, its protective effect against a chemical insult known to induce neoplastic growth in vivo has not been evaluated. The aim of this study was to investigate, in vivo, the influence of the vitamin D status on the early response to an insult known to induce morphological and functional changes leading to hepatocarcinogenesis. The influence of vitamin D status on the susceptibility of rat liver to carcinogenesis was studied after the administration of diethylnitrosamine and 2-acetylaminofluorene, in association with a partial hepatectomy (Solt-Farber protocol), to normal or vitamin D-depleted rats. Preneoplastic foci (gamma-glutamyltranspeptidase-positive and glucose-6-phosphatase-negative) appeared in both groups of animals as early as 1 week after 2-acetylaminofluorene withdrawal and continued to increase during the subsequent weeks. Livers from vitamin D-depleted rats exhibited a significant increase in the number of foci over that observed in normal rats at weeks 1 and 5 after 2-acetylaminofluorene withdrawal. However, the main effect of vitamin D depletion was on focus size, which was found to be significantly greater in vitamin D-depleted rat livers at weeks 2 to 6; focus area (volume fraction) was also found to be consistently larger in livers of vitamin D-depleted rats than in those of normal rats. Labeling of oval cells, a cell compartment possibly associated with the repopulation of the liver parenchyma, was significantly reduced by vitamin D depletion. Control rat livers of both groups showed normal liver histology, and no foci, nodules or oval cells were detected in either group. The present data suggest that vitamin D depletion leads to increased in vivo susceptibility to chemicals known to induce hepatocarcinogenesis. Long-term studies must be conducted to evaluate the effect of vitamin D status on the evolution of preneoplastic foci into frank hepatocellular carcinoma.