Although coagulase-negative Staphylococcus (CNS) with technological activities plays a key role in fermented sausage flavour and nutrient production, the molecular mechanism of these activities remains elusive. In this study, 18 CNS strains with high proteolytic activity were isolated from Chinese Dong fermented pork (Nanx Wudl), and their technological and transcriptomic properties were investigated. After biochemical identification and genetic analysis, their technological properties, including nitrate reductase, catalase, antioxidant, and lipolytic activities, as well as their growth under varying temperatures, salt concentrations, and pH levels, were evaluated. Their aroma-producing potential was also determined in a model medium resembling fermented sausages. Transcriptomic analysis was performed using the most promising isolates. Biochemical identification and 16S rDNA sequencing revealed that the 18 Staphylococcus strains belonged to S. xylosus, S. saprophyticus, S. carnosus, S. sciuri, and S. equorum. In terms of technological properties, 16 strains showed a nitrate-reducing ability, while 11 strains had a lipolytic activity. All strains exhibited superoxide dismutase (SOD) and catalase activities; four strains displayed an SOD activity of > 50%. They also tolerated 10% NaCl and 150 mg/kg of nitrite. They showed significant differences in ketone and acid production. The transcriptomic analysis of S. xylosus strains Sx3 and Sx6, which were selected because of their excellent enzymatic activities and aroma-producing ability, revealed the remarkable effect of genes related to pyruvate catabolism and amino acid metabolism on aroma generation. Therefore, this study provided valuable insights into the metabolic mechanisms underlying the technological properties of CNS and identified promising candidates as starter cultures in fermented sausage manufacturing.

The increase in human population has led to imminent pressures to develop new edible proteins with decreased environmental footprints. The most promising approach involves the production of single cell protein (SCP) from yeasts, which have been utilized in a wide variety of foods for thousands of years. In this study, 102 yeast strains isolated from traditional fermented pork (Nanx wudl) were investigated for their potential as SCP producer for the first time. Based on preliminary screening, Saccharomyces cerevisiae Y70 and Candida parapsilosis H5Y13, both showing high protein content and excellent growth capability, were selected for further analysis via 4D-DIA Proteomics technology. Proteomic analysis indicated that the oxidative metabolism pathways, including TCA cycle, oxidative phosphorylation and pentose phosphate pathway, may have a significant impact on global protein synthesis and production. This study provides useful information for selecting SCP-producing yeast from Chinese fermented meat products and contribute to a deeper understanding of the underlying metabolic mechanisms behind global protein synthesis in yeast. Furthermore, these findings also provide potential molecular targets for genetic engineering modifications in yeast, aimed at constructing highly efficient cell factories for protein production.

Yeasts play a critical role in the flavor formation of dry-cured ham. In this study, 41 yeast isolates from the dry-cured ham at different processing stages were evaluated for their technological properties. Debaryomyces hansenii was the most dominant yeast and has been detected at each phase of dry-cured ham, followed by Candida zeylanoides which was mainly detected in salting phase. Yarrowia bubula and Yarrowia alimentaria were found at the first two-phase of dry-cured ham. All isolates of yeast showed enzymatic activities against milk protein and tributyrin, while only 4 strains displayed proteolytic activity on meat protein. Yeast strains were grown in a meat model medium and volatile compounds were identified. The result showed that inoculated yeast strains could promote the production of volatiles and there were significant differences among strains. D. hansenii S25 showed the highest production of volatile compounds, followed by the strain C. zeylanoides C4. D. hansenii S25 was the highest producer of alcohols showing the highest production of benzeneethanol and 3-(methylthio)-1-propanol. Based on OAV and PLS analysis, D. hansenii S25 was strongly correlated with overall flavor and key volatile compounds of dry-cured ham, which could be selected as potential starter cultures.

Yeasts are one of the predominant microbial groups in fermented meats. In this study, yeast communities of Chinese Dong fermented pork (Nanx Wudl) were investigated and the technological properties of 73 yeast isolates were evaluated. Through culture-dependent and high-throughput sequencing methods, the main yeast species identified included Pichia membranifaciens, Kazachstania bulderi, Millerozyma farinosa, Candida zeylanoides, Kazachstania exigua, Candida parapsilosis and Saccharomyces cerevisiae. Among these yeasts, P. membranifaciens, M. farinosa, K. exigua and K. bulderi were detected in fermented meats for the first time. A total of 73 yeast isolates was investigated for their lipolytic and proteolytic activities. All yeast species showed lipolytic activity, while proteolytic activity against meat protein was only detected in S. cerevisiae. Assay of aroma-producing potential was performed in a model simulating fermented sausage condition. Inoculation of yeast strains increased volatiles production, especially esters and alcohols. The highest ester production was observed in S. cerevisiae Y70 strain, followed by K. exigua Y12 and K. bulderi Y19. C. zeylanoides Y10 and S. cerevisiae Y70 were the highest producers of benzeneethanol and 3-methyl-1-butanol. S. cerevisiae Y70 with its highest production of branched alcohols and esters could be a promising candidate as aroma enhancer in the manufacture of fermented sausages.