Convenient access to L-3,4,5-trioxygenated phenylalanine compounds from L-tyrosine

Microbiota dynamics and metabolic mechanisms in fermented sausages inoculated with Lactiplantibacillus plantarum and Staphylococcus xylosus

Lactiplantibacillus plantarum and Staphylococcus xylosus are common starters for fermented sausages. Several studies have demonstrated the impact of these two strains on the quality of fermented sausages. However, the mechanism underlying the effects of these two microorganisms on co-cultivation in sausages remains unclear. This study aimed to investigate the effects of inoculation with various combinations of starters on the microbial communities and metabolic profiles of fermented sausages. High-throughput sequencing revealed that, during sausage fermentation, Firmicutes was the dominant bacterial phylum, and the primary microorganisms were Lactococcus, Staphylococcus, Lactobacillus, and Pseudomonas. On the last day of fermentation, the highest abundance of Staphylococcus was observed in the co-inoculation group. Furthermore, inoculated fermentation effectively inhibited the growth of pathogenic and spoilage bacteria. Metabolomic analysis of the four groups of samples identified 208 metabolites in positive ion mode and 109 in negative ion mode. A total of 31 differential metabolites were identified (P < 0.05, variable importance in the projection >1.5), primarily benzene and substituted derivatives, carboxylic acids and derivatives, and fatty acyls. Five crucial differential metabolites (subaphylline, naringenin, 1-hexadecanol, beta-alanyl-L-lysine, and 3'-AMP) were identified as potential biomarkers for fermented sausages. Key differential metabolite metabolic pathways indicated that L. plantarum YR07 dominated in metabolite regulation during sausage fermentation, and S. xylosus Y-18 downregulated the fatty acid degradation pathway, which also affected the metabolism of fermented sausages. Co-cultivation of the two bacteria exhibited a synergistic effect on the metabolism of the fermented sausages. This study offers further insights into improving the quality of fermented sausages, thereby establishing a theoretical foundation for the production of excellent fermenters.

A new method to recover L-tyrosine from E. coli fermentation broth

Although the production of L-tyrosine by recombinant Escherichia coli has been widely reported, L-tyrosine recovery from the fermentation broth has been rarely reported. Methods to recover L-tyrosine from the broth after alkaline lysis of the bacterial cells have been described. However, the broth becomes viscous and dark following cell lysis, making further extraction and purification difficult. Here, a new method for L-tyrosine extraction and purification from the fermentation broth without the lysis of bacteria is reported. First, acids, rather than bases, were used to dissolve L-tyrosine in the broth without causing lysis of the bacterial cells. E. coli cells in the broth were then removed through centrifugation. Activated carbon was then used to decolorize the supernatant containing L-tyrosine. Finally, sodium hydroxide was added to the clarified L-tyrosine solution for isoelectrocrystallization. L-tyrosine was obtained after filtration and drying. The recovery yield of L-tyrosine was 92%, and the purity was >98.5%, indicating high efficiency of the new method of L-tyrosine recovery from fermented broth. Furthermore, the method provides a reference for the extraction of guanosine, inosine, hypoxanthine, and other biological fermentation products.