A two-step rapid fermentation shrimp paste process based on strain enhancement was developed by inoculating functional strains into shrimp paste in two steps. This improved the drawbacks of traditional fermented shrimp paste products, such as their lengthy fermentation times, high salt contents, and unstable fermentation quality. Single factorial and response surface analyses was employed to optimize the two-step fermentation process, and the physicochemical indices, sensory and volatile components of the rapid fermentation products were analyzed and compared with the uninoculated fermented shrimp paste. The results showed that the optimal process parameters for the one-step fermentation with Cladosporium Z3 were 12 d, 21 ℃ and 3% (V/V) inoculum, and the optimal parameters for the two-step fermentation with Enterococcus faecalis X1 were 4 d, 25 ℃ and 4% (V/V) inoculum. Compared with the uninoculated fermented shrimp paste, the two-step fermented shrimp paste samples with starters had higher amino acid nitrogen (AAN) content, more complete protein hydrolysis and lower total volatile base nitrogen (TVB-N) content, while the two-step fermentation method with intensified starters was able to promote the formation of good flavor and the good quality of shrimp paste.

In this study, a gene encoding serine protease (PmSpr288) from cold-adapted bacterium, namely Planococcus maritimus XJ11, was cloned and overexpressed in Escherichia coli BL21 (DE3). Bioinformatics analysis revealed that PmSpr288 belongs to serine protease S8 superfamily with a classical catalytic triad comprised by the Asp49, His86 and Ser251. Moreover, PmSpr288 was found to be active over broad alkaline pH and low-moderate temperature, and exhibited wide range of protein substrate specificity. In addition, PmSpr288 was able to hydrolyze the meat proteins actin and myosin, and molecular docking results suggested that the crucial interaction between PmSpr288 and actin/myosin complexes was mainly occupied by hydrogen bonds. The muscle protein hydrolysates of silver carp prepared by PmSpr288 was shown to have antioxidant activity via DPPH radical scavenging assay, which presented an IC₅₀ valve of 1.309 mg/mL. In conclusion, these characteristics imply that PmSpr288 has potential biotechnological application prospect for the production of bioactive peptides.

Shrimp sauce, one of the traditional salt-fermented food in China, has a unique flavor that is influenced by the resident microflora. The quality of salt-fermented shrimp sauce was evaluated in this work by determining the total volatile basic nitrogen (TVB-N), the amino acid nitrogen (AAN), organic acid, 5’-nucleotide and free amino acids (FAA). Moreover, the dynamics of microbial diversity during processing was investigated by using high-throughput sequencing technology. The results showed that the AAN, TVB-N, organic acid, 5’-nucleotide and FAA content were in range of 0.93–1.42 g/100mL, 49.91–236.27 mg/100mL, 6.65–20.68 mg/mL, 3.51–6.56 mg/mL and 81.27–102.90 mg/mL. Among the microbial diversity found in the shrimp sauce, Tetragenococcus, Flavobacterium, Polaribacter, Haematospirillum and Staphylococcus were the predominant genera. Correlation analysis indicated that the bacteria Tetragenococcus and Staphylococcus were important in the formation of non-volatile compounds. Tetragenococcus positively correlated with a variety of FAAs; Staphylococcus positively correlated with 5’-nucleotides. The analysis indicated that Tetragenococcus and Staphylococcus were the core genera affecting non-volatile components. These findings indicate the dynamics of the bacterial community and non-volatile components inter-relationships during shrimp sauce fermentation and provide a theoretical basis for improving the fermentation process of shrimp sauce.

Previous studies have suggested that polypeptides extracted from milk, soybean, fish, eggs, and meat possess potential anti-inflammatory effects. To date, few studies have reported the anti-inflammatory function of sturgeon peptides and their underlying mechanisms are unknown. The current study was therefore to determine the anti-inflammatory potential of sturgeon peptides with lipopolysaccharide (LPS)-induced RAW264.7 inflammatory model. Pepsin hydrolysate (PeH) was purified by ultrafiltration and Sephadex G-15 gel filtration chromatography. PeH significantly reduced the inflammatory mediator (NO) and inflammatory cytokines (IL-6、TNF-α and IL-1β) expression in a dose-dependent manner. Moreover, the purified sturgeon peptide (F2) possessed strong antioxidant potential and effectively inhibited DPPH and ABTS free radicals. F2 significantly suppressed the expression of MAPKs, IκBα, and NF-κB p65, indicating that F2 exerted anti-inflammatory influence by the inhibition of MAPK and NF-κB pathways.