Covering: up to June 2018 Understanding the biosynthetic mechanisms that generate the astounding structural complexity and variety of fungal secondary metabolites (FSMs) remains a challenge. As an example, the biogenesis of the Monascus azaphilone pigments (MonAzPs) has remained obscure until recently despite the significant medical potential of these metabolites and their long history of widespread use as food colorants. However, a considerable progress has been made in recent years towards the elucidation of MonAzPs biosynthesis in various fungi. In this highlight, we correlate a unified biosynthetic pathway with the diverse structures of the 111 MonAzPs congeners reported until June 2018. We also discuss the origins of structural diversity amongst MonAzPs analogues and summarize new research directions towards exploring novel MonAzPs. The case of MonAzPs illuminates the various ways that FSMs metabolic complexity emerges by the interplay of biosynthetic pathway determinism with metabolic and chemical serendipity.

The nutrition and flavor of shrimp paste came from hydrolyzation by enzymes that were produced by microorganisms. The salt‐tolerant strain Virgibacillus halodenitrificans ST‐1 isolated from shrimp paste was studied and used in the fermentation of shrimp paste. The strain and the protease produced by ST‐1 were investigated. The optimum pH of the protease was 8.0, and the reaction temperature was 30°C. The protease showed high activity in the range of pH (5.0–11.0) and NaCl concentration (1%–15%). Divalent cations such as Ba²⁺, Ca²⁺, Mg²⁺, Mn²⁺, and Si²⁺ could enhance the protease activity. Residual activity of protease was more than 90% when it was incubated with PMSF and H₂O₂. Also, the enzyme retained more than 90% of initial activity after it was incubated with organic solvents. Variety of natural proteins could be substrates of the protease. By analyzing the release rate of free amino acids, it was predicted that the cleavage sites of the protease were mainly Glu, Asp, Gly, Leu, and Lys. Moreover, the hydrolysates of the protease had antioxidant activity, especially for DPPH and superoxide anion radical scavenging. The strain ST‐1 and the protease both were excellent candidates for food industries.

Monascus pigments (MPs) and monacolin K (MK) are important secondary metabolites produced by Monascus spp. This study aimed to investigate the effect of soybean protein isolate (SPI) on the biosynthesis of MPs and MK based on the analysis of physiological indicators, transcriptomes, and metabolomes. The results indicated that the growth, yellow MPs, and MK production of Monascus pilosus MS-1 were significantly enhanced by SPI, which were 8.20, 8.01, and 1.91 times higher than that of the control, respectively. The utilization of a nitrogen source, protease activity, the production and utilization of soluble protein, polypeptides, and free amino acids were also promoted by SPI. The transcriptomic analysis revealed that the genes mokA, mokB, mokC, mokD, mokE, mokI, and mokH which are involved in MK biosynthesis were significantly up-regulated by SPI. Moreover, the glycolysis/gluconeogenesis, pyruvate metabolism, fatty acid degradation, tricarboxylic acid (TCA) cycle, and amino acid metabolism were effectively up-regulated by SPI. The metabolomic analysis indicated that metabolisms of amino acid, lipid, pyruvate, TCA cycle, glycolysis/gluconeogenesis, starch and sucrose, and pentose phosphate pathway were significantly disturbed by SPI. Thus, MPs and MK production promoted by SPI were mainly attributed to the increased biomass, up-regulated gene expression level, and more precursors and energies.

The implementation of innovative techniques to achieve low-salt strategies in cured products is a critical issue faced by the food industry. This study aimed to investigate the impact of ultrasound treatment on the quality of the low-salt air-dried fish. The results showed that compared to traditional liquid curing, ultrasound-assisted curing significantly increased the NaCl transfer rate, improved tenderness, and improved water retention and in vitro digestibility (p < 0.05). Microscopic observations revealed that ultrasound treatment substantially disrupted the muscle fiber structure, enlarging the spaces between fibers. Furthermore, ultrasound-assisted curing led to the unfolding of the spatial structure of myofibrillar proteins, enhanced intermolecular hydrophobic interactions, and promoted protein oxidation (p < 0.05), which are fundamental reasons for the improvement in fish quality. Thus, ultrasound treatment had a positive effect on fish curing, with the optimal parameters identified as 590 W for 78 min. Overall, the findings of this study provide evidence for the application of low-salt processing technology in fish products.