Research Progress on Gene Synthesis and Anticancer and Lipid-lowering Mechanism of Monacolin K.

Monacolin K (MK), also known as lovastatin (LOV), is a secondary metabolite synthesized by Monascus in the later stage of fermentation and is the main component of functional red yeast rice (RYR). The structure of MK is similar to 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA), and it can competitively bind to 3-hydroxy-3- methylglutaryl coenzyme A reductase (HMGCR), thus reducing the level of blood lipids. MK can affect the expression of MAPK, PI3K/AKT, and NF-κB pathway, prepare conjugates with other compounds, and enhance the sensitivity of cancer cells to chemotherapeutic drugs so as to induce apoptosis of acute myeloid leukemia, prostate cancer, breast cancer, lung cancer, gastric cancer, and liver cancer. Combined with the synthetic route of MK, this paper summarizes the latest lipid-lowering and anticancer mechanism of MK, and provides a reference for the application of MK in medicine.

Transcriptome Analysis of Komagataeibacter europaeus CGMCC 20445 Responses to Different Acidity Levels During Acetic Acid Fermentation.

In the industrial production of high-acidity vinegar, the initial ethanol and acetic acid concentrations are limiting factors that will affect acetic acid fermentation. In this study, Komagataeibacter europaeus CGMCC 20445 was used for acetic acid shake flask fermentation at an initial ethanol concentration of 4.3% (v/v). We conducted transcriptome analysis of K. europaeus CGMCC 20445 samples under different acidity conditions to elucidate the changes in differentially expressed genes throughout the fermentation process. We also analyzed the expression of genes associated with acid-resistance mechanisms. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that the differentially expressed genes were enriched in ribosomes, citrate cycle, butanoate metabolism, oxidative phosphorylation, pentose phosphate, and the fatty acid biosynthetic pathways. In addition, this study found that K. europaeus CGMCC 20445 regulates the gene expression levels of cell envelope proteins and stress-responsive proteins to adapt to the gradual increase in acidity during acetic acid fermentation. This study improved the understanding of the acid resistance mechanism of K. europaeus and provided relevant reference information for the further genetic engineering of this bacterium.

Classification of acetic acid bacteria and their acid resistant mechanism.

Acetic acid bacteria (AAB) are obligate aerobic Gram-negative bacteria that are commonly used in vinegar fermentation because of their strong capacity for ethanol oxidation and acetic acid synthesis as well as their acid resistance. However, low biomass and low production rate due to acid stress are still major challenges that must be overcome in industrial processes. Although acid resistance in AAB is important to the production of high acidity vinegar, the acid resistance mechanisms of AAB have yet to be fully elucidated. In this study, we discuss the classification of AAB species and their metabolic processes and review potential acid resistance factors and acid resistance mechanisms in various strains. In addition, we analyze the quorum sensing systems of Komagataeibacter and Gluconacetobacter to provide new ideas for investigation of acid resistance mechanisms in AAB in the form of signaling pathways. The results presented herein will serve as an important reference for selective breeding of high acid resistance AAB and optimization of acetic acid fermentation processes.