Optimal selection of agricultural products to inhibit citrinin production during submerged culture of Monascus anka

Investigating proteome and transcriptome response of Cryptococcus podzolicus Y3 to citrinin and the mechanisms involved in its degradation

Citrinin (CIT) contamination has been reported in agricultural foods and is known to be nephrotoxic to human and animals. In the present study, the proteomes and transcriptomes of C. podzolicus Y3 treated with or without 10 μg/mL CIT were compared by two-dimensional electrophoresis (2-DE) and RNA sequencing, respectively. The proteomics results showed that there were 23 differentially expressed proteins (DEPs), 8 DEPs were up-regulated and 15 DEPs were significantly down-regulated. Transcriptomic analysis showed that 1208 genes were differentially expressed, 551 (43.05%) DEGs were up regulated and 657 (56.95%) were down-regulated. These results showed that the CIT treatment caused DNA damage, oxidative stress and cell apoptosis in C. podzolicus Y3. CIT treatment also activated the defense response (DNA repair and drug resistance biological process, antioxidative activity and TCA cycle) as well as drug metabolism (synthesize the CIT-degrading enzymes) in yeast cells to respond to CIT stress and degrade CIT.

iTRAQ-Based Quantitative Proteomic Analysis Reveals Changes in Metabolite Biosynthesis in Monascus purpureus in Response to a Low-Frequency Magnetic Field

Background: Low-frequency magnetic fields (LF-MFs) dampen the citrinin output by Monascus purpureus in fermentations. The influence of LF-MFs on biosynthesis by M. purpureus was evaluated at the protein level. Methods: Cultures were treated with a 1.6-mT MF from day 0 to day 2 of incubation, and secondary metabolite production was evaluated on the day 12 of incubation. All proteins were extracted from M. purpureus mycelia and subjected to isobaric tags for relative and absolute quantification (iTRAQ) labeling and subsequent liquid chromatography/mass spectrometry (LC-MS/MS) analysis on day 6 of fermentation. Results: There was no difference in biomass between the treated samples and the control. Citrinin production was 46.7% lower, and the yields of monacolin K and yellow, orange, and red pigment were 29.3%, 31.3%, 41.7%, and 40.3% higher, respectively, in the exposed samples compared to the control. Protein expression in M. purpureus under LF-MF treatment was quantified using iTRAQ technology. Of 2031 detected proteins, 205 were differentially expressed. The differentially-expressed proteins were subjected to Gene Ontology (GO) functional annotation and statistical analysis, which revealed that they mainly refer to biological metabolism, translation, antioxidant, transport and defense pathways. Among all the tagged proteins, emphasis was placed on the analysis of those involved in the synthesis of citrinin, pigment and monacolin K was emphasized. Conclusions: LF-MFs affected Monascus secondary metabolism at the protein level, and aggregate data for all the protein profiles in LF-MF-treated Monascus was obtained.

Biocatalytic activity of Monascus mycelia depending on physiology and high sensitivity to product concentration

Cell suspension culture using mycelia as whole cell biocatalyst for production of orange Monascus pigments has been carried out successfully in a nonionic surfactant micelle aqueous solution. Thus, selection of mycelia as whole cell biocatalyst and the corresponding enzymatic kinetics for production of orange Monascus pigments can be optimized independently. Mycelia selected from submerged culture in a nonionic surfactant micelle aqueous solution with low pH 2.5 exhibits robust bioactivity. At the same time, enzymatic kinetic study shows that the bioactivity of mycelia as whole cell biocatalyst is sensitive to high product concentration. Segregation of product from mycelia by cell suspension culture in a nonionic surfactant micelle aqueous solution or peanut oil–water two-phase system is not only necessary for studying the enzymatic kinetics but also beneficial to industrial application of mycelia as whole cell biocatalyst.