Identification of the high-yield monacolin K strain from Monascus spp. and its submerged fermentation using different medicinal plants.

BACKGROUND: Medical plants confer various benefits to human health and their bioconversion through microbial fermentation can increase efficacy, reduce toxicity, conserve resources and produce new chemical components. In this study, the cholesterol-lowering monacolin K genes and content produced by Monascus species were identified. The high-yield monacolin K strain further fermented with various medicinal plants. The antioxidant and anti-inflammatory activities, red pigment and monacolin K content, total phenolic content, and metabolites in the fermented products were analyzed. RESULTS: Monacolin K was detected in Monascus pilosus (BCRC 38072), and Monascus ruber (BCRC 31533, 31523, 31534, 31535, and 33323). It responded to the highly homologous mokA and mokE genes encoding polyketide synthase and dehydrogenase. The high-yield monacolin K strain, M. ruber BCRC 31535, was used for fermentation with various medicinal plants. A positive relationship between the antioxidant capacity and total phenol content of the fermented products was observed after 60 days of fermentation, and both declined after 120 days of fermentation. By contrast, red pigment and monacolin K accumulated over time during fermentation, and the highest monacolin K content was observed in the fermentation of Glycyrrhiza uralensis, as confirmed by RT-qPCR. Moreover, Monascus-fermented medicinal plants including Paeonia lactiflora, Alpinia oxyphylla, G. uralensis, and rice were not cytotoxic. Only the product of Monascus-fermented G. uralensis significantly exhibited the anti-inflammatory capacity in a dose-dependent manner in lipopolysaccharide-induced Raw264.7 cells. The metabolites of G. uralensis with and without fermentation (60 days) were compared by LC/MS. 2,3-Dihydroxybenzoic acid, 3,4-dihydroxyphenylglycol, and 3-amino-4-hydroxybenzoate were considered to enhance the antioxidant and anti-inflammatory ability. CONCLUSIONS: Given that highly homologous monacolin K and citrinin genes can be observed in Monascus spp., monacolin K produced by Monascus species without citrinin genes can be detected through the complementary methods of PCR and HPLC. In addition, the optimal fermentation time was important to the acquisition of antioxidants, red pigment and monacolin K. These bioactive substances were significantly affected by medicinal plants over fermentation time. Consequently, Monascus-fermented G. uralensis had a broad spectrum of biological activities.

Inspecting the genome sequence and agarases of Microbulbifer pacificus LD25 from a saltwater hot spring.

Neoagaro-oligosaccharides prepared by agar hydrolysis have various application fields, including the pharmaceutical, cosmetic, and food industries. In this study, an agarolytic strain was isolated from a saltwater hot spring and identified as Microbulbifer pacificus LD25 by 16S rRNA. The whole genome sequence of M. pacificus LD25 was obtained. It had a size of 4.27 Mb and comprised 3062 predicted genes in 37 contigs with a G+C content of 58.0%. Six agarases were annotated and classified into three families, namely, GH16 (AgaL1), GH86 (AgaL2, AgaL3), and GH50 (AgaL4, AgaL5, AgaL6), which shared 75-96% identities with unpublished hypothetical proteins and agarases. AgaL1, AgaL4, and AgaL6 can be successfully expressed and purified in Escherichia coli. AgaL1 and AgaL4 displayed a significantly agarolytic capability, whereas AgaL6 exhibited a rarely detectable enzymatic activity. The optimal temperature and pH required for the activity of AgaL1 and AgaL4 was 50°C and 60°C, respectively, at pH 7. The specific activities of AgaL1 and AgaL4 were achieved at 16.8 and 9.6 U per mg of protein. Both agarases were significantly inhibited in the presence of EDTA, MgO, ZnCl2, and H2O2. However, AgaL1 was resistant to 0.1% SDS and AgaL4 was slightly activated by CaCl2. Substrate hydrolysis detected by LC-MS/MS analysis indicated that neoagarobiose was the main product during AgaL1 and AgaL4 catalysis. Furthermore, AgaL4 was thermostable and retained over 93% of its relative activity after pre-incubation at 70°C for 180 min. Consequently, M. pacificus LD25 has a potential for agarase production in E. coli and industrial applications.

Selection of an effective red-pigment producing Monascus pilosus by efficient transformation with aurintricarboxylic acid.

The filamentous fungus Monascus pilosus was genetically transformed with a reporter plasmid, pMS-1.5hp, by aurintricarboxylic acid (ATA) treatment to obtain an efficient red-pigment producing mutant. The transformation efficiency of Monascus pilosus was higher with the ATA-treatment than with either a non-restriction-enzyme-mediated integration (REMI) or a REMI method. This valid and convenient random mutagenesis method shows that ATA can be applied in fungi for efficient genetic transformation.

Characterization and expression of the antifungal protein from Monascus pilosus and its distribution among various Monascus species.

Monascus species are traditionally used for food preservation. This study used the disc diffusion method to verify the antifungal activity of protein extracted from Monascus pilosus BCRC38072 against 15 fungal pathogens. An antifungal protein, designated as MAFP1, was successfully purified and confirmed through N-terminal sequencing. To further explore the antifungal gene, a mafp1 gene that is similar to that of PgAFP from Penicillium chrysogenum was cloned from M. pilosus BCRC38072. According to the N-terminal sequencing and in silico analysis, the signal peptide was assumed to have 18 amino acids and the mature MAFP1 to contain 58 peptides. Moreover, the mafp1 gene was recognized in Monascus ruber, Monascus barkeri, Monascus floridanus, and Monascus lunisporas through polymerase chain reaction and DNA sequencing and showed high homology. By contrast, the mafp1 gene was absent in Monascus kaoliang, Monascus purpureus, and Monascus sanguineus. In addition, the mafp1 gene with N-terminal polyhistidine fusion was overexpressed in Escherichia coli. However, the antifungal activity of recombinant MAFP1 was significantly lower than that of native MAFP1. According to the properties of MAFP1, Monascus species may have food preservation applications.