Monascus pilosus NBRC4520 was selected for functional fermented food inoculation for its high lovastatin and low citrinin production with a deep-red color. For koji (mold rice) with high lovastatin production, separation of the growth phase and lovastatin production phase by shifting the temperature from 30 to 23 degrees C increased lovastatin production by nearly 20 times compared to temperature-constant cultivation. In addition, citrinin was not produced even in the lovastatin production phase, although the pigment was increased. With temperature-shift cultivation, 225 microg lovastatin/g dry koji was produced in 14 days without citrinin.
Vanillin is valuable and popular flavor used in foods and cosmetics. Many bacteria species have the ability to decarboxylate substituted cinnamic acids in order to form vanillin. However, the phenolic biotransformation including vanillin production in a common fungus, the Aspergillus luchuensis, which is used in distilled beverages, has not yet been clarified. This study focused on elucidating the vanillin production due to phenolic biotransformation in A. luchuensis during fermentation. The phenolic metabolites were extracted by a solid phase column and they were determined using on LC/MS and LC/MS/MS in a selective ion mode. As a result, ferulic acid, vanillin and vanillic acid, were detected in the rice koji fermentationed by A. luchuensis and also fermentated with yeast. In addition, the accurate molecular formula of vanillin glucoside (C14H17O8, 313.0927, (M-H)− and its production ions was also determined by HRESI-mass spectrometry. Based on the results including the phenolic metabolites and related genes found in A. luchuensis genome, this study proposed the vanillin production mechanism due to the side chain cleavage of ferulic acid through Coenzyme A (CoA) and feruloyl-CoA hydratase/lyase, to form vanillin and acetyl-COA. In this study, another possible vanillin production pathway also was proposed due to the neutral hexose hydrolysis of vanillin glucoside. The subsequent dehydrogenation of vanillin produced vanillic acid. In addition, vanillin was detected in the distilled alcohol indicating its contribution to the aroma profile of beverages. It has been unknown that the vanillin in the distilled solution is derived from the vanillin produced during rice-koji and/or moromi mash fermentations.Electronic supplementary materialThe online version of this article (10.1186/s13568-018-0569-4) contains supplementary material, which is available to authorized users.
Monascus fungi are commonly used for a variety of food products in Asia, and are also known to produce some biologically active compounds. Since the use of Monascus is expected to increase in food industries, strain-level identification and management of Monascus will be needed in the near future. In the present study, random amplified polymorphic DNA (RAPD) analysis coupled with microchip electrophoresis was applied for this purpose. Evaluations of the analysis stability revealed that reproducible results could be obtained, although template DNA fragmentation could influence the resulting RAPD pattern. RAPD analysis using 15 Monascus strains consisting of four species, M. ruber, M. pilosus, M. purpureus, and M. kaoliang showed that each strain generated a unique RAPD pattern, which allows strain-level identification of Monascus. In addition, the phylogenetic tree constructed from RAPD patterns reflected M. ruber-M. pilosus and M. purpureus-M. kaoliang clusters inferred from both ITS and beta-tubulin gene sequences, which indicated that the RAPD pattern could reflect their phylogenetic traits to a certain extent. On the other hand, RAPD analysis did not support the monophyletic clustering of the four Monascus species used in this study, which suggests the necessity of reexamination of species boundaries in Monascus.
Abstract. Khao Mak is a sweet fermented rice-based dessert with a unique flavor profile commonly found throughout Thailand. The traditional starter culture (Look Pang) contains yeast, mold and herbs, which is used to ferment cooked glutinous rice. This research studied production of Khao Mak which resulted in volatile flavor compounds that were affected by rice varieties, including white glutinous rice (Kor Khor 6), Japanese rice (Hitomebore) and black glutinous rice (Kam Doi and Leum Phua). Total soluble solids (TSS) as degree Brix, pH, and alcohol concentrations were measured daily during the fermentation period. Volatile flavor compounds were separated and identified by gas chromatography mass spectrometry (GC-MS). At the end of the fermentation, samples had pH ranging from 3.91±0.16 to 4.30±0.09, total soluble solids of 32.65±1.65 to 44.02±1.72 Brix, and alcohol concentrations between 0.33±0.03 and 0.38±0.03% (v/v). The potent odors associated with Khao Mak were alcohol, wine-like, whiskey-like, solvent-like, sweet and fruity. The major volatile compounds, which have stimulant flavor in Khao Mak, included 1-propanal, 1-propanol-2-methyl, 1-butanal-3-methyl and acetic acid ethyl ester. Among all rice varieties tested, the white glutinous rice produced Khao Mak containing the highest TSS, alcohol concentrations followed by Hitomebore rice and black glutinous rice, respectively.
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